Refractive Index Change Mechanisms in Different Glasses Induced by Femtosecond Laser Irradiation ", Proc

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A. Fuerbach ; S. Gross ; D. Little ; A. Arriola ; M. Ams ; P. Dekker and M. Withford " Refractive index change mechanisms in different glasses induced by femtosecond laser irradiation ", Proc. SPIE 9983, Pacific Rim Laser Damage 2016: Optical Materials for High-Power Lasers, 99830W (July 22, 2016)

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Invited Paper

Refractive index change mechanisms in different glasses induced by femtosecond laser irradiation

A. Fuerbach*, S. Gross, D. Little, A. Arriola, M. Ams, P. Dekker, M. Withford MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, North Ryde, NSW 2109, Sydney, Australia

ABSTRACT

Tightly focused femtosecond laser pulses can be used to alter the refractive index of virtually all optical glasses. As the laser-induced modification is spatially limited to the focal volume of the writing beam, this technique enables the fabrication of fully three-dimensional photonic structures and devices that are automatically embedded within the host material. While it is well understood that the laser-material interaction process is initiated by nonlinear, typically multiphoton absorption, the actual mechanism that results in an increase or sometimes decrease of the refractive index of the glass strongly depends on the composition of the material and the process parameters and is still subject to scientific studies. In this paper, we present an overview of our recent work aimed at uncovering the physical and chemical processes that contribute to the observed material modification. Raman microscopy and electron microprobe analysis was used to study the induced modifications that occur within the glass matrix and the influence of atomic species migration forced by the femtosecond laser writing beam. In particular, we concentrate on borosilicate, heavy metal fluoride and phosphate glasses. We believe that our results represent an important step towards the development of engineered glass types that are ideally suited for the fabrication of photonic devices via the femtosecond laser direct write technique.

Keywords: ultrafast phenomena, femtosecond laser direct-write technique, waveguide writing

1. INTRODUCTION Exactly 20 years ago, Davis et al. made a landmark discovery when they showed that femtosecond laser pulses with moderate energy can be used to induce a smooth and highly localized (i.e. localized to the focal volume of the femtosecond laser beam) refractive index change within different kinds of bulk glasses [1]. Since then, femtosecond laser direct-write photonics has evolved into a highly active research area in its own right with applications as diverse as quantum-optics, astro-photonics and integrated laser sources, to only name a few [2,3]. The main reason for the success of this technology lies in its apparent simplicity: A femtosecond laser beam is tightly focused into the bulk of a transparent sample which causes a localized material modification. By translating the sample with respect to the focal spot, arbitrary 3 dimensional (3-D) structures can be inscribed, see Figure 1. This process is often compared to writing structures with a pen on paper, yet the nature of the “pen” (a femtosecond laser) and the “paper” (a block of glass) imply that feature-sizes with sub- micron dimensions can be inscribed in a true 3-D fashion. 1.1 Underlying physical processes It is generally accepted that the physical phenomena that underlie the femtosecond laser direct-write technique can be described by three distinct processes with distinctively different time constants. In the first instant, the laser photons (typically at visible or near-infrared wavelengths) are absorbed by the electrons within the transparent material. As the photon energy is smaller than the bandgap of the material, this can only happen via nonlinear absorption processes which allow the laser energy to be deposited within the material (and not only at the surface) and also ensures that the modified volume is confined to the focal volume of the laser beam, where the electric field intensity is highest. Those nonlinear absorption processes are multiphoton and tunnel ionization (commonly described as strong electric field ionization, SEFI) as well as impact (avalanche) ionization. Kaiser et al. have shown that for laser pulses with durations in the order of

*[email protected]; phone +61 2 9850 6145

Pacific Rim Laser Damage 2016: Optical Materials for High-Power Lasers, edited by Takahisa Jitsuno, Jianda Shao, Wolfgang Rudolph, Proc. of SPIE Vol. 9983, 99830W © 2016 SPIE · CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2237368

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Femtosecond pulse train

Focusing objective

Waveguide

Sample

Sample translation direction

Figure 1. Ultrafast laser inscription setup: A femtosecond laser is tightly focused into the bulk of a transparent sample and nonlinear breakdown occurs, which causes a localized material modification. By translating the sample with respect to the focal spot, arbitrary 3 dimensional structures can be inscribed.

hundreds of femtoseconds, SEFI provides the initial seed electrons that enable the formation of a high-density electron gas in the conduction band via avalanche ionization processes. In contrast, for pulse durations below about 50 fs, SEFI alone can provide the critical number of electrons needed in the conduction band [4]. This entire process happens on the time scale of the incident laser pulse, i.e. is completed on a timescale of tens to hundreds of femtoseconds, depending on the pulse duration of the inscription laser. In a second step, these now “hot” electrons transfer their energy to the lattice via electron-phonon collisions, a process that takes place on a timescale of several picoseconds [4]. While those two initial steps, that eventually result in a localized modification of the refractive index of a transparent material are well understood and also largely material-independent processes, i.e. are processes that occur identically in virtually all transparent dielectrics that are irradiated by femtosecond laser pulses with moderate energy, it is the final step in the process that is still subject of intense research. Once the energy of the laser pulse has been transferred to the lattice, the nature of the refractive index modulation that is eventually induced within the bulk sample is strongly dependent on the exact material composition and is also strongly dependent on the laser parameters, in particular on the repetition frequency or repetition rate of the inscription laser. However, in all cases structural changes are induced in the glass-matrix and atomic species migration also plays an important role in the formation of the laser-induced refractive index change .

2. WRITING REGIMES

Athermal regime Thermal regime E 1ms E 200 ns tms due to i 1 Ns movement

} t

Figure 2. Athermal (low laser repetition rate) and thermal writing regime (high laser repetition rate).

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Due to the fact that typical heat diffusion times in glasses are in the order of 1 µs, a laser with a repetition frequency well below 1/ 1 µs = 1 MHz will result in a repetitive modification where each laser pulse interacts with “cold” material and the extent of the laser-modified volume solely depends on the shape of the focal volume of the laser beam (athermal regime). If lasers with repetition rates above 1 MHz are used, successive laser pulses result in a progressively increased temperature of the sample and therefore the extent of the modified volume can be controlled by the number of pulses incident on a certain volume within the sample, i.e. the translation speed of the sample (thermal regime) [5,6]. Figure 2 contrasts those two regimes.

We have demonstrated that in a multi-component Alkaline Earth Boro-Aluminosilicate glass (SiO2, Al2O3, B2O3, CaO, Corning Eagle 2000), tightly focused (i.e. to a focal spot of about 1 µm) high repetition rate laser pulses can be used to inscribe highly symmetric waveguides with diameters ranging from around 1 – 100 µm, depending on the laser pulse energy and the repetition rate, see Figure 3 [7]. Also, is has been found that those waveguides are highly stable and are not affected by photo-annealing. In contrast, we have also demonstrated that waveguides that are inscribed into Ytterbium- doped phosphate glass in the repetitive (athermal) modification regime are strongly affected by post-inscription photo- annealing [8]. We could show that the generation of visible light that is the result of cooperative luminescence of Ytterbium ions once they optically pumped, can almost entirely erase the previously inscribed waveguides. This shows that the physical process that lead to the change in refractive index must be fundamentally different in the thermal and the athermal regime, respectively. In order to investigate this phenomenon further and to provide a much more detailed analysis of the underlying physics involved, we performed a spatially-resolved Raman analysis.

3. BOROSILICATE GLASSES

0.016 0.10

0.016 - b) 0.08 0.014

0.012 - c 0.06 .1 0.010

0.006 - 004 1.520 6 0.006 -

Z 0.004 - z 0.02

0.002 - 1.519 0.000 0.00 6 3 -10 5 0 5 -15 -10 -5 0 5 10 15 1.518 Position (4n) Position (tun) 2

490 490 1.517 489 ' 489 É C) E 488 488 -5 0 -10 -5 0 5 E 487 Position (tun) Position (itm) 487 Á 486 486

485 485

Ú484 ¡484

483 483 -10 -15 -5 0 15 Position (ton) Position In m) Figure 4. (a) Refractive index, (b) 1400 cm−1 band intensity and (c) central wavenumber of the 518 cm−1 band as a function of position for waveguides written with a pulse repetition rate of 1 kHz (left) and 5 MHz (right). The insets show the two- dimensional (2D) refractive index profiles with the black line showing where the cross section was taken from. The writing laser propagated in the +y direction.

3.1 Raman studies For our investigations, we chose a very common crown glass with a relatively simple composition, i.e. the Borosilicate glass Schott BK 7. After measuring the Raman spectrum of the unmodified bulk glass, we inscribed a series of optical waveguides into the glass using two different laser sources with a repetition rate of 1 kHz and 5 MHz, i.e. in the thermal and the athermal regime, respectively. As can be seen in Figure 4 (a), the resulting refractive index change is remarkable different in those two cases. While the low repetition rate laser induces a fairly smooth and almost step-index-like refractive index modification profile, the MHz laser results in a more complex and highly modulated refractive index change. After the inscription process, we measured a series of Raman spectra across the modified regions with a spatial resolution of 2 µm. It can be seen in Figures 4(b) and (c) that the intensity of the 1400 cm−1 Raman band shows a clear modulation that

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resembles the refractive index profile in the kHz case remarkably well. In contrast, the intensity of this band does not change in the case of waveguides written with the MHz laser. On the other hand, the central wavenumber of the 518 cm−1 band shows a modulation that is proportional to the refractive index change in the MHz case whereas there is no change in position of this band for the kHz case. From this observations it can be concluded that an elevated population of Boron– Oxygen (B–O) units gives rise to the refractive index change in the athermal regime. Here, the laser pulses result in the formation of color-centers that give rise to non-bridging oxygen atoms and thus a change in molar refractivity. In the thermal regime, on the other hand, it is a decrease in the average Si–O bond length and thus an increase in the density of the glass that is responsible for the change in refractive index [9]. This also explains the fundamentally different behavior of the different waveguides in terms of photo-annealing as described before. 3.2 Selective Annealing Waveguides that were written into Corning Eagle 2000 glass in the thermal regime exhibited a fairly complex refractive −2 index profile as shown in Figure 5 (left). A central region with a high and positive index change (Δnmax ≈ 1×10 ) is surrounded by a ring of reduced refractive index change (depressed cladding, Δn ≈ -3×10−3) that, in turn, is surrounded by an outer ring of small and positive index change (Δn ≈ 3×10−3). It was suspected that those distinctively different regions were formed as a result of different physical mechanisms that happen during the writing process. To test this hypothesis, we performed a series of thermal annealing experiments on those waveguides. It turned out that it is indeed possible to selectively erase the outer ring alone, without affecting the inner regions at all, see Figure 5 (right) [10]. This indicates that the outer region is again a result of the formation of color centers (and thus not temperature-stable and subject to thermal annealing), whereas the inner regions are formed due to densification of the material, a process that cannot be reversed unless the material is heated above its melting point.

10-

-10 -

-15 -

-20

-20 -15 -10 0 5 10 15 2 -15 -10 -5 C. . 10 15 20 Postion (pm)

Figure 5. Refractive index profiles of waveguide written in the thremal regime in Corning Eagle 2000, measured before (left) and after annealing (right).

To further test and investigate the reason for the high temperature stability of the inner region, we performed an electron probe microanalysis that allowed us to spatially resolve the glass composition with a resolution of ≈ 2 µm. Figure 6 compares the refractive index profiles (top) before (left) and after (right) annealing with the glass composition within the

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waveguide region. It can clearly be seen that the femtosecond laser writing beam result in the migration of certain ions into the central waveguiding region (CaO, Al2O3) or out of that same region (SiO2).

0.6 0.4 0.4 0.2

0.2 0.0 0.0 -0.2 RI change [%] RI change [%] -0.2 -25 -20 -15 -10 -5 0 5 10 15 20 25 -25 -20 -15 -10 -5 0 5 10 15 20 25 2.0 1.5 CaO CaO 1.5 1.0 Al O Al O 1.0 2 3 2 3 SiO 0.5 SiO2 0.5 2 0.0

0.0

-0.5 -0.5 -1.0 -1.0 -1.5 -1.5 -2.0 Concentration change [wt%] Concentration change -25 -20 -15 -10 -5 0 5 10 15 20 25 Concentration change [wt%] Concentration change -25 -20 -15 -10 -5 0 5 10 15 20 25 Position [µm] Position [µm]

Figure 6. Refractive index profile (top) and composition of the glass (bottom) before (left) and after (right) annealing with the glass composition within the waveguide region.

This has also implication with regards to thermal poling of the glass, a process that allows the creation of a second-order nonlinearity in a centro-symmetric glass that does not feature any intrinsic second-order nonlinearity. As this technique is also based on a migration of certain ions within the glass (initiated by the applied electric poling field at elevated temperatures), the waveguide-writing process must also influence the poling process in a certain glass type. Indeed, as it turned out the induced nonlinear coefficient within laser-inscribed waveguides can exceed the nonlinear coefficient induced in bulk glass by almost an order of magnitude [11].

4. MID-INFRARED GLASSES

Material Source Glass /An Modification WG Mode Losses Crystal shape solution GLS ChG Southampton Sulphide An > 0 Vertically elongated - Single scan 46 pm 1.8 dB/cm (Commercial) (G) - Multiscan @3.39 pm @1.55 pm Naval Research Sulphide An < 0 Vertically elongated Stress waveguide 33 x 84 pm TBD AS39S61 Lab (G) @3.39 pm Dy:As2S3 Naval Research Sulphide An > 0 Vertically elongated - Single scan TBD TBD Lab (G) - Multiscan

Ge11.5 AS24S64.5 Australian National Sulphide An < 0 Vertically elongated Stress WIP TBD University (G)

Ge25 AS10S65 Australian National Sulphide An > 0 Vertically elongated Multiscan WIP TBD University (G)

Ge15 Sb20S65 Australian National Sulphide An < 0 Vertically elongated Stress waveguide WIP TBD University (G)

Ca F2 Edmund Optics Fluoride An < 0 Circular DISCARDED - X X Commercial (Crystal) Crystal ZBLAN University of Fluoride (G) An < 0 Circular Depressed 60 x 60pm 0.29 dB /cm Adelaide cladding @4 pm @4 pm InF3 University of Fluoride (G) An > 0 Circular Flowers -30 pm X Adelaide An ++for guiding @1.55 pm Pr:InF3 University of Fluoride (G) An > 0 Circular Flowers -30 pm X Adelaide An ++for guiding @1.55 pm La:InF3 University of Fluoride (G) An > 0 Circular Flowers -30 pm X Adelaide An ++for guiding @1.55 pm GASIR -1 Umicore Chalc. An < 0 Vertically elongated Stress waveguide WIP WIP Commercial

Table 1. Summary of waveguides written into various MIR glasses. WIP: Work in Progress. TBD: To be decided

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For many emerging applications, most notably Mid-infrared (MIR) spectroscopy and MIR astronomy (exoplanet hunting), the fabrication of photonic structures via the femtosecond laser direct-write technique in a glass that is transparent at the writing wavelength (normally 800 nm) and in the MIR (up to about 7 µm) is required. Suitable glasses are either chalcogenide glasses or fluoride glasses. Table 1 shows an overview of different glasses that have been investigated by us in terms of suitability for femtosecond laser waveguide inscription. As can be seen, ZBLAN, a heavy-metal fluoride glass (ZrF4-BaF2-LaF3-AlF3-NaF) is a glass that it perfectly suited for those applications due to the feasibility to inscribe highly symmetrical waveguides with extremely low losses via the so-called depressed-cladding architecture [12,13]. This becomes possible due to the fact that ZBLAN reacts with a highly symmetric negative refractive index change to irradiation with femtosecond laser pulses at high repetition rates (5 MHz in our case). In order to investigate the physical reasons for that observed behavior, we again performed a spatially resolved Raman analysis, see Figure 7. This study allowed us to conclude that in ZBLAN, the femtosecond laser pulses induce a decrease of the number of double bridging bonds and an increase of the number of single bridging bonds. As a single bridging bond is longer than a double bridging bond, this leads to the observed decrease in density and refractive index of the glass [14].

40000 Peak 1 579 cm -' 30000 Peak Pak 3 cß X70 cm' 40 cm -' 20000 Peak 4 Peak 6 Peak 2 c 35 cm -' a) 171 cm -' 489 cm -' -c 10000

0 200 300 400 500 600 700 Raman shift [cm -1]

Figure 7. Schematic of the composition of ZBLAN glass (left) and measured Raman spectrum (right), indicating the peaks that show a clear change within the waveguide region compared to the bulk glass.

5. CONCLUSIONS We have presented an overview of studies that were aimed at gaining a better understanding of the processes that are involved in the fabrication of photonic structures and devices via the femtosecond laser direct-write technique. Using spatially resolved Raman spectroscopy and electron probe microanalysis it was shown that the formation of color centers, material densification and ion migration play an important role and that the relative contribution of different processes highly depends on the host material and the laser process parameters. It was also demonstrated that a proper understanding of those process allows one to optimize the process, for example by utilizing selective annealing.

ACKNOWLEDGEMENTS

This research was supported by the Australian Research Council Centre of Excellence for Ultrahigh bandwidth Devices for Optical Systems (project number CE110001018) and was performed in part at the OptoFab node of the Australian National Fabrication Facility utilizing Commonwealth and NSW State Government funding.

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REFERENCES

[1] K.M. Davis, K. Miura, N. Sugimoto, K. Hirao: “Writing waveguides in glass with a femtosecond laser”, Opt. Letters 21, 1729 (1996) [2] R.R. Gattass, E. Mazur: “Femtosecond laser micromachining in transparent materials”, Nature Photonics 2, 219 (2008) [3] G. Palmer, S. Gross, A. Fuerbach, D.G Lancaster, M.J. Withford: “High slope efficiency and high refractive index change in direct-written Yb-doped waveguide lasers with depressed claddings”, Opt. Express 21, 17413 (2013) [4] A. Kaiser, B. Rethfeld, M. Vicanek, G. Simon: “Microscopic processes in dielectrics under irradiation by subpicosecond laser pulses”, Phys. Rev. B 61, 11437 (2000) [5] S.M. Eaton, H. Zhang, P.R. Herman, F. Yoshino, L. Shah, J. Bovatsek, A.Y. Arai: “Heat accumulation effects in femtosecond laser-written waveguides with variable repetition rate”, Opt. Express 13, 4708 (2005) [6] S. Gross, M. Ams, G. Palmer, C.T. Miese, R.J. Williams, G.D. Marshall, A. Fuerbach, D.G. Lancaster, H. Ebendorff-Heidepriem, M.J. Withford: “Ultrafast laser inscription in soft glasses: a comparative study of athermal and thermal processing regimes for guided wave optics”, Int. J. Appl. Glass Sci. 3, 332 (2012) [7] C. Miese, M.J. Withford, A. Fuerbach: “Femtosecond laser direct-writing of waveguide Bragg gratings in a quasi cumulative heating regime”, Opt. Express 19, 19542 (2011) [8] P. Dekker, M. Ams, G.D. Marshall, D.J. Little, M.J. Withford: “Annealing dynamics of waveguide Bragg gratings: evidence of femtosecond laser induced colour centres”, Opt. Express 18, 3274 (2010) [9] D.J. Little, M. Ams, S. Gross, P. Dekker, C.T. Miese, A. Fuerbach, M.J. Withford: “Structural changes in BK7 glass upon exposure to femtosecond laser pulses”, J. Raman Spectrosc. 42, 715 (2010) [10] A. Arriola, S. Gross, N. Jovanovic, N. Charles, P.G. Tuthill, S.M. Olaizola, A. Fuerbach, M.J. Withford: "Low bend loss waveguides enable compact, efficient 3D photonic chips," Opt. Express 21, 2978 (2013) [11] H.L. An, A. Arriola, S. Gross, A. Fuerbach, M.J. Withford, S. Fleming: “Creating large second-order optical nonlinearity in optical waveguides written by femtosecond laser pulses in boro-aluminosilicate glass”, Appl. Phys. Lett. 104, 021113 (2014) [12] D.G. Lancaster, S. Gross, H. Ebendorff-Heidepriem, K. Kuan, T.M. Monro, M. Ams, A. Fuerbach, M.J. Withford: “Fifty percent internal slope efficiency femtosecond direct-written Tm3+ :ZBLAN waveguide laser”, Opt. Letters 36, 1587 (2011) [13] S. Gross, M. Ams, D.G Lancaster, T.M. Monro, A. Fuerbach, M.J. Withford: “Femtosecond direct-write überstructure waveguide Bragg gratings in ZBLAN”, Opt. Letters 37, 3999 (2012) [14] S. Gross, D.G. Lancaster, H. Ebendorff-Heidepriem, T.M. Monro, A. Fuerbach, M.J. Withford: “Femtosecond laser induced structural changes in fluorozirconate glass”, Opt. Materials Express 3, 574 (2013)

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PROCEEDINGS OF SPIE

Pacific Rim Laser Damage 2016 Optical Materials for High-Power Lasers

Takahisa Jitsuno Jianda Shao Wolfgang Rudolph Editors

18–20 May 2016 Yokohama, Japan

Sponsored by SPIE

Organized by Institute of Laser Engineering, Osaka University (Japan) SPIE SIOM—Shanghai Institute of Optics and Fine Mechanics (China)

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Volume 9983

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Pacific Rim Laser Damage 2016: Optical Materials for High-Power Lasers, edited by Takahisa Jitsuno, Jianda Shao, Wolfgang Rudolph, Proc. of SPIE Vol. 9983, 998301 © 2016 SPIE · CCC code: 0277-786X/16/$18 · doi: 10.1117/12.2241075

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v Authors

vii Conference Committee

ix Introduction

LIC+PLD+SLPC JOINT SESSION 1

9983 04 Modeling of laser-induced damage and optic usage at the National Ignition Facility (Invited Paper) [9983-3]

PLENARY AND COATINGS

9983 08 Thin-film polarizer for high power laser system in China (Plenary Paper) [9983-7]

9983 0B Ion-assisted coating for large-scale Bimorph deformable mirror [9983-10]

SHORT PULSE PHENOMENA

9983 0M Spatial-temporal distortions and calibration of ultrashort pulses in complex optical systems [9983-21]

MATERIAL DAMAGE

9983 0S Laser damage measurement of thick silica plates using a new laser injection scheme (Invited Paper) [9983-37]

9983 0T Nanosecond laser damage of optical multimode fibers (Invited Paper) [9983-38]

9983 0U Adaptive laser beam forming for laser shock micro-forming for 3D MEMS devices fabrication (Invited Paper) [9983-39]

DEFECT, CONTAMINATION I

9983 0W Refractive index change mechanisms in different glasses induced by femtosecond laser irradiation (Invited Paper) [9983-41]

9983 0Z Enhanced internal reflection microscopy for subsurface damage inspection [9983-44]

iii

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Downloaded From: http://proceedings.spiedigitallibrary.org/ on 01/15/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx 9983 13 Optimization design and laser damage threshold analysis of pulse compression multilayer dielectric gratings [9983-48]

DEFECT, CONTAMINATION II

9983 14 Effectiveness of ion cleaning to improve the laser damage threshold of HfO2/SiO2 optical coatings for high reflection and antireflection at 527 nm and 1054 nm [9983-49]

9983 15 LIC and LID considerations in the design and implementation of the MEMS laser pointing mechanism for the EUSO UV laser altimeter [9983-50]

9983 16 Source of contamination in damage-test sample and vacuum [9983-51]

POSTER SESSION

9983 1A Effect of laser beam parameters on melt mobilization and LIBS analysis of a special aluminum alloy containing zeolite [9983-29]

9983 1B Ultrashort pulse laser slicing of semiconductor crystal [9983-30]

9983 1C Synthesis of fluorescent nanocarbons by femtosecond laser induced plasma in liquid [9983-31]

9983 1D Mitigation of BSG damage caused by upstream flaw in the final optics assembly [9983-32]

9983 1F Damage analysis of CMOS electro-optical imaging system by a continuous wave laser [9983-34]

9983 1G Study on the data matching of ground-based radar and laser point cloud [9983-35]

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Numbers in the index correspond to the last two digits of the six-digit citation identifier (CID) article numbering system used in Proceedings of SPIE. The first four digits reflect the volume number. Base 36 numbering is employed for the last two digits and indicates the order of articles within the volume. Numbers start with 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 0A, 0B...0Z, followed by 10-1Z, 20-2Z, etc.

Agatsuma, Naoki, 1C Mikami, Takuya, 0B, 16 Ams, M., 0W Miura, Kiyotaka, 1B, 1C Arriola, A., 0W Miyanaga, Noriaki, 0B, 16 Bai, Liang, 13 Motokoshi, Shinji, 0B, 16 Bellum, John C., 14 Murakami, H., 16 Bonville, O., 0S Nakimana, Agnes, 1A Bozzo, Enrico, 15 Neronov, Andrii, 15 Bude, Jeff, 04 Ni, Kaizao, 0Z Burch, Thomas, 15 Nostrand, Mike, 04 Carr, Wren, 04 Okamoto, Takayuki, 0B Chang, S. Q., 0M Penninckx, D., 0S Chen, A. Q., 0M Qiu, Zhiwei, 1G Chen, Kevin P., 0U Revol, Vincent, 15 Chen, Nana, 13 Sakakura, Masaaki, 1B, 1C Ciapponi, Alessandra, 15 Samarkin, Vadim V., 0B Courchinoux, R., 0S Shao, Jianda, 08, 0Z Dekker, P., 0W Shimotsuma, Yasuhiko, 1B, 1C Diaz, R., 0S Shin, Wan-Soon, 1F Fan, Shuwei, 13 Stanley, Ross, 15 Field, Ella S., 14 Sun, Mingying, 1D Fuerbach, A., 0W Suratwala, Tayyab I., 04 Fujimatsu, Yusei, 1C Wang, Chenxi, 1G Gross, S., 0W Wang, Mohan, 0U Heese, Clemens, 15 Wang, Shuliang, 0U Hoogerwerf, Arno, 15 Withford, M., 0W Huang, Sheng, 0U Xu, Longbo, 0Z Jhang, Kyung-Young, 1F Yi, Kui, 08 Jiao, Zhaoyang, 1D Yoon, Sunghee, 1F Jitsuno, Takahisa, 0B, 16 Yoshida, Kunio, 0B Kawanaka, Junji, 0B, 16 Yuan, F., 0M Kawasaki, T., 16 Yue, Jianping, 1G Khalil, Osama Mostafa, 1A Zhang, Bo, 0Z Kim, Eunho, 1B Zhang, H. Y., 0M

Kletecka, Damon E., 14 Zhao, Dongfeng, 1D Krüger, Jörg, 0T Zheng, Z. R., 0M Kudryashov, Alexis V., 0B Zhu, Jianqiang, 1D Lamaignère, L., 0S Zhu, L. J., 0M Lan, Nicholas, 15 Zhu, Meiping, 08 Li, Shuo, 0U Zhu, Rihong, 0Z Liao, Zhi M., 04 Zou, Ran, 0U Lin, Yankun, 0U

Little, D., 0W Liu, J., 0M Liu, S. Q., 0M Liu, Shijie, 0Z Liu, Xiaofeng, 0Z Luce, J., 0S Mann, Guido, 0T Mikami, K., 16

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Conference Chairs Takahisa Jitsuno, Osaka University (Japan) Jianda Shao, Shanghai Institute of Optics and Fine Mechanics (China) Wolfgang Rudolph, The University of New Mexico (United States)

Organizing Committee Hidetsugu Yoshida, Osaka University (Japan) Jyunji Kawanaka, Osaka University (Japan) Hajime Nishioka, Tokyo Electronic and Communication University (Japan) Tomozui Kamimura, Osaka Institute of Technology (Japan) Norihiko Yamamura, Showa Optronics Company, Ltd. (Japan) Kiyoshi Suda, Sigma Koki Company Ltd. (Japan) Minako Azumi, Nikon Corporation (Japan) Atsushi Yokotani, Miyazaki University (Japan) Ryo Yasuhara, National Institute for Fusion Science (Japan) Masayuki Fujita, Institute for Laser Technology (Japan)

International Program Committee Norbert Kaiser, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany) Efim A. Khazanov, Institute of Applied Physics (Russian Federation) Zunqi Lin, Shanghai Institute of Optics and Fine Mechanics (China) Yongfeng Lu, University of Nebraska-Lincoln (United States) Richard Moncorge, ENSICAEN (France) Jean-Yves Natoli, Institut Fresnel (France) Valdas Sirutkaitis, Vilnius University (Lithuania) Christopher J. Stolz, Lawrence Livermore National Laboratory (United States) Koji Sugioka, RIKEN (Japan) Takunori Taira, Institute for Molecular Science (Japan) Mauro Tonelli, Università di Pisa (Italy) Eric W. Van Stryland, CREOL, The College of Optics and Photonics, University of Central Florida (Florida) Zhouling Wu, Rx Technology Ltd. (China) Xiaomin Zhang, China Academy of Engineering Physics (China) Jiping Zou, École Polytechnique (France) Seong-Ku Lee, GIST-APRI (Korea, Republic of) Karol Adam Janulewicz, GIST-APRI (Korea, Republic of)

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Downloaded From: http://proceedings.spiedigitallibrary.org/ on 01/15/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx Session Chairs LIC+PLD+SLPC Joint Session I Kunihiko Washio, Paradigm Laser Research Ltd. (Japan)

LIC+PLD+SLPC Joint Session II Kunihiko Washio, Paradigm Laser Research Ltd. (Japan)

Plenary and Coatings Takahisa Jitsuno, Osaka University (Japan)

Nonlinear Materials Juan Du, Shanghai Institute of Optics and Fine Mechanics (China)

Short Pulse Phenomena Takahisa Jitsuno, Osaka University (Japan)

High Power Resistant Coatings Shinji Motokoshi, Institute for Laser Technology (Japan)

Material Damage Tomozui Kamimura, Osaka Institute of Technology (Japan)

Defect, Contamination I Kunie Yoshida, Okamoto Optical Works (Japan)

Defect, Contamination II Takahisa Jitsuno, Osaka University (Japan)

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Downloaded From: http://proceedings.spiedigitallibrary.org/ on 01/15/2017 Terms of Use: http://spiedigitallibrary.org/ss/termsofuse.aspx Introduction

As a part of Optics and Photonics International Congress (OPIC), we organized the 6th Pacific-Rim Laser Damage conference 2016 (PLD’16), held at Yokohama from 18 to 20 May 2016. This conference was co-sponsored by SPIE, and Shanghai Institute of Optics and Fine Mechanics (SIOM) in China. The PLD conference was started at 2009 by Prof. Jianda Shao at SIOM as a satellite meeting of the SPIE Laser Damage conference in Boulder, Colorado, USA, a conference with 48 years of history. The main purpose of PLD is to offer a chance to many Chinese research staff and students to contribute to an international conference. At the first PLD conference, Dr. K. Sugioka of Riken served as the co- chair from Japan. I joined at the 2nd meeting in 2011 at the request of Prof. J. Shao, and since the 3rd meeting in 2013, I have acted as a co-chair of the conference. The 4th PLD meeting was held in Yokohama, Japan in 2014 as part of the OPIC conference due to a strong request by Prof. J. Shao.

The PLD meeting is held biyearly in Shanghai, China, but PLD’14 and PLD’16 were held in Yokohama. These conferences were co-chaired by Prof. J. Shao and Prof. W. Rudolph, The Univ. of New Mexico (United States), just like the other PLD meetings. The International Program Committee of PLD’16 was the almost the exact same as PLD’15, and we selected Japanese members as the Organizing Committee.

Joint session with LIC, SLPC conferences

At this conference, we planned joint sessions with the Laser Ignition conference (LIC’16) and Smart Laser Process conference (SLPC’16) because these conferences have common interests in the interaction of laser light and matter. The PLD, LIC, and SLPC conferences each nominated two invited talks, and we had two joint sessions on 18 May 2016.

From PLD, findings on high power coating research and modeling of laser damage in NIF (National Ignition Facility) were reported. From LIC, semiconductor dicing and applications of microchip lasers were reported. From SLPC, paint removal and the fiver transportation of ultra-short pulses were reported.

I wish to express deep thanks to Mr. K. Washio for organizing this joint session.

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Oral and Invited talks

We had a total of 10 sessions including the poster session. We selected 10 invited talks according to the recommendations of the Program Committee members. One of them was the Plenary talk from SIOM reporting on the recent progress in high power optics, contamination problem and high power gratings. This talk was scheduled to be given by Prof. J. Shao, but unfortunately he could not come.

In the other 7 invited talks, selected speakers from 6 countries reported on the progress of their research. Most notably was the talk on harmonic generation from thin film coatings by The Univ. of New Mexico (United States). The promising point of this presentation was in the 10% harmonic conversion, which was possible in calculation without damage of the coating. This talk was planned as Prof. W. Rudolph’s talk, but he was not able to come and it was presented by another person.

Poster session

In the poster session, 7 reports were presented concerning resist removal, the fundamental process of metal processing, the semiconductor process, fine- particle generation, the anti-reflection nano-structure, CMOS camera damage, and the stress control of coatings.

Contributions

At the beginning of the abstract registration, we had 54 people submit abstracts through the SPIE submission site, however after the announcement of the program, 9 withdrawals were made and 10 presenters were absent, so the final presentation count was 35. The ratio of over-sea papers was 74%, and over-sea attendees were 63% because of the small domestic population of research activity in Japan.

The contributions were from China 11, United States 6, Japan 9, France 3, Germany, Austria, Switzerland, Lithuania, Egypt, and Korea 1 each, respectively.

Conclusions

PLD’16 was held as a part of the OPIC conferences in Yokohama, Japan. This system is very effective to support small international conferences, which is difficult to achieve alone. The author wishes to express deep thanks to the organizing members of OPIC and SPIE as the chair of PLD’16.

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OPTICS &PHOTONICS International Congress 2016

ALPS'16 BISC'16 . CLES2016 HEDS2016 - .}.-- LEDIA'16 LIC'16 ; --i LSSE2016 OMC'16 PLD'16 SLPC2016 XOPT'16

Date: May 17 (Tue) -20 (F0), 2016

Venue: Pacifico Yokohama, Conference Center _ iii

Takahisa Jitsuno

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