DOCSLIB.ORG

Table-Top Tunable Narrow-Band Xuv Sources

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Table-Top Tunable Narrow-Band Xuv Sources Table-top tunable narrow-band extreme-ultraviolet sources: from low to high-order optical harmonic generation VRIJE UNIVERSITEIT Table-top tunable narrow-band extreme-ultraviolet sources: from low to high-order optical harmonic generation ACADEMISCH PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Vrije Universiteit Amsterdam, op gezag van de rector magnificus prof.dr. T. Sminia, in het openbaar te verdedigen ten overstaan van de promotiecommissie van de faculteit der Exacte Wetenschappen op donderdag 1 juli 2004 om 15.45 uur in het auditorium van de universiteit De Boelelaan 1105 door Fernando Brandi geboren te Pisa, Italie¨ promotor: prof.dr. W.M.G. Ubachs A Roberta, per la pazienza avuta. Contents 1 Introduction 1 1.1 Optical harmonic generation .......................... 1 1.2 Low-order harmonic generation ........................ 3 1.2.1 Perturbative solution .......................... 3 1.2.2 VUV sources for high-resolution spectroscopy ........... 7 1.3 Photoionization mechanisms ......................... 11 1.4 High-order harmonic generation ....................... 13 1.4.1 The semiclassical model ........................ 13 1.4.2 Propagation effects ........................... 14 1.4.3 Generation of tunable coherent XUV radiation ........... 18 I LHG applied to high-resolution VUV spectroscopy 23 2 High-resolution photoionization spectroscopy of xenon 25 2.1 Introduction ................................... 25 2.2 Experiment .................................... 26 2.3 Results and Discussion ............................. 27 2.3.1 Hyperfine Splitting ........................... 27 2.3.2 Isotope Shift ............................... 29 2.3.3 Absolute Calibration .......................... 33 2.4 Conclusions ................................... 35 3 High-resolution photoionization spectroscopy of krypton 37 3.1 Introduction ................................... 37 3.2 Experimental setup and procedure ...................... 39 3.2.1 1VUV+1UV photoionization spectroscopy ............. 39 3.2.2 2UV+1UV photoionization spectroscopy .............. 40 3.3 Experimental results and discussion ..................... 41 3.3.1 Isotope Shift ............................... 41 3.3.2 Absolute frequency calibration .................... 45 3.3.3 ac Stark effect .............................. 47 3.3.4 Consequences for narrow-band XUV/VUV generation ...... 49 3.4 Conclusions ................................... 51 i Contents 3.5 Appendix: new determination of the ionization energy of krypton .... 51 II A novel setup for narrow-band HHG 53 4 Laser system 55 4.1 Introduction ................................... 55 4.2 Laser system ................................... 57 4.2.1 cw-seeder ................................ 57 4.2.2 Pump and compressor ......................... 58 4.2.3 Pulsed-dye-amplifier .......................... 58 4.2.4 Ti:Sapphire amplifier .......................... 61 4.3 Characterization of the laser system ..................... 62 4.3.1 Temporal and frequency characteristics ............... 62 4.3.2 Spatial beam quality .......................... 64 5 Narrow-band high-order harmonic generation 67 5.1 Introduction ................................... 67 5.2 Experiment and results ............................. 69 5.3 Discussion .................................... 71 5.3.1 Absolute frequency of the harmonics ................ 71 5.3.2 Bandwidths of the harmonics ..................... 71 5.3.3 Tunability of the harmonics ...................... 72 5.4 Conclusions ................................... 74 5.5 Appendix: determination of the number of XUV photons ......... 74 6 High-resolution investigation of frequency chirp in HHG 79 6.1 Introduction ................................... 79 6.2 Experimental setup and procedure ...................... 81 6.3 Results and interpretation ........................... 84 6.4 Discussion .................................... 89 6.5 Conclusions and outlook ............................ 91 6.6 Appendix: measurement of the frequency shift in the amplifier chain .. 92 6.6.1 Experimental setup and technique .................. 92 6.6.2 Misalignment effect .......................... 94 Samenvatting 97 Summary 99 ii Contents Riassunto 101 Acknowledgments 103 Publications 105 Bibliography 107 iii Contents iv Chapter 1 Introduction The process of harmonic generation with laser radiation and its use for high-resolution spectroscopy are presented. In specific, low and high-order harmonic generation in gaseous media as a source of coherent radiation in the vacuum-ultraviolet (VUV, 200- 100 nm) and extreme-ultraviolet (XUV, 100-10 nm) are discussed. A description of photoionization mechanisms in intense laser pulses is also given. Spectroscopic appli- cation of low-order harmonic generation and wave-mixing, as well as recent progress and future prospects in the use of high-order harmonic generation for the development of a continuously tunable narrow-band table-top XUV source are presented. 1.1 Optical harmonic generation Optical harmonic generation (OHG) is the prototype process of nonlinear optics, the study of the interaction between intense optical radiation and matter. In the physi- cal process of OHG an intense light field interacting with matter produces radiation at spectral components, called harmonics, with frequencies at integer multiples of the fundamental frequency. Experimental investigations of nonlinear optics have become possible only with the invention of the laser [1] which made available sufficiently in- tense light beams; the first nonlinear optical phenomenon observed has been the gen- eration of second harmonics in a crystal in 1961 [2]. Low-order harmonic generation (LHG), q ≤ 5, is a nonlinear optical process that can be fully explained with a perturbative solution of Maxwell’s equations. At light intensities needed to trigger LHG process, typically in the range 109 − 1012 W/cm2, the optical response of a medium is determined by the dipole moment per unit vol- ume, or polarization, which can be expressed as a power series in the electric field associated with an intense light beam. Harmonic radiation is produced with an effi- ciency that rapidly decreases with the harmonic order, as is schematically shown in Figure 1.1(a). Note that in an isotropic medium, e.g., gases, for symmetry reasons only odd harmonics are produced. In most practical cases LHG is used to produce coherent electromagnetic radiation at those short wavelengths where laser radiation is not available, at least not in tunable or narrow-band form. A key prerequisite for efficient frequency conversion is the availability of a nonlinear material transparent at both the fundamental and the harmonic frequency. Crystals are routinely used to up-convert near-infrared and visible laser radiation, generating radiation down to the deep ultraviolet, with efficiencies up to 50%. However, generation of short wavelength 1 Chapter 1 (a) (b) Cut-off = E + 3Up Fast decrease Plateau Only odd harmonics Harmonic yield, arb. units Harmonic yield, arb. units 1 3 5 7 9 Harmonic order Harmonic order Figure 1.1. Schematic presentation of the typical spectra from low (a) and high (b) order har- monic generation in gases. harmonics in crystals is not possible due to the lack of transparent materials below 200 nm. Thus, the production of vacuum-ultraviolet (200-100 nm) and extreme-ultraviolet (100-10 nm) harmonic radiation is feasible only in gaseous media, but at much lower efficiency, typically 10−4 − 10−7. The development in the last two decades of high-power ps and fs pulsed lasers, has brought the discovery of new features in optical harmonic generation. Notably, it has been found that at very high field intensity, I ≥ 1013 W/cm2, a plateau in the harmonic generation efficiency is reached, as is schematically shown in Figure 1.1(b). At such high intensities the atoms are ionized by the laser pulse and perturbation theory is no longer valid. Harmonic generation in the high field regime can be understood in terms of a semiclassical approach, the so-called three-step model: first the atom is ionized by the intense laser field, then the free electron accelerates in the laser field and finally it recombines with the parent ion. This model predicts a cutoff at a photon energy of about E + 3Up, where E is the ionization energy of the atom and Up is the ponderomotive energy of an electron in the intense laser field. This nonlinear optical process, called high-order harmonic generation (HHG), has an efficiency that is orders of magnitude lower then LHG, typically 10−8 − 10−11 [3]. However, efficiencies on the order of 10−6 − 10−7 can be obtained if special interaction geometries are used, e.g., gas filled hollow fibers [4] or valves with a slit opening [5]. Nowadays, HHG has become a leading research field in nonlinear optics as a way to produce coherent soft- X-rays and attosecond pulses. Generation of radiation in the water window [6] and of sub-femtosecond pulses [7] has already been demonstrated. In the following Sections OHG in gases for the generation of tunable narrow-band XUV coherent radiation is described. In Section 1.2 the basic perturbation theory of LHG in gases is presented and applications of the generated VUV radiation in high- resolution spectroscopy is discussed. In Section 1.3 the onset of the photoionization mechanism of an atom in an intense laser field is presented. Finally, in Section 1.4 a semi-classical model for HHG in gases is presented, and the use of high-order harmon- ics in spectroscopic applications discussed. 2 Introduction 1.2 Low-order
Load more

Recommended publications
  • Single-Pass Laser Frequency Conversion to 780.2 Nm and 852.3 Nm Based on Ppmgo:LN Bulk Crystals and Diode-Laser-Seeded Fiber Amplifiers
    applied sciences Article Single-Pass Laser Frequency Conversion to 780.2 nm and 852.3 nm Based on PPMgO:LN Bulk Crystals and Diode-Laser-Seeded Fiber Amplifiers Kong Zhang 1, Jun He 1,2 and Junmin Wang 1,2,* 1 State Key Laboratory of Quantum Optics and Quantum Optics Devices, and Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China; [email protected] (K.Z.); [email protected] (J.H.) 2 Collaborative Innovation Center of Extreme Optics of the Ministry of Education and Shanxi Province, Shanxi University, Taiyuan 030006, China * Correspondence: [email protected] Received: 16 October 2019; Accepted: 15 November 2019; Published: 17 November 2019 Abstract: We report the preparation of a 780.2 nm and 852.3 nm laser device based on single-pass periodically poled magnesium-oxide-doped lithium niobate (PPMgO:LN) bulk crystals and diode-laser-seeded fiber amplifiers. First, a single-frequency continuously tunable 780.2 nm laser of more than 600 mW from second-harmonic generation (SHG) by a 1560.5 nm laser can be achieved. Then, a 250 mW light at 852.3 nm is generated and achieves an overall conversion efficiency of 4.1% from sum-frequency generation (SFG) by mixing the 1560.5 nm and 1878.0 nm lasers. The continuously tunable range of 780.2 nm and 852.3 nm are at least 6.8 GHz and 9.2 GHz. By employing this laser system, we can conveniently perform laser cooling, trapping and manipulating both rubidium (Rb) and cesium (Cs) atoms simultaneously. This system has promising applications in a cold atoms Rb-Cs two-component interferemeter and in the formation of the RbCs dimer by the photoassociation of cold Rb and Cs atoms confined in a magneto-optical trap.
    [Show full text]
  • Second Harmonic Generation in Nonlinear Optical Crystal
    Second Harmonic Generation in Nonlinear Optical Crystal Diana Jeong 1. Introduction In traditional electromagnetism textbooks, polarization in the dielectric material is linearly proportional to the applied electric field. However since in 1960, when the coherent high intensity light source became available, people realized that the linearity is only an approximation. Instead, the polarization can be expanded in terms of applied electric field. (Component - wise expansion) (1) (1) (2) (3) Pk = ε 0 (χ ik Ei + χ ijk Ei E j + χ ijkl Ei E j Ek +L) Other quantities like refractive index (n) can be expanded in terms of electric field as well. And the non linear terms like second (E^2) or third (E^3) order terms become important. In this project, the optical nonlinearity is present in both the source of the laser-mode-locked laser- and the sample. Second Harmonic Generation (SHG) is a coherent optical process of radiation of dipoles in the material, dependent on the second term of the expansion of polarization. The dipoles are oscillated with the applied electric field of frequency w, and it radiates electric field of 2w as well as 1w. So the near infrared input light comes out as near UV light. In centrosymmetric materials, SHG cannot be demonstrated, because of the inversion symmetries in polarization and electric field. The only odd terms survive, thus the second order harmonics are not present. SHG can be useful in imaging biological materials. For example, the collagen fibers and peripheral nerves are good SHG generating materials. Since the SHG is a coherent process it, the molecules, or the dipoles are not excited in terms of the energy levels.
    [Show full text]
  • Nonlinear Optical Characterization of 2D Materials
    nanomaterials Review Nonlinear Optical Characterization of 2D Materials Linlin Zhou y, Huange Fu y, Ting Lv y, Chengbo Wang y, Hui Gao, Daqian Li, Leimin Deng and Wei Xiong * Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China; [email protected] (L.Z.); [email protected] (H.F.); [email protected] (T.L.); [email protected] (C.W.); [email protected] (H.G.); [email protected] (D.L.); [email protected] (L.D.) * Correspondence: [email protected] These authors contributed equally to this work. y Received: 7 October 2020; Accepted: 30 October 2020; Published: 16 November 2020 Abstract: Characterizing the physical and chemical properties of two-dimensional (2D) materials is of great significance for performance analysis and functional device applications. As a powerful characterization method, nonlinear optics (NLO) spectroscopy has been widely used in the characterization of 2D materials. Here, we summarize the research progress of NLO in 2D materials characterization. First, we introduce the principles of NLO and common detection methods. Second, we introduce the recent research progress on the NLO characterization of several important properties of 2D materials, including the number of layers, crystal orientation, crystal phase, defects, chemical specificity, strain, chemical dynamics, and ultrafast dynamics of excitons and phonons, aiming to provide a comprehensive review on laser-based characterization for exploring 2D material properties. Finally, the future development trends, challenges of advanced equipment construction, and issues of signal modulation are discussed. In particular, we also discuss the machine learning and stimulated Raman scattering (SRS) technologies which are expected to provide promising opportunities for 2D material characterization.
    [Show full text]
  • Efficient Frequency Doubling at 399Nm Arxiv:1401.1623V3 [Physics
    Efficient Frequency Doubling at 399 nm Marco Pizzocaro,1, 2, ∗ Davide Calonico,2 Pablo Cancio Pastor,3, 4 Jacopo Catani,3, 4 Giovanni A. Costanzo,1 Filippo Levi,2 and Luca Lorini2 1Politecnico di Torino, Dipartimento di Elettronica e Telecomunicazioni, C.so duca degli Abruzzi 24, 10125 Torino, Italy 2Istituto Nazionale di Ricerca Metrologica (INRIM), Str. delle Cacce 91, 10135 Torino, Italy 3Istituto Nazionale di Ottica (INO-CNR), Via Nello Carrara, 1, 50019 Sesto Fiorentino, Italy 4European Laboratory for Non-Linear Spectroscopy (LENS), Via Nello Carrara, 1, 50019 Sesto Fiorentino, Italy (Dated: May 22, 2014) Abstract This article describes a reliable, high-power, and narrow-linewidth laser source at 399 nm useful for cooling and trapping of ytterbium atoms. A continuous-wave titanium-sapphire laser at 798 nm is frequency doubled using a lithium triborate crystal in an enhancement cavity. Up to 1:0 W of light at 399 nm has been obtained from 1:3 W of infrared light, with an efficiency of 80 %. arXiv:1401.1623v3 [physics.optics] 21 May 2014 ∗ Author to whom correspondence should be addressed. Electronic mail: [email protected] 1 Ytterbium holds interest for several atomic physics experiments because it is easy to cool and trap and has seven stable isotopes. Such experiments include optical frequency standards [1], non-conservation measurement [2], Bose-Einstein condensation [3], degenerate Fermi gases [4,5], bosonic-fermionic systems [6], and quantum information [7]. Ytterbium atoms can be cooled at millikelvin temperature using a magneto-optical trap (MOT) on the 1 1 strong blue transition S0− P1 at 399 nm.
    [Show full text]
  • Imaging with Second-Harmonic Generation Nanoparticles
    1 Imaging with Second-Harmonic Generation Nanoparticles Thesis by Chia-Lung Hsieh In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 2011 (Defended March 16, 2011) ii © 2011 Chia-Lung Hsieh All Rights Reserved iii Publications contained within this thesis: 1. C. L. Hsieh, R. Grange, Y. Pu, and D. Psaltis, "Three-dimensional harmonic holographic microcopy using nanoparticles as probes for cell imaging," Opt. Express 17, 2880–2891 (2009). 2. C. L. Hsieh, R. Grange, Y. Pu, and D. Psaltis, "Bioconjugation of barium titanate nanocrystals with immunoglobulin G antibody for second harmonic radiation imaging probes," Biomaterials 31, 2272–2277 (2010). 3. C. L. Hsieh, Y. Pu, R. Grange, and D. Psaltis, "Second harmonic generation from nanocrystals under linearly and circularly polarized excitations," Opt. Express 18, 11917–11932 (2010). 4. C. L. Hsieh, Y. Pu, R. Grange, and D. Psaltis, "Digital phase conjugation of second harmonic radiation emitted by nanoparticles in turbid media," Opt. Express 18, 12283–12290 (2010). 5. C. L. Hsieh, Y. Pu, R. Grange, G. Laporte, and D. Psaltis, "Imaging through turbid layers by scanning the phase conjugated second harmonic radiation from a nanoparticle," Opt. Express 18, 20723–20731 (2010). iv Acknowledgements During my five-year Ph.D. studies, I have thought a lot about science and life, but I have never thought of the moment of writing the acknowledgements of my thesis. At this moment, after finishing writing six chapters of my thesis, I realize the acknowledgment is probably one of the most difficult parts for me to complete.
    [Show full text]
  • Label-Free Multiphoton Microscopy: Much More Than Fancy Images
    International Journal of Molecular Sciences Review Label-Free Multiphoton Microscopy: Much More than Fancy Images Giulia Borile 1,2,*,†, Deborah Sandrin 2,3,†, Andrea Filippi 2, Kurt I. Anderson 4 and Filippo Romanato 1,2,3 1 Laboratory of Optics and Bioimaging, Institute of Pediatric Research Città della Speranza, 35127 Padua, Italy; fi[email protected] 2 Department of Physics and Astronomy “G. Galilei”, University of Padua, 35131 Padua, Italy; [email protected] (D.S.); andrea.fi[email protected] (A.F.) 3 L.I.F.E.L.A.B. Program, Consorzio per la Ricerca Sanitaria (CORIS), Veneto Region, 35128 Padua, Italy 4 Crick Advanced Light Microscopy Facility (CALM), The Francis Crick Institute, London NW1 1AT, UK; [email protected] * Correspondence: [email protected] † These authors contributed equally. Abstract: Multiphoton microscopy has recently passed the milestone of its first 30 years of activity in biomedical research. The growing interest around this approach has led to a variety of applications from basic research to clinical practice. Moreover, this technique offers the advantage of label-free multiphoton imaging to analyze samples without staining processes and the need for a dedicated system. Here, we review the state of the art of label-free techniques; then, we focus on two-photon autofluorescence as well as second and third harmonic generation, describing physical and technical characteristics. We summarize some successful applications to a plethora of biomedical research fields and samples, underlying the versatility of this technique. A paragraph is dedicated to an overview of sample preparation, which is a crucial step in every microscopy experiment.
    [Show full text]
  • Combined Two-Photon Excited Fluorescence and Second-Harmonic Generation Backscattering Microscopy of Turbid Tissues
    UC Irvine ICTS Publications Title Combined two-photon excited fluorescence and second-harmonic generation backscattering microscopy of turbid tissues Permalink https://escholarship.org/uc/item/2q9857fp Journal Proceedings of SPIE - The International Society for Optical Engineering, 4620 Authors Zoumi, A Yeh, AT Tromberg, BJ Publication Date 2002 License https://creativecommons.org/licenses/by/4.0/ 4.0 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Combined Two-Photon Excited Fluorescence and Second-Harmonic Generation Backscattering Microscopy of Turbid Tissues Aikaterini Zoumi a, b, Alvin T. Yeh a, and Bruce J. Tromberg a, b * aLaser Microbeam and Medical Program (LAMMP), Beckman Laser Institute, University of California, Irvine, CA 92612. bCenter for Biomedical Engineering, University of California, Irvine, CA 92612. ABSTRACT A broad range of excitation wavelengths (730-880nm) was used to demonstrate the co-registration of two- photon excited fluorescence (TPEF) and second-harmonic generation (SHG) in unstained turbid tissues in reflection geometry. The composite TPEF/SHG microscopic technique was applied to imaging an organotypic tissue model (RAFT). The origin of the image-forming signal from the various RAFT constituents was determined by spectral measurements. It was shown that at shorter excitation wavelengths the signal emitted from the extracellular matrix (ECM) is a combination of SHG and TPEF from collagen, whereas at longer excitation wavelengths the ECM signal is exclusively due to SHG. The cellular signal is due to TPEF at all excitation wavelengths. The reflected SHG intensity followed a quadratic dependence on the excitation power and exhibited a spectral dependence in accordance with previous theoretical studies.
    [Show full text]
  • Nobel Lecture, December 8, 2018 by Gérard Mourou University of Michigan, Ann Arbor, MI, USA & École Polytechnique, Palaiseau, France
    96 Extreme Light Physics and Application Nobel Lecture, December 8, 2018 by Gérard Mourou University of Michigan, Ann Arbor, MI, USA & École Polytechnique, Palaiseau, France. I. INTRODUCTION The advent of ultraintense laser pulses generated by the technique of chirped pulse amplifcation (CPA), along with the development of high-fuence laser materials has opened up entirely new felds of optics. A CPA laser exhibits stunning capabilities. It can generate the largest feld, the largest pressure, the highest temperature and accelerating feld, mak- ing it a universal source of high energy particles and radiation. CPA technology produces a wide range of intensities extending from 1014 to 1025 W/cm 2. In the lower part of this range, the intensity regimes of 1014 to 1017 have applications that include micromachining, which can be performed on material regardless of its nature, i.e. ceramic, metal, biologi- cal tissue, cornea, etc. Extremely clean cuts of minimal roughness even at the atomic scale are produced. This attractive property led us to applica- tions in ophthalmic procedures like refractive surgery, cataract surgery, corneal transplants and glaucoma treatment. Today, a million patients a year are benefting from femtosecond interventions. In science, in the same intensity level, CPA makes possible to reach the attosecond frontier, ofering a formidable tool to time resolved fundamental electronic pro- cesses. Gérard Mourou Lecture 97 For intensities >1018 W/cm 2 laser-matter interaction becomes strongly dominated by the relativistic character of the electron. In contrast to the nonrelativistic regime, the laser feld moves matter more efectively, including motion in the direction of laser propagation, nonlinear modula- tion and harmonic generation, leading to high energy particle and radia- tion production.
    [Show full text]
  • Nonlinear Optics in Daily Life
    Nonlinear optics in daily life Elsa Garmire* Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH, 03755, USA *[email protected] Abstract: An overview is presented of the impact of NLO on today’s daily life. While NLO researchers have promised many applications, only a few have changed our lives so far. This paper categorizes applications of NLO into three areas: improving lasers, interaction with materials, and information technology. NLO provides: coherent light of different wavelengths; multi-photon absorption for plasma-materials interaction; advanced spectroscopy and materials analysis; and applications to communications and sensors. Applications in information processing and storage seem less mature. © 2013 Optical Society of America OCIS codes: (190.0190) Nonlinear optics; (060.0060) Fiber optics and optical communications; (120.0120) Instrumentation, measurement, and metrology; (140.0140) Lasers and laser optics; (180.0180) Microscopy; (300.0300) Spectroscopy. References and Links 1. E. Garmire, “Overview of nonlinear optics,” open source, found at http://www.intechopen.com/books/nonlinear- optics/overview-of-nonlinear-optics. 2. E. Garmire, “Resource letter NO-1: nonlinear optics,” Am. J. Phys. 79(3), 245–255 (2011). 3. http://en.wikipedia.org/wiki/Laser_pointer. 4. http://www.coherent.com/products/?921/Mira-Family. 5. C. G. Durfee, T. Storz, J. Garlick, S. Hill, J. A. Squier, M. Kirchner, G. Taft, K. Shea, H. Kapteyn, M. Murnane, and S. Backus, “Direct diode-pumped Kerr-lens mode-locked Ti:sapphire laser,” Opt. Express 20(13), 13677– 13683 (2012). 6. http://www.continuumlasers.com/products/tunable_horizon_OPO.asp. 7. http://www.newport.com/Inspire-Automated-Ultrafast-OPOs/847655/1033/info.aspx.
    [Show full text]
  • Time-Resolved High-Harmonic Spectroscopy of Ultrafast Photo
    Time-resolved high-harmonic spectroscopy of ultrafast photo-isomerization dynamics Keisuke Kaneshima,* Yuki Ninota, and Taro Sekikawa Division of Applied Physics, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan *[email protected] Abstract We report the first study of time-resolved high-harmonic spectroscopy (TR-HHS) of a bond-making chemical reaction. We investigate the transient change of the high harmonic signal from 1,3-cyclohexadiene (CHD), which undergoes ring-opening and isomerizes to 1,3,5- hexatriene (HT) upon photoexcitation. By associating the change of the harmonic yield with the changes of the ionization energy and vibrational frequency of the molecule due to the isomerization, we find that the electronic excited state of CHD created via two-photon absorption of 3.1 eV photons relaxes almost completely within 80 fs to the electronic ground state of CHD with vibrational excitation. Subsequently, the molecule isomerizes abruptly to HT, i.e., ring-opening occurs, around 400 fs after the excitation. The present results demonstrate that TR-HHS, which can track both the electronic and the nuclear dynamics, is a powerful tool for unveiling ultrafast photo-chemical reactions. Body Measuring and understanding ultrafast dynamics in matter has always been a prime research goal. Recent developments of ultrashort-pulse light sources have allowed us to study electronic dynamics at the attosecond and angstrom scales, and progress has been made via high-harmonic generation (HHG), which provides attosecond pulses in the extreme ultraviolet (EUV) and enables the development of time-resolved techniques in the attosecond regime1–4. Not only as an ultrashort EUV light source, HHG process itself can also be used to investigate the state of the generating medium.
    [Show full text]
  • Periodically Poled Ridge Waveguides in KTP for Second Harmonic Generation in the UV Regime
    Vol. 26, No. 22 | 29 Oct 2018 | OPTICS EXPRESS 28827 Periodically poled ridge waveguides in KTP for second harmonic generation in the UV regime CHRISTOF EIGNER,1,* MATTEO SANTANDREA,1 LAURA PADBERG,1 MARTIN F. VOLK,2 CHRISTIAN E.RÜTER,2 HARALD HERRMANN,1 DETLEF KIP,2 AND CHRISTINE SILBERHORN1 1Department of Physics, University of Paderborn, 33098 Paderborn, Germany 2Faculty of Electrical Engineering, Helmut Schmidt University, 22043 Hamburg, Germany *[email protected] Abstract: Waveguide circuits play a key role in modern integrated optics and provide an appealing approach to scalability in quantum optics. We report on periodically poled ridge waveguides in z-cut potassium titanyl phosphate (KTiOPO4 or KTP), a material that has recently received growing interest due to its unique dispersion properties. Ridges were defined in surface-near rubidium-exchanged KTP by use of a precise diamond-blade dicing saw. We fabricated single- mode ridge waveguides at around 800 nm which exhibit widths of 1.9-3.2 µm and facilitated type-II second harmonic generation from 792 nm to 396 nm with high efficiency of 6.6 %/W·cm2. Temperature dependence of the second harmonic process was found to be 53 pm/K. The low temperature dependence and high nonlinear conversion efficiency make our waveguides ideally suited for future operations in classical nonlinear integrated optics and integrated quantum networking applications. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement OCIS codes: (130.0130) Integrated optics; (190.0190) Nonlinear optics; (230.0230) Optical devices. References and links 1. K. Kato “Temperature Insensitive SHG at 0.5321 µm in KTP,” IEEE J.
    [Show full text]
  • Second-Harmonic Spectroscopy JI Dadap and TF Heinz* Department
    Lasers in Physics: Second-Harmonic Spectroscopy J. I. Dadap and T. F. Heinz* Department of Physics and Department of Electrical Engineering Columbia University, 538 West 120 th St. New York, NY 10027 E-mail: [email protected] Introduction The demonstration of second-harmonic generation (SHG), one of the early experiments with pulsed lasers, is considered to have marked the birth of the field of nonlinear optics. The importance of second-harmonic generation, and the related phenomena of sum- and difference- frequency generation, as methods for producing new frequencies of coherent radiation was recognized immediately and has in no way diminished over the years. Associated with these applications came an interest in the fundamental nature of the second-order nonlinear response and some spectroscopic studies were undertaken with this motivation. This was a rather limited activity; it did not constitute a general method of optical probing of materials. In contrast, the third-order nonlinear optical interactions have given rise to a panoply of significant spectroscopic measurement techniques, including, to name a few, coherent Raman spectroscopy, pump-probe and other four-wave mixing measurements, two-photon absorption and hole burning measurements, photon echoes, and Doppler-free spectroscopy. A central factor in the lack of spectroscopic applications of the second-order nonlinear response lies in a fundamental symmetry constraint. Unlike the third-order nonlinearity, which 1 is present in all materials, only materials lacking a center of inversion give rise to an (electric- dipole) allowed second-order nonlinear response. As we demonstrate in this article, however, it is just this property that makes SHG, as well as the sum-frequency generation process discussed elsewhere in this encyclopedia, such a remarkable probe of surfaces and interfaces.
    [Show full text]