Project Periodic Report

PHOME 213390 Page 1

PROJECT PERIODIC REPORT

Grant Agreement number: 213390

Project acronym: PHOME

Project title: Photonic Metamaterials

Funding Scheme:

Periodic report: 1st □ 2nd □ 3rd □x 4th □ Period covered: from June 1, 2010 to August 31, 2011

Name, title and organisation of the scientific representative of the project's coordinator1:

Costas M. Soukoulis, Professor, IESL-FORTH, Heraklion, Crete, Greece

Tel: +30 2810 391303 & +30 2810 391547

E-mail: [email protected] Project website2 address: http://esperia.iesl.forth.gr/~ppm/PHOME/

1 Usually the contact person of the coordinator as specified in Art. 8.1. of the grant agreement 2 The home page of the website should contain the generic European flag and the FP7 logo which are available in electronic format at the Europa website (logo of the European flag: http://europa.eu/abc/symbols/emblem/index_en.htm ; logo of the 7th FP: http://ec.europa.eu/research/fp7/index_en.cfm?pg=logos). The area of activity of the project should also be mentioned. PHOME 213390 Page 2

Declaration by the scientific representative of the project coordinatorError: Reference source not found

I, as scientific representative of the coordinatorError: Reference source not found of this project and in line with the obligations as stated in Article II.2.3 of the Grant Agreement declare that:

. The attached periodic report represents an accurate description of the work carried out in this project for this reporting period;

. The project (tick as appropriate):

x□ has fully achieved its objectives and technical goals for the period; □ has achieved most of its objectives and technical goals for the period with relatively minor deviations3; □ has failed to achieve critical objectives and/or is not at all on schedule4.

. The public website is up to date, if applicable.

. To my best knowledge, the financial statements which are being submitted as part of this report are in line with the actual work carried out and are consistent with the report on the resources used for the project (section 3.6) and if applicable with the certificate on financial statement.

. All beneficiaries, in particular non-profit public bodies, secondary and higher education establishments, research organisations and SMEs, have declared to have verified their legal status. Any changes have been reported under section 5 (Project Management) in accordance with Article II.3.f of the Grant Agreement.

Name of scientific representative of the CoordinatorError: Reference source not found: Costas M. Soukoulis......

Date: ...... 10/ .....June/ 2010......

Signature of scientific representative of the CoordinatorError: Reference source not found: ...

......

3 If either of these boxes is ticked, the report should reflect these and any remedial actions taken. 4 If either of these boxes is ticked, the report should reflect these and any remedial actions taken. PHOME 213390 Page 3

Declaration by the scientific representative of the project coordinator1...... 2 Publishable summary...... 3 1. Project objectives for the period...... 4 2. Work progress and achievements during the period...... 5 3. Deliverables and milestones tables...... 19 4. Project management...... 20 5. Explanation of the use of the resources...... 21 6. Appendices...... 24

Publishable summary

The field of electromagnetic metamaterials is driven by fascinating and far-reaching theoretical visions such as, e.g., perfect lenses, invisibility cloaking, and enhanced nonlinearities. This emerging field has seen spectacular experimental progress in recent years. Yet, two major challenge remains: (i) realizing truly low-loss metamaterial structures. Linear gain inclusion in lossy metamaterials may provide a solution. (ii) Realizing true 3D metamaterial structures that will give negative n in different directions. Direct laser writing (DLW) may provide the solution of 3D isotropic metamaterials.

In the theory/modeling domain (WP1) we developed/improved various modeling tools: we extended the Finite Difference Time Domain (FDTD) code to lossy and to dispersive materials, we developed an inversion of the scattering data procedure, which enables to extract effective parameters (ε and μ) from the transmission data for chiral metamaterials, and we pursued the Microwave Studio, and FEMLAB commercial software, which gives the ability to treat very thin metals. In addition, we set out to take a systematic approach towards self-consistent calculations (using the semi-classical theory of lasing) for realistic gain materials that can be incorporated into or close to the NIMs, to reduce the losses at THz and optical frequencies. We developed, implement and used our own FDTD code to treat the field propagation and non-linear response of the gain material by coupling a set of auxiliary equations for the polarization oscillators and rate equations to the source-free Maxwell equations. Using FDTD simulations we studied the compensation of spatially distributed loss of metamaterials by differently spatially distributed inclusions of nonlinear gain for 2D model systems. A lot of simulations were made, with aim to find new 3D interconnected designs that can be fabricated by directed laser writing by our experimental partners. We have new blueprints for bulk connected photonic metamaterials and new chiral metamaterials that give negative index of refraction. Our experimental partners have fabricated and characterized chiral metamaterials at GHz, THz and telecom wavelengths. Finally, using transformation optics, various plasmonic structures have been designed and studied analytically, whereas, until now, only the numerical tool was available for the study of such plasmonic devices. Novel physical insights have been provided regards the resonant behavior of these nanostructures and the nanofocusing properties that can be expected with nanoparticle dimers. These nanostructures exhibit considerable nanofocusing capabilities: our theory predicts a field enhancement that can go beyond a factor of 104 over a broadband spectrum. PHOME 213390 Page 4

On the fabrication domain (WP2), as proposed, we have fabricated planar and non-planar new chiral metamaterials that give negative n at GHz frequencies. We have fabricated chiral metamaterials at THz frequencies and telecom wavelengths (1.5 micron). The telecom design is composed of pairs of twisted gold crosses using two successive electron-beam-lithography steps with intermediate planarization via a spin-on-dielectrics. We have fabricated a bulk photonic metamaterial with direct laser writing (DLW). DLW can be viewed as a 3D analogue of electron- beam lithography. Fabrication of polymer structures by this approach is standard. Infilling or coating of such polymer structures with metals is not standard at all. We have pursued chemical vapor deposition of silver and also infilling with gold with electroplating, and we were successful in both these two techniques. Coating approaches using chemical vapor deposition have successfully been developed. More recently, infilling with gold using an electroplating approach has turned out to be highly attractive. This work can be viewed as a possible first “real-world” application of the far-reaching concepts of electromagnetic metamaterials.

On the characterization and testing task (WP3): We performed a large number of free space transmission measurements in the 10 GHz, and 30 GHz regimes, using all our 1D and 2D fabricating structures, with both planar and non-planar chiral metamaterials. In the experiment, HP 8364B network analyzer with two Narda standard horn antennas measures the transmission coefficient. Four linear transmission coefficients, Txx, Tyx, Txy, and Tyy, are measured and the circular transmission coefficients, T+ +, T− +, T+ −, and T− − are converted from the linear transmission coefficients. Using the standard definitions of the polarization azimuth rotation,  =[arg(T+ +)−arg(T−

−)) /2, and the ellipticity,  = 0.5 arcsin{(|T+ +|−|T− −|)/(|T+ +|+|T− −|)}, of elliptically polarized light, we calculate the polarization changes in a linearly polarized wave incident on the cross-wire structures. We have used the numerically develop a retrieval procedure adopting the uniaxial bianisotropic model to calculate the effective parameters, ,  and n- and n+, of the chiral metamaterial design. We prove the existence of the negative index originating from the chirality  of the cross-wire metamaterial. As a comparison, the non-chiral version of the cross-wires pair design does not show any negative refractive index. We have optically characterized the chiral structures in the visible and near infrared and in the mid-infrared with circularly polarized incident light. Our measurements did not produce negative n at these high frequencies, but the strong optical rotation exists. Finally, we have fabricated and measured by THz spectroscopy the dynamic response of metamaterials, which give blue shift tenability and broadband tenability.

As promised, we created a web page for our consortium. The URL site is http://esperia.iesl.forth.gr/~ppm/PHOME/

Project objectives for the period The photonic metamaterials (PHOME) project has three scientific work packages (WP) and two extra ones, which are not scientific.

. WP1 deals with the modeling and the theory of photonic metamaterials (PMMs). Leader: FORTH . WP2 deals with the fabrication of photonic metamaterials (GHz to THz). Leader: Bilkent . WP3 deals with optical characterization and testing of photonic metamaterials. Leader: KIT . WP4 deals with the dissemination of the photonic metamaterials results. Leader: Imperial . WP5 deals with project management. Leader: FORTH

The objectives or tasks of the three work packages for the reporting period are the following: PHOME 213390 Page 5

. Objective: T1.1 Design of 3D connected PMMs and the extraction of the effective parameters  and n. . Objective: T1.2 Software and method development to model 3D chiral metallic nanostructures. . Objective: T1.3 Self-consistent calculations of incorporating gain and non-linearity in PMMs. Reduction of losses. . Objective: T1.4 Blueprints for thin-film isolators, for electro-optic modulators and optical switching. . Objective: T2.1 Optimization of chemical-vapor-deposition (CVD) apparatus for metal coating of 3D templates from the inside. . Objective: T2.2 Conversion of theoretical blueprints from WP1 into 3D polymer structures that can actually be made via direct laser writing and CVD coating. Test of the designs in larger structures, operating at GHz range. . Objective: T2.3 Optimization of successive electron-beam lithography, electron-beam evaporation, and planarization processes specifically for the novel materials and substrates involved. . Objective: T3.2 Linear optical characterization of all PMMs made in WP2 and parameter retrieval. . Objective: T3.3 Experiments on frequency conversion from tailored structures designed in WP1 and fabricated in WP2). . Objective: T3.4 Luminescence experiments on emitters embedded in or in the vicinity of PMMs under low (modified spontaneous emission) and high (gain) optical pumping

Work progress and achievements during the period We have all the pdf files of our published and submitted papers in our web site (http://esperia.iesl.forth.gr/~ppm/PHOME/) and one can find all the details of these results.

During the second year (June 1, 2010 to August 31, 2011) we have done an excellent job in accomplishing all the objectives for the reporting period (June 1, 2010 to August 31, 2011). In summary we describe what we have accomplished in the following three WPs:

Theory and Simulation

1. Development of the retrieval procedure for chiral metamaterials to extract the effective parameters ( and n) with and without substrate. 2. Find new designs for planar and non-planar chiral metamaterials that give an alternative root for negative index of refraction, and give strong optical activity. 3. We have demonstrated for the first time, theoretically and numerically, that the Casimir force can be repulsive by using chiral metamaterials. 4. Losses in metamaterials render the applications of such exotic materials less practical unless an efficient way of reducing them is found. We present two different techniques to reduce ohmic losses at both lower and higher frequencies, based on geometric tailoring of the individual magnetic constituents. We show that an increased radius of curvature, in general, leads to the least losses in metamaterials. Particularly at higher THz frequencies, bulky structures outperform the planar structures. 5. We have developed a self-consistent method to treat active materials in dispersive media as metamaterials. This method can help understand if introducing gain materials in metamaterials can reduce the losses. We are working to implement this method to work for 3D structures. PHOME 213390 Page 6

6. We have also presented new bulk designs that possess negative index of refraction at telecom frequencies and are easy to fabricate with direct laser writing, which is the most promising technique for the fabrication of truly 3D large scale optical metamaterials. 7. Using transformation optics, various plasmonic structures have been designed and studied analytically, whereas, until now, only the numerical tool was available for the study of such plasmonic devices. These nanostructures exhibit considerable nanofocusing capabilities: our theory predicts a field enhancement that can go beyond a factor of 104 over a broadband spectrum. 8. Radiation losses have been investigated both numerically and analytically in these devices. A good robustness relative to radiation losses has been predicted for structure dimension up to 400 nm. Nanostructures like a cylinder with a crescent-shaped cross-section or kissing cylinders are powerful light harvesting devices over a broadband spectrum, both in the visible and near infrared spectra.

Fabrication

1. A negative index of refraction due to three-dimensional chirality is demonstrated for a bilayered metamaterial based on pairs of mutually twisted planar metal patterns in parallel planes, which also shows negative electric and magnetic responses and exceptionally strong optical activity and circular dichroism. 2. Following our recent theoretical suggestion and microwave experiments, the UniKarl group has fabricated photonic metamaterials composed of pairs of twisted gold crosses and 4-U’s structures using two successive electron-beam-lithography steps and intermediate planarization via a spin-on dielectric. 3. Demonstration of a nonlinear photonic metamaterial by adding a nonlinear material (GaAs) to a split-ring-resonator array. 4. Fabricate structures that will be used for dynamic response of metamaterials at THz regime. They produce blueshift tenability and broadband simulation. 5. Direct laser writing (DLW) can be viewed as the three-dimensional analogue of electron-beam lithography. Fabrication of polymer structures by this approach is standard. In fact, we are using a commercial instrument from Nanoscribe GmbH (a collaboration with Carl Zeiss) that has emerged out of previous Karlsruhe work. Infilling or coating of such polymer structures with metals is not standard at all. We have pursued chemical-vapor deposition of silver and silver shadow evaporation. We have fabricated 2D metamaterials structures. 6. First realization of a three-dimensional gold-helix photonic metamaterial via direct laser writing into a positive-tone photoresist and subsequent infilling with gold via electroplating. 7. Finally, reaching beyond the original goals of PHOME first 3D invisibility cloaking structures have been realized – another striking demonstration of the future possibilities of our direct laser writing approach for making 3D metamaterials at optical frequencies.

Measurements

1. Free space transmission measurements of 1D and 2D chiral structures, at GHz frequencies, discovery of strong optical activity and negative refraction. 2. We have fabricated twisted-cross photonic metamaterials that exhibit strong and pure optical activity in a fairly large spectra range around 1.3 micron wavelength. In addition, we have used a different design (4-U’s) and exhibit strong activity at 3 micron wavelength. 3. Transmission properties of the bilayered form of the metamaterial for left-handed (LCP) and right-handed (RCP) circular polarizations. The structure shows exceptionally strong circular dichroism and strong rotation angle. Pure optical activity, i.e., polarization azimuth rotation PHOME 213390 Page 7

without any change of ellipticity, is achieved between resonances, where the absolute rotation is about 800° per wavelength (6 GHz) and about 400° per wavelength (105 THz) for 4-U’s and about 60° per wavelength (220 THz) for crosee wires. 4. We have fabricated many split-ring resonator (SRR) structures on crystalline GaAs semiconductor substrates. We find strong coupling between the electromagnetic near-fields of the split rings and the underlying GaAs substrate, resulting in measured second-harmonic generation (SHG) that is about 25 times stronger than that we have previously found for split- ring-resonator arrays on glass substrate. 5. Such strong interaction between the SRRs and the underlying semiconductor is also crucial for compensating metamaterial losses by introducing gain. In our corresponding design studies, we have considered SRR on top of a thin gain layer. We using electron-beam lithography have also fabricated many corresponding structures. Various gain layers are available to us from cooperation partner, i.e., single quantum wells, three quantum wells, layers of quantum dots, or thin bulk films. A dedicated low-temperature femtosecond pump/probe experiment has been assembled. In this setup, pulses centered around 800-nm wavelength derived from a Ti:sapphire laser are used as the optical pump. Average powers around 100 mW focused to spots on the sample with diameters around 20-30 µm enable extremely strong pumping conditions, for which quantum well (QW) gain is expected. Fortunately, under these intense, essentially continuous- wave, pumping conditions, no sample deterioration has been observed. The probe pulses are derived from an optical parametric oscillator (OPO) that is tunable at around 1500-nm wavelength. The setup allows for detecting pump-induced changes in transmittance. The samples are cooled in a He-flow cryostat to increase the anticipated material gain. However, under conditions of intense pumping and at low temperatures, we have so far not found any “SPASING” action, which would be a clear-cut proof of complete compensation of metamaterial losses by the gain. 6. THz time-domain spectroscopy is used to probe the electromagnetic properties of metamaterials, that were fabricated within the PHOME, which are dynamically photo excited, using synchronized femtosecond near-infrared laser pulses. Blushift tunability of the metamaterials and a broadband phase tenability at about 45°. These results cab be used as a switching effect at THz frequencies. 7. We have fabricated and demonstrated metamaterials based enhanced transmission through subwavelength apertures. PHOME 213390 Page 8

WP1: Theory and Modeling

. A summary of progress towards objectives and details for each task

Work package 1 (WP1) is devoted to new design concepts and their simulations; these designs shall lead, among other goals, to optimized low-loss, broad bandwidth PMMs to be fabricated in WP2 and characterized in WP3. Development of new software and methods to model 3D chiral metamaterials will be also part of the WP1 efforts. In addition, we will also develop a self- consistent theory of incorporating gain or nonlinearity in PMMs. We have developed the 2D code for incorporating gain in metamaterials. We are working to implement the 3D code, which needs a lot of computer memory. Furthermore, blueprints for 3D metamaterials have been developed that acknowledge the conceptual boundary conditions of the novel corresponding fabrication approaches pursued in WP2. We have addressed all the four tasks T1.1 (Design of 3D connected PMMs and the extraction of the effective parameters ( and n), T1.2 (Software and method development to model 3D chiral metallic nanostructures), T1.3 (Self-consistent calculations of incorporating gain and non-linearity in PMMs. Reduction of losses), and T1.4 (Blueprints for thin-film isolators, for electro-optic modulators and optical switching) and we have substantial progress in the second year. We have followed the traditional way to reduce losses by eliminating the sharp corners, and also by geometric tailoring we found ways to reduce the losses. In addition, our Imperial partners have pursue another way to use transformation optics to design and study analytically novel plasmonic metamaterials structures showing nanofocusing abilities, (for details see the second year report).

. Highlight clearly significant results

 First self-consistent calculation of 3D metamaterials with gain (PRB 2010, ref. 25; Opt. Expr. 2010, ref. 7; Opt. Expr. 2011, ref. 28; Phot. & Nanostr. 2011, ref. 31).  Design of planar and non-planar chiral metmaterials that give negative n and strong optical activity (Opt. Lett. 2010, ref. 1; Opt. Lett. 2010, ref. 6; APL 2010, ref. 22; Opt. Expr. 2010, ref. 24; Opt. Expr. 2011, ref. 34).  Design of intra-connected 3D isotropic bulk negative index photonic metamaterial (Science 2010, ref. 10; Nature Photonics 2011 ref. 20).  Reducing losses in photonic metamaterials (Science 2010, ref. 10; Nature Photonics 2011 ref. 20).  Design of Electromagnetic Induced Transparency (EIT) to reduce the speed of light and losses (APL 2010, ref. 26; PRL 201, ref. 29).  Based on conformal transformation, a general strategy is proposed to design plasmonic capable of an efficient harvesting of light over a broadband spectrum (Nano Letters, 2010, ref. 59).  The physics of the interaction between plasmonic nanoparticles has been revisited with transformation optics. Novel physical insights have been provided regards the resonant behavior of these nanostructures and the nanofocusing properties that can be expected with nanoparticle dimers. We use 2D wedge-like structures, tapered wave guides, open nanocrescents or overlapping cylinders than can be able to exhibit a singularity, which may give rise to a divergence of the electric field, even in presence of dissipation losses. This singular behavior had not been pointed out in the past and can be of great interest for single molecule detection. (ACS Nano 2011, ref. 51; PRB 2011, ref. 52; ACS Nano 2011, ref. 53; PRB 2010, ref. 55; Nano Lett. 2010, ref. 56; New J. Phys. 2010, ref. 57; PRB 2010, ref. 58). PHOME 213390 Page 9

WP2: Fabrication of photonic metamaterials

Work package 2 (WP2) is devoted to a systematic study of materials and processing methods to optimize the quality of micro- and nanofabricated PMMs. Furthermore; novel fabrication approaches shall be explored for 3D structures. The latter idea is very risky, but it is worth pursuing, especially in the spirit of the FET program, which supports exploitation of ideas that can open new possibilities and set new trends for feature research. As PMMs are scaled to higher frequencies, the quality of materials and fabrication becomes of increasing importance. Because PMMs are based on resonant micro and nanostructured conductors, fabrication tolerance and surface quality are crucial. Our team brings extraordinary fabrication capabilities, with access to nearly all state-of-the-art fabrication facilities, including electron- and focused-ion-beam (FIB) lithography, as well as direct laser writing for true 3D structures. During the first two years, we have performed a careful study of the various figures-of-merit of NIM prototypes as a function of fabrication conditions, including material deposition conditions, annealing and surface smoothness, and quality as characterized by atomic-force microscopy. We have addressed the three tasks of WP2, T2.1 (Optimization of chemical-vapor-deposition (CVD) apparatus for metal coating of 3D templates from the inside), T2.2 (Conversion of theoretical blueprints from WP1 into 3D polymer structures that can actually be made via direct laser writing and CVD coating. Test of the designs in larger structures, operating at GHz range), and T2.3 (Optimization of successive electron-beam lithography, electron-beam evaporation, and planarization processes specifically for the novel materials and substrates involved). In detail, as proposed, we have pursued two alternative and complementary fabrication approaches for three-dimensional (3D), i.e., non-planar, photonic metamaterials: (i) Direct laser writing and (ii) stacking of layers made via electron-beam lithography. While we have considered the novel approach (i) as very risky at the time of the proposal, it has delivered several results already and even unexpected variations of this approach are emerging from KIT.

 First realization of a three-dimensional gold-helix photonic metamaterial as broadband circular polarizer (Physics Today 2010, ref. 5, Science 2010, ref. 10; Nature Photonics 2011, ref. 20).  Demonstration of a photonic 3D photonic metamaterial made via 3D direct laser writing (Opt. Matt. Expr. 2011, ref. 18; Nature Photonics 2011, ref. 20).  First demonstration of 3D invisibility cloak at optical wavelengths made via 3D direct laser writing (Physics Today 2010, ref. 5; Opt. Expr. 10, ref. 8; Opt. Lett. 2011, ref. 13; Opt. Expr. 2011, ref. 14; Opt. Expr. 2010, ref. 3).  Fabrications of planar chiral metamaterials that give negative n and strong optical activity at THz frequencies (Opt. Lett. 2011, ref. 1; Nature Photonics 2011, ref. 20).  Dynamic response of metamaterials in the THz regime: Broadband blue-shift switch (PRL. 2011, ref. 27).  Design and fabricated a planar metamaterial that exhibits Electromagnetic Induced Transparency (EIT) at around 10 GHz with metals and superconductors (APL 2010, ref. 26; PRL 201, ref. 29).  Demonstration of a nonlinear photonic metamaterial by adding a nonlinear material (GaAs) to a split-ring-resonator array (Opt. Expr. 2010, ref. 7). PHOME 213390 Page 10

 Metamaterials based enhanced transmission through sub-wavelength apertures (J. of Nanophotonics 2011, ref. 45; J. of Appl. Phys. 2011, ref. 35; Opt. Expr. 2010, ref. 38; Phys. Stat. Solidi 2010, ref. 39; Opt. Lett. 2011, ref. 47 ).  Design and fabricated metamaterials absorbers (Opt. Expr. 2011, ref. 30; J. of Appl. Phys. 2010, ref. 38; IEEE 2011, ref. 48).

WP3: Optical characterization and testing

Work package 3 (WP3) is devoted to the characterization of the metamaterial structures made in WP2. The fabrication in WP2 is obviously intimately interwoven with the optical characterization and testing in WP3. Thus below, the significant results are the same as in WP2. This requires innovative approaches regarding the retrieval of optical constants from experimentally accessible parameters. The experiments include THz time-domain spectroscopy, optical transmittance and reflectance spectroscopy, laser based interferometry, near-field optical spectroscopy, as well as nonlinear optical spectroscopy. These measurements will be accompanied by thorough theoretical analysis and modeling emerging from WP1. With the combined efforts of Work packages 1-3, photonic metamaterials could make the step from sub-wavelength thickness films towards truly 3D materials. If this risky enterprise is successful, the step to ICT relevant devices and demonstrators is small. Examples are “poor man’s” optical isolators, optical switching, and electro-optic modulators. During the first two years, we have address all the tasks of WP3, T3.1 (Optical characterization of all PMMs made in WP2), T3.2 (Linear optical characterization of all PMMs made in WP2 and parameter retrieval), T3.3 (Experiments on frequency conversion from tailored structures designed in WP1 and fabricated in WP2), T3.4 (Luminescence experiments on emitters embedded in or in the vicinity of PMMs under low (modified spontaneous emission) and high (gain) optical pumping).

Much of the optical metamaterial characterization performed by KIT in this project is not standard at all. This comprises the following set-ups:

. Quantitative optical spectroscopy on individual metamaterial elements (“photonic atoms”). We have put much effort into further optimizing data quality as well as into reducing measurement times by replacing the pervious mechanical translation stages by piezoelelectric actuators along all thee spatial axes. This step has allowed extensive studies on “photonic molecules” of SRR (made via electron-beam lithography) in which we have systematically investigated the effects of SRR distance and orientation. As outlined above, this work is important for avoiding break-up effects in metamaterials incorporating optical gain. . Optical spectroscopy with circularly polarized incident light in the visible and near- infrared. Our corresponding home-built set-up has been further improved, now also allowing for analysis of the state of polarization emerging from the metamaterial sample. . Optical spectroscopy with circularly polarized incident light in the mid-infrared. As described in the proposal, we are operating two commercial Fourier-transform microscopy- spectrometers allowing for spectroscopy on small samples up to wavelengths of about 10 µm. These instruments did not allow for circular polarization of the incident light at all – which, however, is crucial for characterizing three-dimensional chiral metamaterial structures. Thus, we have custom modified these instruments: A home-made compact holder encompasses a linear CaF2 “High Extinction Ratio” holographic polarizer and a super- PHOME 213390 Page 11

achromatic quarter-wave plate that can be rotated from the outside of the microscope. The custom-made MgF2 based super-achromatic quarter-wave plate (Bernhard Halle Nachfl.) has a phase error below only ± 14 % in the entire spectral range from 2.5 to 7.0 µm wavelength of light. This modification allows for conveniently adjusting left and right- handed circular polarization of the incident light. Furthermore, we have modified the reflective ×36 Cassegrain optics with NA=0.5 by introducing a small diaphragm such that the full opening angle of the light incident onto the sample is reduced to about 5 degrees. By tilting the sample we achieve actual normal incidence of light onto the sample. . A dedicated low-temperature femtosecond pump/probe experiment has been assembled. In this setup, pulses centred around 800-nm wavelength derived from a Ti:sapphire laser are used as the optical pump. Average powers around 100 mW focused to spots on the sample with diameters around 20-30 µm enable extremely strong pumping conditions, for which quantum well (QW) gain is expected. Fortunately, under these intense, essentially continuous-wave, pumping conditions, no sample deterioration has been observed. The probe pulses are derived from an optical parametric oscillator (OPO) that is tunable at around 1500-nm wavelength. The setup allows for detecting pump-induced changes in transmittance. The samples are cooled in a He-flow cryostat to increase the anticipated material gain. This set up will be used to see if we can compensate the losses by gain material.

 First realization of a three-dimensional gold-helix photonic metamaterial as broadband circular polarizer (Physics Today 2010, ref. 5, Science 2010, ref. 10; Nature Photonics 2011, ref. 20).  Demonstration of a photonic 3D photonic metamaterial made via 3D direct laser writing (Opt. Matt. Expr. 2011, ref. 18; Nature Photonics 2011, ref. 20).  First demonstration of 3D invisibility cloak at optical wavelengths made via 3D direct laser writing (Physics Today 2010, ref. 5; Opt. Expr. 10, ref. 8; Opt. Lett. 2011, ref. 13; Opt. Expr. 2011, ref. 14; Opt. Expr. 2010, ref. 3).  Fabrications of planar chiral metamaterials that give negative n and strong optical activity at THz frequencies (Opt. Lett. 2011, ref. 1; Nature Photonics 2011, ref. 20).  Dynamic response of metamaterials in the THz regime: Broadband blue-shift switch (PRL. 2011, ref. 27).  Design and fabricated a planar metamaterial that exhibits Electromagnetic Induced Transparency (EIT) at around 10 GHz with metals and superconductors (APL 2010, ref. 26; PRL 201, ref. 29).  Demonstration of a nonlinear photonic metamaterial by adding a nonlinear material (GaAs) to a split-ring-resonator array (Opt. Expr. 2010, ref. 7).  Metamaterials based enhanced transmission through sub-wavelength apertures (J. of Nanophotonics 2011, ref. 45; J. of Appl. Phys. 2011, ref. 35; Opt. Expr. 2010, ref. 38; Phys. Stat. Solidi 2010, ref. 39; Opt. Lett. 2011, ref. 47 ).  Design and fabricated metamaterials absorbers (Opt. Expr. 2011, ref. 30; J. of Appl. Phys. 2010, ref. 38; IEEE 2011, ref. 48). PHOME 213390 Page 12

WP4: Dissemination of the photonic metamaterials results

In the current reporting period we had a large number of publications and invited talks at conferences and institutions, where we advertised the PHOME results. Below we mention some steps, planned or done, towards dissemination and use of the PHOME results..  We have created a web page where we plan to put our articles on PMMs and our main results. This page is linked to the CORDIS sites, it gives links to the main groups working on the area of metamaterials and it will be connected also to the main metamaterial related web pages in the near future.  We present and we will continue to present the PHOME results through publications, colloquia, and participations to conferences and workshops.  We have organized sessions devoted to PMMs at international conferences (SPIE 2010, San Diego, USA, August 2010; Metamaterials Congress Conference, Karlsruhe, Germany September 2010; International Workshop on Photonic and Electromagnetic Crystal Structures, (PECS-IX), Granada, Spain, September 2010; Medi-Nano 3, Belgrade, Serbia, October 2010; 3nd International Workshop on Theoretical and Computational Nanophotonics (TaCoNa-Photonics), Bad Honnef, Germany, December 2010; The 3rd European Topical Meeting on Nanophotonics and Metamaterials, NanoMeta-2011, Seefeld, Tirol, Austria, January 2011; 41st Winter Colloquium on the Physics of Quantum Electronics (PQE), Snowbird (U.S.A.), January 2011; SPIE Photonics Europe 2011, “Metamaterials” Prague, Czech Republic, April 2011; International Conference on Materials for Advanced Technologies (ICMAT 2011), Singapore, June 2011; SPIE 2011, San Diego, USA, August 2011), where PHOME results will be advertised.  We have organized a conference on Photonic Metamaterials at Rethymnon, Crete, Greece, in June 2011. In this conference new results were presented and were discussed what are the challenges and the future of the photonic metamaterials. See the website http://cmp.physics.iastate.edu/wavepro/ and all the talks are posted in this site.  We have organized a European school devoted to “Experimental characterization of electromagnetic metamaterials”, Heraklion, Crete, December 13-17 2010, where many young researchers had the chance to familiarize themselves with the field of photonic metamaterials.  The experimental group of Karlsruhe is in discussion with industries about potential applications of PMMs as optical isolators.  We plan to send any information (high level publication, appearances of FET projects etc.) to the DG Information Society

Below we list publications and the invited talks and seminars on photonic metamaterials, which took place during the current reporting period. The publications are listed also at the project webpage, at http://esperia.iesl.forth.gr/~ppm/PHOME/

Puclications:

1. M. Decker, R. Zhao, C.M. Soukoulis, S. Linden, and M. Wegener, Twisted split-ring-resonator photonic metamaterial with huge optical activity, Opt. Lett. 35, 1593 (2010). 2. M. Burresi, D. Diessel, D. van Osten, S. Linden, M. Wegener, and L. Kuipers, Phase-sensitive near-field optical microscopy on negative-index metamaterials, Nano Lett. 10, 2480 (2010). 3. T. Ergin, J.C. Halimeh, N. Stenger, and M. Wegener, Optical microscopy of 3D carpet cloaks: ray- tracing simulations, Opt. Express 18, 20535 (2010). PHOME 213390 Page 13

4. L. Shao, M. Ruther, S. Linden, S. Essig, K. Busch, J. Weissmüller, and M. Wegener, Electrochemical Modulation of Photonic Metamaterials, Adv. Mater. 22, 5173 (2010). 5. M. Wegener and S. Linden, Shaping Optical Space with Metamaterials, Physics Today 63, 32 (2010). 6. D. Diessel, M. Decker, S. Linden, and M. Wegener, Near-field optical experiments on low-symmetry split-ring-resonator arrays, Opt. Lett. 35, 3661 (2010). 7. N. Meinzer, M. Ruther, S. Linden, C.M. Soukoulis, G. Khitrova, J. Hendrickson, J.D. Olitzky, H.M. Gibbs, and M. Wegener, Arrays of Ag split-ring resonators coupled to InGaAs single-quantum-well gain, Opt. Express 18, 24140 (2010). 8. R. Schmied, J.C. Halimeh, and M. Wegener, Conformal carpet and grating cloaks, Opt. Express 18, 24361 (2010). 9. G. Boudarham, N. Feth, V. Myroshnychenko, S. Linden, O. Stephan, C. Colliex, J. Garcia de Abajo, M. Wegener, and M. Kociak, Spectral Imaging of Individual Split-Ring Resonators, Phys. Rev. Lett. 105, 255501 (2010). 10. C.M. Soukoulis and M. Wegener, Optical Metamaterials: More Bulky and Less Lossy, Science 330, 1633 (2010). 11. M. Ruther, L. Shao, S. Linden, J. Weissmüller, and M. Wegener, Electrochemical Restructuring of Plasmonic Metamaterials, Appl. Phys. Lett. 98, 013112 (2011). 12. F.B.P. Niesler, N. Feth, S. Linden, and M. Wegener, Second-harmonic optical spectroscopy on split- ring-resonator arrays, Opt. Lett. 36, 1533 (2011). 13. J. Fischer, T. Ergin, and M. Wegener, Three-dimensional polarization-independent visible-frequency carpet invisibility cloak, Opt. Lett. 36, 2059 (2011). 14. J.C. Halimeh, R. Schmied, and M. Wegener, Newtonian photorealistic ray tracing of grating cloaks and correlation-function-based cloaking-quality assessment, Opt. Express 19, 6078 (2011). 15. M. Decker, N. Feth, C.M. Soukoulis, S. Linden, and M. Wegener, Retarded long-range interaction in split-ring-resonator square arrays, Phys. Rev. B 84, 085416 (2011). 16. J. Müller, T. Ergin, N. Stenger, and M. Wegener, Doppelt sehen oder gar nicht sehen, Physik Journal 3, 16 (2011). 17. M.J. Huttunen, G. Bautista, M. Decker, S. Linden, M. Wegener, and M. Kauranen, Nonlinear chiral imaging of subwavelength-sized twisted-cross gold nanodimers, Opt. Mater. Express 1, 46 (2011). 18. J. Fischer and M. Wegener, Three-dimensional direct laser writing inspired by stimulated-emission- depletion microscopy, Opt. Mater. Express 1, 614 (2011). 19. T.J.A. Wolf, J. Fischer, M. Wegener, and A.-N. Unterreiner, Pump-probe spectroscopy on photoinitiators for stimulated-emission-depletion optical lithography, Opt. Lett., in press (2011). 20. C.M. Soukoulis and M. Wegener, Past achievements and future challenges in the development of three- dimensional photonic metamaterials, Nature Photon., (Published online 17 July 2011). 21. A. Frölich and M. Wegener, Spectroscopic characterization of highly doped ZnO by atomic-layer deposition for three-dimensional infrared metamaterials, Opt. Mater. Express, in press (2011). 22. Z. Li, R. Zhao, Th. Koschny, M. Kafesaki, E. Colak, H. Caglayan, E. Ozbay and C. M. Soukoulis, “Chiral metamaterials with negative refractive index based on Four-U-SRRs resonators,” Appl. Phys. Lett. 97, 081901 (2010). 23. R. S. Penciu, M. Kafesaki, Th. Koschny, E. N. Economou and C. M. Soukoulis, “Magnetic response of nanoscale left-handed metamaterials,” Phys. Rev. B 81, 235111 (2010). 24. R. Zhao, Th. Koschny and C. M. Soukoulis, “Chiral memamaterials: Retrieval of the effective parameters with and without substrate,” Opt. Express 18, 14553 (2010). 25. A. Fang, Th. Koschny, and C. M. Soukoulis, “Self-consistent calculations of loss compensated fishnet metamaterials,” Phys. Rev. B 82, 121102 (R) (2010). 26. Lei Zhang, P. Tassin, Th. Koschny, C. Kurter, S. M. Anlage and C. M. Soukoulis, “Large group delay in a microwave metamaterial analog of Electromagnetic Induced Transparency,” Appl. Phys. Lett. 97, 241904 (2010). 27. N. H. Shen, M. Massaouti, M. Gokkavas, J. M. Manceau, E. Ozbay, S. Tzortzakis, M. Kafesaki, and C. M. Soukoulis, “Optical implemented broadband blue-shift switch in the terahertz regime,” Phys. Rev. Lett. 106, 037403 (2011). 28. A. Fang, Z. Huang Th. Koschny, and C. M. Soukoulis, “Overcoming losses of a split ring resonator array with gain,” Opt. Express 19, 12688 (2011). PHOME 213390 Page 14

29. C. Kurter, P. Tassin, Lei Zhang, Th. Koschny, A. P. Zhuravel, A. V. Ustinov, S. M. Anlage and C. M. Soukoulis, “Classical analogue of Electromagnetic Induced Transparency with a metal/superconductor hybrid metamaterial,” Phys. Rev. Lett. 107, 043901 (2011). 30. K. B. Alici, A. B. Turhan, C. M. Soukoulis, and E. Ozbay, “Optically thin composite resonant absorber at the near-infrared band: a polarization independent and spectrally broadband configuration,” Opt. Express 19, 14260 (2011). 31. A. Fang, Z. Huang Th. Koschny, and C. M. Soukoulis, “Loss compensated negative index materials at optical wavelengths,” Photonics and Nanostructures 9, xxxx (2011). 32. H. Caglayan and Ekmel Ozbay, “Observation of cavity structures in composite metamaterials,” Journal of Nanophotonics 4, 041790 (2010). 33. Ekmel Ozbay, “Photonic Metamaterials: Science Meets Magic,” IEEE Photonics Journal 2, 249 (2010). 34. E. Saenz, K. Guven, E. Ozbay, I. Ederra, and R. Gonzalo, “Decoupling of Multifrequency Dipole Antenna Arrays for Microwave Imaging Applications,” Inter. Journal of Antennas and Propagation, Appl. Phys. 2010, 843624 (2010). 35. E. Colak, A. O. Cakmak, A. E. Serebryannikov, and E. Ozbay, “Spatial filtering using dielectric photonic crystals at beam-type excitation," J. Appl. Phys. 108, 113106 (2010). 36. A. E. Serebryannikov, P.V. Usik, and E. Ozbay, “Defect-mode-like transmission and localization of light in photonic crystals without defects,” Phys. Rev. B 82, 165131 (2010). 37. K. B. Alici, F. Bilotti, L. Vegni, and E. Ozbay, “Experimental verification of metamaterial based subwavelength microwave absorbers,” J of Appl. Phys. 108, 083113 (2010). 38. A. O. Cakmak, E. Colak, A. E. Serebryannikov, and E. Ozbay, "Unidirectional transmission in photonic- crystal gratings at beam-type illumination," Optics Express 18, 22283 (2010). 39. K. B. Alici, and E. Ozbay, “Metamaterial inspired enhanced far-field transmission through a subwavelength nano-hole,” Physica Status Solidi RRL 4, 286 (2010). 40. H. Caglayan, S. Cakmakyapan, S. A. Addae, M. A. Pinard, D. Caliskan, K. Aslan, and Ekmel Ozbay, “Ultrafast and and sensitive bioassay using SRR structures and microwave heating” Appl. Phys. Lett. 97, 093701 (2010). 41. S. Cakmakyapan, A. E. Serebryannikov, H. Caglayan, and Ekmel Ozbay, "One-way transmission through the subwavelength slit in nonsymmetric metallic gratings," Optics Letters 35, 2597 (2010). 42. K. B. Alici, A. E. Serebryannikov, and E. Ozbay, "Radiation properties and coupling analysis of a metamaterial based, dual polarization, dual band, multiple split ring resonator antenna," J. of Electromagn. Waves and Appl. 24, 1183 (2010). 43. A. E. Serebryannikov, and Ekmel Ozbay “Non-ideal multifrequency cloaking using strongly dispersive materials,” Physica B 405, 2959 (2010). 44. M. Mutlu, A. E. Akosman, A. E. Serebryannikov, and Ekmel Ozbay, "Asymmetric transmission of linearly polarized waves and polarization angle dependent wave rotation using a chiral metamaterial," Optics Express 19, 14290 (2011). 45. L. Sahin, K. Aydin, G. T. Sayan and Ekmel Ozbay, “Enhanced transmission of electromagnetic waves through split-ring resonator-shaped apertures,” J. of Nanophotonics 5, 051812 (2011). 46. M. Mutlu, A. E. Akosman, A. E. Serebryannikov, and Ekmel Ozbay, “Asymmetric chiral metamaterial circular polarizer based on four U-shaped split ring resonators,” Optics Letters 36, 1653 (2011). 47. Zhaofeng Li, K. B. Alici, E. Colak, and Ekmel Ozbay, “Complementary chiral metamaterials with giant optical activity and negative refractive index,” Appl. Phys. Lett. 98, 161907 (2011). 48. F. Bilotti, A. Toscano, K. B. Alici, Ekmel Ozbay, and L. Vegni “Design of Miniaturized Narrowband Absorbers Based on Resonant-Magnetic Inclusions,” IEEE Transactions on Electromagnetic Compatibility 53, 63 (2011). 49. K. B. Alici, A. E. Serebryannikov, and Ekmel Ozbay “Photonic magnetic metamaterial basics,” Photonics and Nanostructures 7, 15 (2011). 50. S. Cakmakyapan, H. Caglayan, A. E. Serebryannikov, and E. Ozbay, "Experimental validation of strong directional selectivity in nonsymmetric metallic gratings with a subwavelength slit," Appl. Phys. Lett. 98, 051103 (2011). 51. A. Aubry, D. A. Lei, S. A. Maier, and J. B. Pendry, “Plasmonic Hybridization between Nanowires and a Metallic Surface: A Transformation Optics Approach,” ACS NANO 5, 3293 (2011). PHOME 213390 Page 15

52. Yu Luo, A. Aubry, and J. B. Pendry, “Electromagnetic contribution to surface-enhanced Raman scattering from rough metal surfaces: A transformation optics approach,” Phys. Rev. B 83, 155422 (2011). 53. Dang Yuan Lei, A. Aubry, Yu Luo, S. A. Maier and J. B. Pendry. “Plasmonic Interaction between Overlapping Nanowires,” ACS NANO 5, 597 (2011). 54. A. Aubry, Dang Yuan Lei, S. A. Maier and J. B. Pendry. “Interaction between Plasmonic Nanoparticles Revisited with Transformation Optics,” Phys. Rev. Lett. 105, 233901 (2010). 55. A. Aubry, Dang Yuan Lei, Stefan A. Maier, and J. B. Pendry, “Conformal transformation applied to plasmonics beyond the quasistatic limit,” Phys. Rev. B 82, 205109 (2010). 56. Yu Luo, J. B. Pendry and A. Aubry, “Surface Plasmons and Singularities,” Nano Letters 10 4186 (2010). 57. Dang Yuan Lei, A. Aubry, S. A Maier and J. B Pendry “Broadband nano-focusing of light using kissing nanowires,” New J. of Phys. 12, 093030 (2010). 58. A. Aubry, Dang Yuan Lei, Stefan A. Maier, and J. B. Pendry, “Broadband plasmonic device concentrating the energy at the nanoscale: The crescent-shaped cylinder,” Phys. Rev. B 82, 125430 (2010). 59. A. Aubry, Dang Yuan Lei, A. I. Fernandez-Domínguez, Y. Sonnefraud, S. A. Maier and J. B. Pendry “Plasmonic Light-Harvesting Devices over the Whole Visible Spectrum,” Nano Letters 10 2574 (2010).

Conference presentations (only Invited Talks listed here)

1. M. Kafesaki, ”5th Forum on New Materials in CIMTEC 2010 Conference,” Florence, Italy, June 2010 2. M. Kafesaki, ”12th International Conference on Transparent Optical Networks (ICTON),” Munich, Germany, June 2010. 3. M. Kafesaki, “Summer school on ”Mesoscopic Physics in Complex Media”, Cargese, Corsica, July 2010. 4. M. Kafesaki, “SPIE Optics and Photonics conference on “Nanoscienc+Engineering”, San Diego, USA, August 2010. 5. M. Kafesaki, “Metamaterials 2010”, Karlsruhe, Germany, September 2010. 6. M. Kafesaki, ”3rd Mediterranean Conference on Nanophotonics,” (Medi-Nano 3), Belgrade, Serbia, October 2010. 7. M. Kafesaki, "International Workshop on Theoretical and Computational Nanophotonics 2010" (TaCoNa-Photonics2010), Bad Honnef, Germany, November 3-5, 2011. 8. M. Kafesaki, "Progress In Electromagnetics Research Symposium 2011" (PIERS 2011), Marrakesh, Morocco, March 20-23, 2011. 9. M. Kafesaki, Annual international conference "Days of Diffraction" (Metamaterials Workshop), St. Petersburg, Russia, May 30 - June 3, 2011. 10. M. Kafesaki, International Symposium on Wave Propagation: From Electrons to Photonic Crystals and Metamaterials, Crete, Greece, June 8-11, 2011. 11. M. Kafesaki, International Conference on Materials for Advanced Technologies (ICMAT 2011), Singapore, June 26 – July 1, 2011. 12. M. Kafesaki, "Moscow International Symposium on Magnetism" (MISM), Moscow, Russia, August 21 – 25, 2011. 13. C.M. Soukoulis, SPIE Optics and Photonics, San Diego, Ca, USA, August 1-6, 2010 (Plenary Talk). 14. C. M. Soukoulis, International Conference on Electromagnetic Metamaterials IV: New Directions in Active and Passive Metamaterials, Santa Ana Pueblo, New Mexico, August 11-12, 2010. 15. C. M. Soukoulis, Fourth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials 2010), Karlsruhe, Germany, September 12-16, 2010. 16. C. M. Soukoulis, Metamaterials Doctoral School, Bringing Gain to Metamaterials, Karlsruhe, Germany, September 17-18, 2010 (Tutorial). 17. C. M. Soukoulis, International Workshop on Photonic and Electromagnetic Crystal Structures, (PECS- IX), Granada, Spain, September 26-30, 2010. 18. C. M. Soukoulis, International Symposium on Wave Propagation: From Electrons to Photonic Crystals and Metamaterials, Crete, Greece, June 8-11, 2011. PHOME 213390 Page 16

19. C. M. Soukoulis, International Conference on Materials for Advanced Technologies (ICMAT 2011), Singapore, June 26 – July 1, 2011. 20. C.M. Soukoulis, SPIE Optics and Photonics, San Diego, Ca, USA, August 21-25, 2011. 21. M. Wegener, Photonic metamaterials and transformation optics, iNANO International summer school in advanced photonics, Fuglsocenter (Denmark), September 3-7, 2010. 22. N. Stenger, T. Ergin, J.C. Halimeh, and M. Wegener, 3D Optical Carpet Cloak, Fourth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics Metamaterials 2010, Karlsruhe (Germany), September 13-16, 2010. 23. S. Linden, N. Feth, M. Decker, M. König, J. Niegemann, K. Busch, and M. Wegener, Electromagnetic interaction of split-ring resonators: The role of separation and relative orientation, Fourth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics Metamaterials 2010, Karlsruhe (Germany), September 13-16, 2010. 24. M. Wegener, Photonic Metamaterials: Recent Progress, PECS IX – The 9th International Photonic & Electromagnetic Crystal Structures Meeting, Granada (Spain), September 26-30, 2010. 25. M. Wegener, Photonic Metamaterials, “Micro-Optics” Meeting, European Optical Society Annual Meeting, Paris (France), October 26-28, 2010. 26. N. Meinzer, M. Ruther, S. Linden, C.M. Soukoulis, G. Khitrova, J. Hendrickson, J.D. Olitzky, H.M. Gibbs, and M. Wegener, Plasmonic Metamaterials Coupled to Single-Quantum-Well Gain, 41st Winter Colloquium on the Physics of Quantum Electronics (PQE), Snowbird (U.S.A.), January 2-6, 2011. 27. M. Wegener, 3D Metamaterials and Transformation Optics, The 3rd International Topical Meeting on Nanophotonics and Metamaterials, NANOMETA 2011, Seefeld (Austria), January 3-6, 2011. 28. M. Wegener, Three-dimensional diffraction-unlimited direct-laser-writing optical lithography, International Workshop “Laser Based Micromanufacturing – From Surface Structuring to Metamaterials”, Erlangen (Germany), January 10-11, 2011. 29. T. Ergin, N. Stenger, J.C. Halimeh, and M. Wegener, 3D invisibility cloaks at optical frequencies, International Conference Photonics West, San Francisco (U.S.A.), January 22-27, 2011. 30. M. Wegener, 3D Photonic Metamaterials and Invisibility Cloaks: The Making Of, Invited Plenary Keynote Talk, The 24th International Conference on Micro Electro Mechanical Systems (MEMS 2011), Cancun (Mexico), January 23-27, 2011. 31. M. Wegener, Photonic Metamaterials and Transformation Optics: Recent Progress, Spring-Meeting of the German Physical Society (DPG), Dresden (Germany), March 13-18, 2011. 32. M. Wegener, 3D Photonic Metamaterials and Transformation Optics, Invited Plenary Talk, International Conference on Nanophotonics (ICNP), Shanghai (China), May 22-26, 2011. 33. M. Wegener, International Symposium on Wave Propagation: From Electrons to Photonic Crystals and Metamaterials, Crete, Greece, June 8-11, 2011. 34. M. Wegener, Photonic Metamaterials: Optics Starts Walking on Two Feet, International Summer School on Nano-optics: plasmonics, photonic crystals, metamaterials, and sub-wavelength resolution, Advanced Study Institute, Ettore Majorana Centre, Erice (Italy), June 30 - July 15, 2011. 35. M. Wegener, Photonic Metamaterials and Transformation Optics, Invited Plenary Talk, International Conference on Fundamental Optical Processes in Semiconductors (FOPS 2011), Lake Junaluska, North Carolina (U.S.A.), August 1-5, 2011. 36. S. Linden, F.B.P. Niesler, and M. Wegener, Nonlinear spectroscopy on photonic metamaterials, Metamaterials: Fundamentals and Applications IV, SPIE 2011 Optics and Photonics Meeting, San Diego (U.S.A.), August 21-25, 2011. 37. T. Ergin, J. Fischer, J. Halimeh, N. Stenger, and M. Wegener, 3D invisibility cloaks at visible wavelengths, Metamaterials: Fundamentals and Applications IV, SPIE 2011 Optics and Photonics Meeting, San Diego (U.S.A.), August 21-25, 2011. 38. E. Ozbay, “Metamaterial Based Enhanced Transmission from Deep Subwavelength Apertures”, 3rd Mediterranean Conference on Nano-Photonics MediNano-3, Belgrade, Serbia, October 18-19, 2010. 39. E. Ozbay, “Metamaterial Based Enhanced Transmission from Deep Subwavelength Apertures,” 9th Photonics and Electromagnetic Crystals Conference (PECS-9), Granada, SPAIN, September 27-29 2010. 40. E. Ozbay, “The Magical World of Optical Metamaterials”, Metamaterials Congress 2010, Karlsruhe, GERMANY, September 13-16, 2010. 41. E. Ozbay, “Photonic Metamaterials: Science Meets Magic”, 6th Nanoscience and Nanotechnology Conference, Izmir, TURKEY, June 15-18, 2010. (Plenary Talk) PHOME 213390 Page 17

42. E. Ozbay, International Workshop on Photonic and Electromagnetic Crystal Structures, (PECS-IX), Granada, Spain, September 26-30, 2010. 43. E. Ozbay, “Metamaterial Based Enhanced Transmission from Deep Subwavelength Apertures,” The 3rd European Topical Meeting on Nanophotonics and Metamaterials, NanoMeta-2011, Seefeld, Tirol, Austria, January 3-6, 2011. 44. E. Ozbay, “The Magical World of Optical Metamaterials”, SPIE Photonic West 2011, San Francisco, USA, January 23-27, 2011. 45. E. Ozbay, “Science Meets Magic: Photonic Metamaterials”, SPIE Photonics Europe 2011, “Metamaterials” Prague, Czech Republic, April 18-21, 2011. 46. E. Ozbay, International Symposium on Wave Propagation: From Electrons to Photonic Crystals and Metamaterials, Crete, Greece, June 8-11, 2011. 47. J. B. Pendry, The 4th Yamada Symposium on. APSE 2010. Advanced Photons and Science Evolution 2010, Osaka Japan, June 14-18, 2010. 48. J. B. Pendry, Ninth European Summer Campus on the theme "Metamaterials," Strasbourg, France, June 27 - July 5, 2010. 49. J. B. Pendry, International Workshop on Photonic and Electromagnetic Crystal Structures, (PECS-IX), Granada, Spain, September 26-30, 2010.. 50. J. B. Pendry, New Approaches to Biochemical Sensing with Plasmonic Nanobiophotonics, Donostia International Physics Center in San Sebastian, Sept. 27- Oct. 1, 2010. 51. J. B. Pendry, Multistage modeling workshop, Erlangen, Germany, October 12, 2010. 52. J. B. Pendry, FOM conference, Veldhoven, The Netherlands, January 18-19, 2011. (Plenary Talk) 53. J. B. Pendry, NAVAIR Nano/Meta Materials Workshop for Naval Aviation Applications, Virginia, USA, February 2-3, 2011. 54. J. B. Pendry, Bringing together Nanoscience & Nanotechnology, Bilbao, Spain, April 11-14, 2011. (Plenary Talk) 55. J. B. Pendry, Recent Developments in Wave Physics of Complex Media, Cargese, Corsica, France, May 2-7, 2011. 56. J. B. Pendry, The European Future Technologies Conference and Exhibition 2011, Budapest, Hungary, May 4-6, 2011. (Plenary Talk) 57. J. B. Pendry, Annual international conference "Days of Diffraction" (Metamaterials Workshop), St. Petersburg, Russia, May 30 - June 3, 2011. 58. J. B. Pendry, International Symposium on Wave Propagation: From Electrons to Photonic Crystals and Metamaterials, Crete, Greece, June 8-11, 2011. 59. J. B. Pendry, 7th joint U.S./Australia/Canada/UK Workshop on Defense Applications of Signal Processing (DASP), , Coolum, Queensland, Australia, July 10-14, 2011. 60. J. B. Pendry, SPIE Optics and Photonics, San Diego, Ca, USA, August 21-25, 2011.

Talks/Seminars

M. Wegener

Martin Wegener, Photonische Metamaterialien, Physics Colloquium Universität Paderborn, June 24, 2010 Martin Wegener, Metamaterialien und Transformationsoptik, “Physik am Samstag“, Karlsruhe Institute of Technology (KIT), July 10, 2010 Martin Wegener, 3D Metamaterials and Transformation Optics, Annual Meeting of the International Max Planck Research School (IMPRS) Erlangen, Gößweinstein, Oktober 4-8, 2010 Martin Wegener, Metamaterialien und Transformationsoptik, Physics Colloquium Universität Osnabrück, November 11, 2010 Martin Wegener, Metamaterials and Transformation Optics, Optics Seminar University Twente (The Netherlands), November 25, 2010 PHOME 213390 Page 18

Martin Wegener, Metamaterialien und Transformationsoptik, j-DPG “Meet your Prof“, Karlsruhe, January 17, 2011 Martin Wegener, Photonic Metamaterials: Quo Vadis?, Final Colloquium of the DFG-Forschergruppe “Light Confinement and Control with Structured Dielectrics and Metals”, Bad Honnef, April 8, 2011 Martin Wegener, Das CFN, Visit of the ROTARY-Club “Karlsruhe Albtal“ at CFN, Karlsruhe, July 28, 2011

J. B. Pendry

14 September 2010 Lecture at UNESCO Niels Bohr Gold Medal ceremony, Copenhagen 23 September 2010 Resnick lecture Johns Hopkins university Baltimore 1 October 2010 Public lecture, San Sebastian, Spain 28 October 2010 Lecture to Oxford University physics students society 4 November 2010 Public lecture San Diego, USA 17 November 2010 Public lecture, Hong Kong 17 January 2011 Master class FOM meeting, Veldhoven, The Netherlands 1 March 2011, Solvay colloquium, Brussels, Belgium 11 March 2011, Colloquium, Helsinki, Finland 28 March 2011, Distinguished lecture, HKUST, Hong Kong 1 July 2011 Invited talk, A* Singapore Research Center, Singapore 5/6 July 2011 2 Lectures to the Harry Messel summer school, Sydney, Australia

M. Kafesaki

FORTH - Institute of Chemical Engineering and High Temperature Chemical Processes, Patras, Greece, November 2010.

C. M. Soukoulis

Solvay Colloquium, Brussels, Belgium, May 2011 PHOME 213390 Page 19

Deliverables and milestones tables

Deliverables (excluding the periodic and final reports)

TABLE 1. DELIVERABLES5

Del. Deliverable name WP Lead Disseminati Delivery Deliver Actual / Forecast Natu no. no. benefici on date from ed delivery date re ary level Annex I Yes/No (proj. month) D11 Assessment of the WP2- KIT-U R CO, PU 36 Yes Sept. 15, 2011 existence of IR and WP3 optical PMMs D12 Fabrication issues and WP2- KIT-U R CO, PU 36 Yes Sept. 15, 2011 optical characterization of WP3 bulk PMMs D13 Final plan for WP4 BILKENT R CO, PU 36 Yes Sept. 15, 2011 dissemination and use of foreground D14 Progress Report (3rd year) WP1- FORTH R CO, PU 36 Yes Sept. 15, 2011 WP4 D15 Report on awareness and WP4 IMPERIA R CO, PU 36 Yes Sept. 15, 2011 wider societal implication L D16 Conference sessions on WP4 FORTH R CO, PU 36 Yes Sept. 15, 2011 PMMs D17 Progress report (Final WP1- FORTH R CO, PU 36 Yes Sept. 15, 2011 report) WP5

Accomplishment of the deliverables D11: Assessment of the existence of IR and optical PMMs See the separate report on D11 (also in Appendix A) D12: Fabrication issues and optical characterization of bulk PMMs See the separate report on D12 (also in Appendix A) D13: Final plan for dissemination and use of foreground See the separate report on D13 D15: Report on awareness and wider societal implication See the separate report on D15 (also in Appendix A) D16: Conference sessions on PMMs See the separate report on D16 (also in Appendix A)

5 For Security Projects the template for the deliverables list in Annex A1 has to be used. PHOME 213390 Page 20

Project management

Dissemination

Below we mention some steps towards dissemination and use of the PHOME results. (A publication list and a list of conference presentations has been already reported in WP4 achievements).  We have created a web page where we have put our articles on PMMs. This page is linked to the CORDIS sites.  We present and we will continue to present the PHOME results through publications, colloquia, and participations to conferences and workshops.  We have organized sessions devoted to PMMs at international conferences (SPIE 2010, San Diego, USA, August 2010; Metamaterials Congress Conference, Karlsruhe, Germany September 2010; International Workshop on Photonic and Electromagnetic Crystal Structures, (PECS-IX), Granada, Spain, September 2010; Medi-Nano 3, Belgrade, Serbia, October 2010; 3nd International Workshop on Theoretical and Computational Nanophotonics (TaCoNa-Photonics), Bad Honnef, Germany, December 2010; The 3rd European Topical Meeting on Nanophotonics and Metamaterials, NanoMeta-2011, Seefeld, Tirol, Austria, January 2011; 41st Winter Colloquium on the Physics of Quantum Electronics (PQE), Snowbird (U.S.A.), January 2011; SPIE Photonics Europe 2011, “Metamaterials” Prague, Czech Republic, April 2011; International Conference on Materials for Advanced Technologies (ICMAT 2011), Singapore, June 2011; SPIE 2011, San Diego, USA, August 2011), where PHOME results will be advertised.  We have organized a conference on Photonic Metamaterials at Rethymnon, Crete, Greece, in June 2011. In this conference new results were presented and were discussed what are the challenges and the future of the photonic metamaterials. See the website http://cmp.physics.iastate.edu/wavepro/ and all the talks are posted in this site.  The experimental group of Karlsruhe is in discussion with industries about potential applications of PMMs as optical isolators. PHOME 213390 Page 21

Explanation of the use of the resources

TABLE 3.1 PERSONNEL, SUBCONTRACTING AND OTHER MAJOR DIRECT COST ITEMS FOR COORDINATOR (FORTH) FOR THE PERIOD Work Item description Amount Explanations Package 1, 2, 3 Personnel costs 130129,86€ Salary supplements for seven senior scientists, equivalent to 22.20 person months (~89694 €)

Partial salary coverage for three post-docs, equivalent to 15.32 person months (~31443€)

Salaries for two PhD students for 3,21 person months each (9000 €) 4 Travel expenses 41615,47 €  Participation of PHOME-related people to the final project conference (WavePro), Rethymnon, Crete, June 9-11, 2011 (3409 €).  Visit of C. Soukoulis in USA for collaboration (974 € + 1120 €+907€ +630 €).  Visit of C. Soukoulis in Athens, for collaboration with Demokritos Research center 3093  Participation of C. Soukoulis & M. Kafesaki in the 2nd PHOME review meeting in Karlsruhe (4349)  Visit of C. Soukoulis in Karlsruhe, for collaboration with Wegener’s group (838 €)  Visit of N. Katsarakis in Germany for collaboration (~1520 €)  Visit of M. Kafesaki in Belfast for collaboration with the Metamorphose Virtual Institute on Metamaterials (1285 €)  M. Kafesaki’s trip to US, for collaboration and participation in the SPIE conference on metamaterials (3583 €)  M. Kafesaki’s participation in the PIERS conference in Morocco (1772 €), in “Days of Diffraction” conference in St. Petersburg (1696 €), and in MISM conference in Moscow (2288 €)  Participation of three people in the ICMAT conference in Singapore (7734 €)  Host of visitors for discussion and collaborations (~4013€) 2, 3 Consumables 37389,42 € Photolithography masks, wafers and chemicals for lithography processes, computer accessories, small accessories for the THz characterization equipments, ready microwave metamaterial samples for testing the main ideas in the microwaves 1,3,4,5 Other 25604,17 € Costs for the organization of the WavePro conference (rooms, meals, stationary) (8874 €) Renting of room and equipment for the PHOME final review meeting (349 €) Payment of support and administration personnel (for WavePro conference and for general support) PHOME 213390 Page 22

(11571 €) Publication costs (1472 €) Maintenance and repairing of the FTIR equipment (1045 €) Stationary for the organization of the metamaterials schools (2252 €) Remaining direct costs TOTAL DIRECT COSTS6 234738,92 €

TABLE 3.1 PERSONNEL, SUBCONTRACTING AND OTHER MAJOR DIRECT COST ITEMS FOR BENEFICIARY 1 (IMPERIAL) FOR THE PERIOD Work Item description Amount Explanations Package wp1 Personnel costs €82,834.06 salary of the PDRAs working on this project - Subcontracting €0.00 - wp1/wp4 Major cost item Travel €2,656.69 travel by Dr Aubry, PDRA, to conferences relevant to the project wp1 Major cost item €3,341.25 computer software packages for simulation of Consumables. data - Remaining direct costs €0.00 TOTAL DIRECT COSTS7 €88,831.99

TABLE 3.1 PERSONNEL, SUBCONTRACTING AND OTHER MAJOR DIRECT COST ITEMS FOR BILKENT FOR THE PERIOD Work Item description Amount Explanations Package 1, 2, 3 Personnel costs 42.287,49 € Salaries of 2 postdoctoral researchers (for total 17 months) 2, 3, 4 Travel expenses 25.436,83 €  1 graduate student to Int School of Quantum Electronics, June 2010, Erice-Italy (1.710 €)  2 graduate students to 4th Int Congress on Advanced Electromagnetic Materials in Microwaves and Optics, September 2010, Karlsruhe-Germany (3.430 €)  E.Ozbay PHOME project meeting and 4th Int Congress on Advanced Electromagnetic Materials in Microwaves and Optics, September 2010, Karlsruhe-Germany (1.520 €)  1 graduate student to Lumerical FDTD Solutions Training, September 2010, London-England (940 €)  E.Ozbay July 2010 Project Review Meeting, Karlsruhe-Germany and October 2011 Project Final Review Meeting Barcelona-Spain (3.900 €)  2 graduate students to 17th EU PhD School on Matematerials, December 2010, Crete-Greece 6 Total direct costs have to be coherent with the directs costs claimed in Form C 7 Total direct costs have to be coherent with the directs costs claimed in Form C PHOME 213390 Page 23

(2.060 €)  E.Ozbay NanoMeta Conference, January 2011, Seefeld-Austria (1.700 €)  1 graduate student to MRS Meeting, April 2011, San Fransisco-USA (1.450 €)  1 graduate student to CLEO meeting, May 2011, Baltimore-USA (2.300 €)  E.Ozbay to WavePro Conference, June 2011, Crete-Greece (2.300 €)  2 graduate students to TDK UK Office training on Anechoic Chambers, July 2011, London-England (1.400 €)  2 graduate students to 18th EU PhD School on Matematerials, July 2011, Sienna-Italy (2.710 €) 1, 2, 3 Consumables 46.475,20 €  Consumables for the production of various chiral and composite metamaterial structures which are made of multiple layers of dielectric-metal composite structures. These consumables include PCB manufacturing costs, various substrates, antennas, FR4, Teflon and Rogers substrates, electromagnetic absorbers and the micromachining costs for these metamaterial based structures. (~25.200 €)  Consumables for micro-nanofabrication of various photonic metamaterial structures. These include photoresists, e-beam lithography consumables, micro-nanofabrication chemicals and substrates. (~14.800 €), Lumerical FTDT CAD tool for design of nanostructured metamaterials (~2.550 €), CST CAD tool for simulation of chiral metamaterials (~3.850 €) 1, 2, 3 Remaining direct costs TOTAL DIRECT COSTS8 114.199,52 €

TABLE 3.1 PERSONNEL, SUBCONTRACTING AND OTHER MAJOR DIRECT COST ITEMS FOR PARTNER KIT FOR THE PERIOD Work Item description Amount Explanations Package WP2 Personnel costs 97,646.78 Salary of 3 researchers for 28 months WP4 Travel expenses 3,689.02 Participation T. Ergin, J. Fischer Conference Cleo Quels, in San Jose, in May 2010 and conference in San Francisco, January 2011 Consumables Other Remaining direct costs TOTAL DIRECT COSTS9 101,335.80

8 Total direct costs have to be coherent with the directs costs claimed in Form C 9 Total direct costs have to be coherent with the directs costs claimed in Form C PHOME 213390 Page 24

Appendices

Appendix A: Deliverables

In the next pages the following deliverables have been appended:

Deliverable 11: Assessment of the existence of IR and optical Photonic Metamaterials

Deliverable 12: Report on fabrication issues and optical characterization of bulk Photonic Metamaterials

(Deliverable 13: Final plan for dissemination and use of foreground – it will be submitted as a separate document)

Deliverable 15: Report on awareness and wider societal implications on metamaterials

Deliverable 16: Conference sessions on Photonic Metamaterials PHOME 213390 Page 25

Deliverable 11: Assessment of the existence of IR and optical Photonic Metamaterials

Before the beginning of the PHOME project, photonic metamaterials were not actually “materials” but they were rather planar films composed of planar metamaterial building blocks. As one makes the step from single functional layers to three-dimensional structures, the issue of losses becomes more prominent. Suppose that the transmittance of a single metamaterial layer is as large as 90%. For hundred layers, the resulting transmittance would be as low as (0.9)100=2.7×10-5 – essentially a completely opaque hence practically useless structure. Thus, making photonic metamaterials more bulky on the one hand and making them less lossy on the other hand are two closely related aspects. Regarding both aspects, the PHOME project has made tremendous progress. The KIT and FORTH partners have recently jointly published two corresponding reviews on this matter, one brief perspectives article in Science in December 2010 [D11:1] and one comprehensive review in Nature Photonics that appeared in August 2011 [D11:2]. Another more popular- oriented review has already appeared in Physics Today in October 2010 [D11:3].

Figure D11.1: Overview of three-dimensional photonic metamaterials. Taken from Ref.[D11:2]. Many of these structures have been realized within PHOME, which has taken a leading role within Europe. Other structures like the ones in (d)-(g) have been realized by groups in North America.

Figure D11.1 summarizes different three-dimensional architectures taken from one of these reviews [D11:2]. Stacked double-fishnet negative-index metamaterials operating at telecom frequencies along the lines of (a) had already been realized by PHOME partners before the beginning of PHOME. More flexibility arises upon stacking different independent functional layers made by electron-beam lithography like shown in (b). A variety of corresponding chiral structures were previously made and jointly published by the KIT and FORTH partners as reported in PHOME deliverable D10. These results could recently be further improved in a joint effort between KIT and FORTH by going from twisted crosses [D11:4] towards twisted split-ring resonator architectures [D11:5]. This structure is in fact closely similar to the one PHOME 213390 Page 26 shown Fig.D11.1(c). In D10, we also reported on another approach based on three- dimensional direct-laser-writing (DLW) optical lithography and gold electroplating shown in (c). The corresponding gold-helix metamaterial acts as a compact broadband circular polarizer and represents an early real-world application of the far-reaching ideas of photonic metamaterials. In D12 we will report on our corresponding PHOME progress with respect to further moving the operating frequencies of three-dimensional metamaterial structures from the infrared towards the visible spectral range by introducing stimulated-emission-depletion (STED) DLW optical lithography. The KIT partner has also continued along the lines of the circular polarizer, aiming at systematically further improving its suppression ratio as well as its bandwidth. The latter can, e.g., by improved by chirping the diameter of the gold helix from the substrate side towards the top. It is known from antenna theory that the resonance wavelength is basically proportional to the helix diameter. Thus, adiabatically tapering the helix diameter enables increasing the bandwidth. However, careful numerical studies were required to find a compromise between sufficiently slow tapering and reasonable overall helix length (unpublished). Corresponding metamaterial structures are presently being fabricated and characterized by KIT. In addition, the circular-polarizer suppression ratio can be increased by more than an order of magnitude by going from a single helix in one metamaterial unit cell to three interwoven helices (compare DNA). Here, the idea is to eliminate the remaining linear birefringence that results from the axis defined by the end of the metal wire and the center of the helix. However, realizing corresponding structures requires more advanced STED-DLW optical lithography (see D12). Such advance might also allow realizing the cubic-symmetry negative-index metamaterial architecture proposed by the FORTH partner and shown in Fig.D11.1 (h). Regarding metamaterial losses, the collaboration between KIT and FORTH has investigated further the microscopic origin of losses in magnetic metamaterials composed of split-ring resonators operating at telecom frequencies [D11:6]. By detailed experiments and calculations varying both the metamaterial lattice constant as well as the angle of incidence in oblique- angle transmittance, it was found that long-range retardation effects can influence the resonance damping by as much as a factor of three. This means that a considerable fraction of the losses can be eliminated by design. It also means that the metamaterial acts like one entity. This aspect avoids undesired breaking up into domains upon introducing optical gain. Metamaterial losses can also be reduced by as much as 30% by post-processing of structures made via electron-beam lithography using restructuring by electrochemical means [D11:7]. This work has built upon our earlier PHOME work regarding electromodulation of photonic metamaterials [D11:7]. Ultimately, however, optical gain needs to be introduced if loss-free operation should be required. The PHOME approach has been from the start to employ semiconductor optical gain by bringing a single quantum well in close proximity to the meta-atoms, e.g., to split-ring resonators. Meanwhile the joint KIT and FORTH work that we reported on in D8 has appeared [D11:9]. More recently, we could demonstrate in direct experiments that the coupling between quantum well and split-ring resonators decays on a scale of a mere ten nanometers (submitted). These results largely benefited from PHOME work on spatially resolving the electromagnetic fields near meta-atoms by either electron-energy-loss spectroscopy [D11:10] or phase-sensitive optical near-field microscopy/spectroscopy [D11:11]. Another interesting avenue is to turn the often undesired metamaterial losses to our advantage. Indeed, several groups have previously suggested metamaterial perfect absorbers, PHOME 213390 Page 27 however, without turning the heat generated via optical absorption into an actually useful electrical signal. To this end, the KIT partner has successfully realized a first integrated metamaterial bolometer depicted in Fig.D11.2 (unpublished).

Figure D11.2: Electron micrographs (different magnifications increasing from top left to bottom right) of an operational integrated metamaterial bolometer structure fabricated by electron-beam lithography onto a free- standing 30-nm thin SiN membrane on a silicon substrate (unpublished).

Upon resonant absorption of light in the split-ring-resonator like objects (bottom right in Fig.D11.2), the connected gold meander is heated, hence changing its Ohmic resistance. This resistance change is measured in four-point geometry. The conceptual advantage compared to usual bolometers is that the metamaterial allows for integrating a spectral filter as well as a polarization filter. Both aspects reduce thermal noise. Along these lines, average powers below one µW at around 1.5-µm wavelength could be detected by the KIT partner at room temperature. This design can easily be scaled to other operation wavelengths. In this fashion, also cameras with built-in spectrometers may become possible. Notably, this bolometer is entirely metal-based – the SiN membrane merely serves for mechanical stability. Another interesting application of metamaterials lies in frequency conversion, e.g., in second- harmonic generation. Building on our previous PHOME work, the KIT partner recently performed second-harmonic-generation spectroscopy on split-ring-resonator arrays for the first time [D11:12]. These experiments might prove helpful in identifying the microscopic origin of the metamaterial nonlinearities – which is still not well understood theoretically at present. PHOME 213390 Page 28

References D11 [D11:1] C.M. Soukoulis and M. Wegener, Optical Metamaterials: More Bulky and Less Lossy, Science 330, 1633 (2010) [D11:2] C.M. Soukoulis and M. Wegener, Past achievements and future challenges in the development of three-dimensional photonic metamaterials, Nature Photon., in press (2011) [D11:3] M. Wegener and S. Linden, Shaping Optical Space with Metamaterials, Physics Today 63, 32 (2010) [D11:4] M.J. Huttunen, G. Bautista, M. Decker, S. Linden, M. Wegener, and M. Kauranen, Nonlinear chiral imaging of subwavelength-sized twisted-cross gold nanodimers, Opt. Mater. Express 1, 46 (2011) [D11:5] M. Decker, R. Zhao, C.M. Soukoulis, S. Linden, and M. Wegener, Twisted split- ring-resonator photonic metamaterial with huge optical activity, Opt. Lett. 35, 1593 (2010) [D11:6] M. Decker, N. Feth, C.M. Soukoulis, S. Linden, and M. Wegener, Retarded long- range interaction in split-ring-resonator square arrays, Phys. Rev. B 84, 085416 (2011) [D11:7] M. Ruther, L. Shao, S. Linden, J. Weissmüller, and M. Wegener, Electrochemical Restructuring of Plasmonic Metamaterials, Appl. Phys. Lett. 98, 013112 (2011) [D11:8] L. Shao, M. Ruther, S. Linden, S. Essig, K. Busch, J. Weissmüller, and M. Wegener, Electrochemical Modulation of Photonic Metamaterials, Adv. Mater. 22, 5173 (2010) [D11:9] N. Meinzer, M. Ruther, S. Linden, C.M. Soukoulis, G. Khitrova, J. Hendrickson, J.D. Olitzky, H.M. Gibbs, and M. Wegener, Arrays of Ag split-ring resonators coupled to InGaAs single-quantum-well gain, Opt. Express 18, 24140 (2010) [D11:10] G. Boudarham, N. Feth, V. Myroshnychenko, S. Linden, O. Stephan, C. Colliex, J. Garcia de Abajo, M. Wegener, and M. Kociak, Spectral Imaging of Individual Split-Ring Resonators, Phys. Rev. Lett. 105, 255501 (2010) [D11:11] M. Burresi, D. Diessel, D. van Osten, S. Linden, M. Wegener, and L. Kuipers, Phase-sensitive near-field optical microscopy on negative-index metamaterials, Nano Lett. 10, 2480 (2010) [D11:12] F.B.P. Niesler, N. Feth, S. Linden, and M. Wegener, Second-harmonic optical spectroscopy on split-ring-resonator arrays, Opt. Lett. 36, 1533 (2011) PHOME 213390 Page 29

Deliverable 12: Report on fabrication issues and optical characterization of bulk Photonic Metamaterials

The strategy of PHOME towards achieving truly three-dimensional (and bulk) photonic metamaterials has been to follow two fabrication routes in parallel, namely, planar electron- beam lithography plus stacking of several layers on the one hand (KIT and Bilkent) and inherently three-dimensional direct-laser-writing (DLW) optical lithography on the other hand (KIT). The previous status has been reported on in D10, which shall not be repeated here. Meanwhile it has become clear that the DLW approach – which seemed like the more risky one at the start – is actually advantageous in terms of fabrication complex structures within reasonable time. However, a major drawback of DLW optical lithography has been its limited spatial resolution, which has not been anywhere near that of state-of-the-art electron-beam lithography. This aspect has limited further progress by the FORTH and KIT partners regarding three-dimensional chiral metamaterials as well as further progress with respect to three-dimensional transformation-optics architectures (e.g., invisibility cloaks) that the collaboration between KIT and Imperial introduced in a publication in Science magazine in early 2010. This contrasted the theoretical progress made in PHOME [D12:1] [D12:2] [D12:3]. Thus, the KIT partner has put tremendous effort on systematically improving the spatial resolution of DLW optical lithography in all three dimensions by combining [D12:5] [D12:6] it with the concept of stimulated-emission-depletion (STED) known from fluorescence microscopy. The underlying idea is illustrated in Fig.D12.1.

Figure D12.1: (a) Scheme of stimulated-emission-depletion (STED) direct-laser-writing (LW) optical lithography. A red laser focus exposes the photoresist, while a green laser depletes (or de-excites or “erases”) from all sides using a bottle beam. (b) Foci measured by scanning a gold bead through the focus in three dimensions. Taken from Ref.[D12:5].

Using this approach, we were able to miniaturize our 2010 result by more than a factor of two in all three spatial directions. This step has brought the operation frequency from the infrared all the way to the visible part of the electromagnetic spectrum. In particular, optical microscopy revealed excellent cloaking in three dimensions and for any polarization of light at 700-nm wavelength [D12:4]. In this publication, we also systematically studied the wavelength dependence. Only at wavelengths below 600 nm does the light field “feel” the PHOME 213390 Page 30 underlying periodicity of the metamaterial. Hence, deviations from the effective-medium approximation occur. Comparison of the experiments by the KIT partner with ray-tracing modelling along the lines of Ref.[D12:1] revealed only minor imperfections with respect to the carpet-cloak design introduced by the Imperial partner in 2008.

Figure D12.2: Scheme of the imaging Michelson interferometer allowing for directly measuring the phase front reconstruction by a carpet invisibility cloak. Taken from Ref.[D12:8].

In a broad sense, invisibility cloaking based on photonic metamaterials can be viewed as a particularly demanding example of aberration corrections, which are of interest in many optical systems. Here, however, not only correction of the light amplitude but also of the phase of the light wave is mandatory. While the two are connected by the Maxwell equations, not a single far-field optical experiment had previously actually shown that such invisibility cloaks also properly reconstruct the phase of the wave. To test this aspect, the KIT partner has built a dedicated imaging interferometer for detailed optical characterization (see Fig.D12.2). Using this refined characterization set-up, the phase images shown in Fig.D12.3 have been obtained. Obviously, the bump at the top (compare T. Ergin et al., Science 328, 337 (2010)) shows up as a phase hill for the reference. The phase distortion almost completely vanishes for the case of the cloaking structure shown at the bottom. The same three-dimensional STED-DLW lithography shall also allow for further miniaturizing and improving our previously introduced gold-helix photonic metamaterials that act as broadband circular polarizers. The corresponding status is reported in D11. However, STED-DLW optical lithography is presently restricted to negative-tone photoresist, whereas electroplating for gold helices required a positive-tone photoresist. Thus, an additional inversion step is necessary. We are pursuing atomic-layer deposition of a sacrificial dielectric before electroplating with gold. Encouraging progress has recently been made by the KIT partner. The same technology can also be applied to fabricate the corrugated-wire metamaterials theoretically introduced by the FORTH partner to achieve bulk three- dimensional negative-index metamaterials with improved angular dependence. Another promising route is to replace the traditional metals (e.g., gold or silver) by very highly doped semiconductors. This was, e.g., recently suggested by Alexandra Boltasseva and Harry Atwater (Science 331, 290 (2011)) for planar metamaterial structures. In PHOME, the KIT partner has successfully fabricated [D12:7] three-dimensional architectures based on Al- doped ZnO grown by atomic-layer deposition. Plasma frequencies up to visible frequencies PHOME 213390 Page 31 have been achieved at reasonably small losses [D12:7]. Thus, this approach appears to be very attractive for three-dimensional infrared metamaterials and transformation-optics architectures.

Figure D12.3: Measured phase images (compare Fig.D12.2) on carpet-cloak photonic metamaterial structures made by STED-DLW optical lithography and measured at 700-nm wavelength of light. Taken from Ref.[D12:8].

The other novel path in facing losses is based on a combination of electromagnetically- induced transparency (EIT) with non-linearity and gain components. EIT in metamaterials is based on two elements—the active and the dark; one of the elements, according to our proposed design, incorporates the gain component and transfers the energy non-linearly to the other element. Under certain conditions, the spectral response of such a coupled structure can be significantly different from the mere superposition of the two independent resonances. Recently, we have fabricated two EIT structures [D12:9, D12:10] that showed low absorption and slow light velocity. Figure D12.4 shows the photograph of the sample and the schematic representation of our structure [D12:9].

Fig. D12.4. (a) Photograph of the sample. (b) Schematic Fig. D12.5. All spectra exhibit the typical features of EIT- with representation of our structure. Ref. [D12:9]. low absorption inside a broader resonance. Ref. [D12:9].

Therefore, the absorption spectrum develops a very narrow transmission window in the broader Lorentzian-like absorption peak associated with the transition to the excited state (see Fig. D12.4). Slow Light: Another application of the EIT is to slow the light by a large factor. At the resonance frequency, the anomalous dispersion profile, normally observed for a two-level PHOME 213390 Page 32 resonance, is transformed into an extremely steep normal dispersion. This may slow down light pulses by many orders of magnitude [D12:10]. Most of the EIT experimental work has not seen a strong absorption dip, and the reduction of the speed of light is very small—a factor of five to ten. So there is a strong need to experimentally demonstrate that metamaterials can reduce the speed of light dramatically. We have collaborated with Prof. Steven Anlage’s group, from the Univ. of Maryland, which has expertise in fabricating superconducting wires. We have fabricated [D12:10] these EIT structures with metals and superconductors, to verify that the experimental results will agree with our numerical simulations and reduce the speed of light by a factor of 500. Therefore, we will have a strong reduction in the speed of light and these new samples will be useful to construct light-slowing devices. In addition, by manipulation of the superconducting properties of the dark resonators through temperature or magnetic field, the EIT effects are tunable to an unprecedented extent [D12:10].

References D12

[D12:1] T. Ergin, J.C. Halimeh, N. Stenger, and M. Wegener, Optical microscopy of 3D carpet cloaks: ray-tracing simulations, Opt. Express 18, 20535 (2010) [D12:2] R. Schmied, J.C. Halimeh, and M. Wegener, Conformal carpet and grating cloaks, Opt. Express 18, 24361 (2010) [D12:3] J.C. Halimeh, R. Schmied, and M. Wegener, Newtonian photorealistic ray tracing of grating cloaks and correlation-function-based cloaking-quality assessment, Opt. Express 19, 6078 (2011) [D12:4] J. Fischer, T. Ergin, and M. Wegener, Three-dimensional polarization-independent visible-frequency carpet invisibility cloak, Opt. Lett. 36, 2059 (2011) [D12:5] J. Fischer and M. Wegener, Three-dimensional direct laser writing inspired by stimulated-emission-depletion microscopy, Opt. Mater. Express 1, 614 (2011) [D12:6] T.J.A. Wolf, J. Fischer, M. Wegener, and A.-N. Unterreiner, Pump-probe spectroscopy on photoinitiators for stimulated-emission-depletion optical lithography, Opt. Lett., in press (2011) [D12:7] A. Frölich and M. Wegener, Spectroscopic characterization of highly doped ZnO by atomic-layer deposition for three-dimensional infrared metamaterials, Opt. Mater. Express, in press (2011) [D12:8] T. Ergin, J. Fischer, and M. Wegener, Optical phase cloaking of 700-nm light waves in the far field by a three-dimensional carpet cloak, submitted (2011); arXiv:1107.4288v1

[D12:9] R. Zhao, Lei Zhang, J. Zhou, Th. Koschny and C. M. Soukoulis, “Conjugated gammadion chiral metamaterials with optical activity and negative refractive index,” Phys. Rev B 83, 035105 (2011).

[D12:10] C. Kurter, P. Tassin, Lei Zhang, Th. Koschny, A. P. Zhuravel, A. V. Ustinov, S. M. Anlage and C. M. Soukoulis, “Classical analogue of Electromagnetic Induced Transparency with a metal/superconductor hybrid metamaterial,” Phys. Rev. Lett. 107, 043901 (2011). PHOME 213390 Page 33 PHOME 213390 Page 34

Deliverable 15: Report on awareness and wider societal implications on metamaterials

Optics in particular and electromagnetic radiation in general pervades every aspect of our lives. We only have to think of mobile phones, optical fibers for telecoms, MRI, optical microscopy, GPS, satellite communications, laser surgery, THz imaging for security, keyhole surgery enabled by endoscopes: the list is endless. Yet whenever an application comes to be realized we have to ask what materials will be used to manufacture the device and therein lays a problem. Electromagnetic theory allows a wide range of material properties and indeed requires many of these properties to achieve some of the more exotic applications. However nature has not been so generous and many useful properties are missing from the list of naturally available materials. So it is that metamaterials have come to be such an important and well-studied field. The concept is very simple: a material’s properties can be changed not only by altering the chemistry of its constituents but also by altering its microscopy structure, structure on a scale much less than the wavelength. A good example with which we are familiar is silver. As a flat highly polished surface silver makes an excellent mirror. On the other hand very finely divided silver nanoparticles that are to be found in a black and white photographic negative absorb light and are black in appearance. This powerful concept can generate astonishing material properties such as negative refraction and chirality far more strong than found in any naturally occurring material. The concept is relatively simple to apply for RF applications because the wavelength is relatively large and the sub wavelength structures of the metamaterial are of easily manufactured dimensions. Greater challenges appear when pushing the concept into the THz, IR and visible regions of the spectrum where, arguable the greater societal rewards are to be found. In this respect the Karlsruhe partner is perfecting the technology for optical metamaterials where the length scales of the structures are on the nanoscale. At the same time the FORTH partner using computational techniques has been probing other limits to visible frequency metamaterials. Even metamaterials have to be manufactured from naturally occurring substances and ultimately their properties will limit what can be achieved with metamaterials. In particular the responsiveness of electrons at higher frequencies becomes sluggish leading to absorption of incident radiation. Conquering these limitations with clever designs was required to extend the applicability of metamaterials.

Not only do scientists find the new concepts stimulating, but also they have such a simple but powerful idea behind them that a popular audience can easily grasp their significance. Several of the team has spent much time giving popular lectures to general audiences, including outreaching to schoolchildren. Over the course of the project of the order of 100 lectures will have been delivered by members of the team provoking interest in and appreciated of not just our particular area of research but of the social significance of science in general.

An exciting field such as metamaterials often leads to strong debate. This is of course the stuff of scientific progress: identifying challenges and debating the way forward until an agreed solution is found. These debates often attract the attention of the press both for the scientific issues themselves, of course, but also for the interplay of personalities. This exposure to the general public of scientists as people who sometimes collaborate, sometimes disagree, sometimes quarrel, adds a human dimension to the public perception of science that is all to often missing from the reporting of science. Members of the PHOME team have been prominent in the many debates that have taken place and been reported. For example the work PHOME 213390 Page 35 of the Karlsruhe group was reported in The New York Times: “Strides in Materials, but No Invisibility Cloak”, November 9th, 2010 and in The International Herald Tribune: “Dreaming Up Uses for a Giant Invisibility Machine”, November 29th, 2010. The work of the FORTH group was reported in many Greek newspapers, like Kathimerini, Eleftherotypia, Enthos and Patris.

In another recent instance, Pendry, Imperial College, delivered a series of lectures in Sydney Australia to the Harry Messel School. Exceptionally bright school children from all over the world are invited to Sydney to participate in 2 weeks of science. During their stay they are presented with a book containing write ups of the lectures that they hear, an enduring memento of their experiences. The book of lectures for the 36th Professor Harry Messel International School 2011, “Light and Matter”, is available from their web site at: http://www.physics.usyd.edu.au/foundation.old/index_iss.html PHOME 213390 Page 36

Deliverable 16: Conference sessions on Photonic Metamaterials

In this Deliverable we list the conferences and schools where sessions on photonic metamaterials have been organized (or co-organized) by members of the PHOME project, or where members of PHOME participated in the organizing and program committee.

Conferences chaired or co-chaired by PHOME people with sessions on photonic metamaterials

1. XXIV Panhellenic Conference of Solid State Physics and Materials Science, Heraklion, Crete, Greece, September 2008 2. 1st Mediterranean conference on Nanophotonics (Medi-Nano 1), Istanbul, Turkey, October 2008 3. OSA Topical Meeting Plasmonics and Metamaterials (META), Rochester ,USA, Oct 2008 4. Heraeus Workshop Periodic Nanostructures for Photonics, Bad Honnef, Germany, 2008 5. International conference on Electrical, Transport and Optical Properties of Inhomogeneous Media (ETOPIM 8), Rethymnon, Crete, Greece, June 2009 6. 2nd Mediterranean conference on Nanophotonics (Medi-Nano 2), Athens, Greece, October 2009 7. The 2nd European Topical Meeting on Nanophotonics and Metamaterials, (NanoMeta), Seefeld, Tirol, Austria, January 2009 8. Metamaterials 2010 Conference, Karlsruhe, Germany, September 2010 9. OSA Photonic Metamaterials and Plasmonics (META), Tuscon, USA, June 2010 10. SPIE Photonics Europe, Brussels, April 2010 11. Wave Propagation: from electrons to photonic crystals and metamaterials (WavePro), Rethymnon, Crete, Greece, June 2011 (conference organized and supported by PHOME), http://cmp.physics.iastate.edu/wavepro/

Schools related to photonic metamaterials organized by PHOME people

1. School on Fabrication and Optical Properties of Nanostructured Metamaterials, Rethymnon, Crete, Greece (June 12-13, 2009). 2. European School on Experimental Characterization of Electromagnetic Metamaterials, Heraklion (FORTH), Crete, Greece (December 13-17, 2010) 3. Summer School Bringing Gain to Metamaterials, Karlsruhe, Germany (2010) 4. CFN summer school Nano-Photonics, Bad Herrenalb, Germany, 2010

Conferences where PHOME people participated in the organizing committee and the program committee or organized sessions on photonic metamaterials

1. The first International Workshop on Theoretical and Computational Nanophotonics (TaCoNa-Photonics), Bad Honnef, December 2008 PHOME 213390 Page 37

2. International Conference on “Quantum Electronics and Laser Science (QELS)”, San Francisco, USA, 2008 3. SPIE Europe, Photonics Europe 2008, Strasbourg, France, 2008 4. Photonic and Electromagnetic Crystal Structures (PECS), Sydney, Australia, April 2009 5. SPIE Optics and Photonics, San Diego, USA, August 2009 6. 2nd International Workshop on Theoretical and Computational Nanophotonics (TaCoNa- Photonics), Bad Honnef, Germany, December 2009 7. MRS Fall Meeting, Boston, USA, December 2009 8. 40th Winter Colloquium of Quantum Electronics, Snowbird, USA, January 2010 9. META’10, Cairo, Egypt, February 2010 10. International Quantum Electronics Conference (IQEC), Baltimore, USA, 2010 11. SPIE Optics and Optoelectronics, Prague, Czech Republic, 2010 12. SPIE 2010, San Diego, USA, August 2010 13. Photonic and Electromagnetic Crystal Structures, (PECS-IX), Granada, Spain, September 2010 14. 3rd Mediterranean conference on Nanophotonics (Medi-Nano 3), Belgrade, Serbia, October 2010 15. 3nd International Workshop on Theoretical and Computational Nanophotonics (TaCoNa- Photonics), Bad Honnef, Germany, December 2010 16. The 3rd European Topical Meeting on Nanophotonics and Metamaterials, NanoMeta- 2011, Seefeld, Tirol, Austria, January 2011 17. 41st Winter Colloquium on the Physics of Quantum Electronics (PQE), Snowbird, USA, January 2011 18. SPIE Photonics Europe 2011, Prague, Czech Republic, April 2011 19. International Conference on Materials for Advanced Technologies (ICMAT 2011), Singapore, June 2011 20. CLEO: Science (formerly QELS), Baltimore, USA, 2011 21. SPIE Optics and Photonics 2011, San Diego, USA, August 2011