Focus issue introduction: Advanced Solid-State Lasers (ASSL) 2013 Yoonchan Jeong,1,* Shibin Jiang,2 Katia Gallo,3 Thomas Südmeyer,4 Markus Hehlen,5 and Takunori Taira6 1
Laser Engineering and Applications Laboratory, Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-744, South Korea 2 Advalue Photonics Inc., 3708 E. Columbia Street, Tucson, Arizona 857514, USA 3 KTH – Royal Institute of Technology, Department of Applied Physics, Roslagstullsbacken 21, SE-106 91 Stockholm, Sweden 4 Laboratoire Temps-Fréquence, Université de Neuchâtel, 2000 Neuchâtel, Switzerland 5 Los Alamos National Laboratory, Mailstop E549, Los Alamos, NM 87545, USA 6 Institute for Molecular Science, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan * [email protected]
Abstract: The editors introduce the focus issue on “Advanced Solid-State Lasers (ASSL) 2013,” which is based on the topics presented at a congress of the same name held in Paris, France, from October 27 to November 1, 2013. This focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 21 contributed papers (18 for Optics Express and 3 for Optical Materials Express) selected from the voluntary submissions from attendees who presented at the congress and have extended their work into complete research articles. We hope this focus issue offers a good snapshot of a variety of topical discussions held at the congress and will contribute to the further expansion of the associated research areas. ©2014 Optical Society of America OCIS codes: (060.0060) Fiber optics and optical communications; (130.0130) Integrated optics; (140.0140) Lasers and laser optics; (160.0160) Materials; (190.0190) Nonlinear optics; (230.0230) Optical devices; (320.0320) Ultrafast optics.
References and links 1. T. H. Maiman, “Stimulated optical radiation in ruby,” Nature 187(4736), 493–494 (1960). 2. Optics & Photonics Congress “Advanced Solid-State Lasers,” 27 October–1 November 2013, Paris, France (OSA Technical Digest, Washington DC, 2013). 3. Information available from http://www.osa.org/enus/meetings/optics_and_photonics_congresses/advanced_solid-state_lasers/scope_and_topic_categories/. 4. S. J. Yoon and J. I. Mackenzie, “Cryogenically cooled 946nm Nd:YAG laser,” Opt. Express 22(7), 8069–8075 (2014). 5. C. Larat, M. Schwarz, E. Lallier, and E. Durand, “120mJ Q-switched Er:YAG laser at 1645nm,” Opt. Express 22(5), 4861–4866 (2014). 6. J. R. Macdonald, S. J. Beecher, A. Lancaster, P. A. Berry, K. L. Schepler, S. B. Mirov, and A. K. Kar, “Compact Cr:ZnS channel waveguide laser operating at 2333 nm,” Opt. Express 22(6), 7052–7057 (2014). 7. G. Salamu, F. Jipa, M. Zamfirescu, and N. Pavel, “Laser emission from diode-pumped Nd:YAG ceramic waveguide lasers realized by direct femtosecond-laser writing technique,” Opt. Express 22(5), 5177–5182 (2014). 8. X. Peng, K. Kim, M. Mielke, S. Jennings, G. Masor, D. Stohl, A. Chavez-Pirson, D. T. Nguyen, D. Rhonehouse, J. Zong, D. Churin, and N. Peyghambarian, “Monolithic fiber chirped pulse amplification system for millijoule femtosecond pulse generation at 1.55 µm,” Opt. Express 22(3), 2459–2464 (2014). 9. C. P. João, H. Pires, L. Cardoso, T. Imran, and G. Figueira, “Dispersion compensation by two-stage stretching in a sub-400 fs, 1.2 mJ Yb:CaF2 amplifier,” Opt. Express (to be published). 10. J. Pouysegur, M. Delaigue, C. Hönninger, P. Georges, F. Druon, and E. Mottay, “Generation of 150-fs pulses from a diode-pumped Yb:KYW nonlinear regenerative amplifier,” Opt. Express (to be published). 11. S. Ishibashi and K. Naganuma, “Mode-locked operation of Cr4+:YAG single-crystal fiber laser with external cavity,” Opt. Express 22(6), 6764–6771 (2014). 12. M. Mangold, C. A. Zaugg, S. M. Link, M. Golling, B. W. Tilma, and U. Keller, “Pulse repetition rate scaling from 5 to 100 GHz with a high-power semiconductor disk laser,” Opt. Express 22(5), 6099–6107 (2014).
#209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8813
13. N. Tolstik, E. Sorokin, and I. T. Sorokina, “Graphene mode-locked Cr:ZnS laser with 41 fs pulse duration,” Opt. Express 22(5), 5564–5571 (2014). 14. N. Tolstik, A. Pospischil, E. Sorokin, and I. T. Sorokina, “Graphene mode-locked Cr:ZnS chirped-pulse oscillator,” Opt. Express 22(6), 7284–7289 (2014). 15. Y. Jeong, J. Sahu, D. Payne, and J. Nilsson, “Ytterbium-doped large-core fiber laser with 1.36 kW continuouswave output power,” Opt. Express 12(25), 6088–6092 (2004). 16. Information available from http://www.ipgphotonics.com and http://www.spilasers.com. 17. R. Piccoli, T. Robin, T. Brand, U. Klotzbach, and S. Taccheo, “Effective photodarkening suppression in Ybdoped fiber lasers by visible light injection,” Opt. Express 22(7), 7638–7643 (2014). 18. V. Agrež and R. Petkovšek, “Gain switch laser based on micro-structured Yb-doped active fiber,” Opt. Express 22(5), 5558–5563 (2014). 19. S. J. Augst, T. Y. Fan, and A. Sanchez, “Coherent beam combining and phase noise measurements of ytterbium fiber amplifiers,” Opt. Lett. 29(5), 474–476 (2004). 20. B. Rosenstein, A. Shirakov, D. Belker, and A. A. Ishaaya, “0.7 MW output power from a two-arm coherently combined Q-switched photonic crystal fiber laser,” Opt. Express 22(6), 6416–6421 (2014). 21. J. C. Knight, T. A. Birks, P. St. J. Russell, and D. M. Atkin, “All-silica single-mode optical fiber with photonic crystal cladding,” Opt. Lett. 21(19), 1547–1549 (1996). 22. A. Demircan, S. Amiranashvili, C. Brée, U. Morgner, and G. Steinmeyer, “Supercontinuum generation by multiple scatterings at a group velocity horizon,” Opt. Express 22(4), 3866–3879 (2014). 23. J. Kim, P. Dupriez, C. Codemard, J. Nilsson, and J. K. Sahu, “Suppression of stimulated Raman scattering in a high power Yb-doped fiber amplifier using a W-type core with fundamental mode cut-off,” Opt. Express 14(12), 5103–5113 (2006). 24. Y. Koyamada, S. Sato, S. Nakamura, H. Sotobayashi, and W. Chujo, “S, Nakamura, H. Sotobayashi, and W. Chujo, “Simulating and designing Brillouin gain spectrum in single mode fibers,” J. Lightwave Technol. 22(2), 631–639 (2004). 25. K. Park and Y. Jeong, “A quasi-mode interpretation of acoustic radiation modes for analyzing Brillouin gain spectra of acoustically antiguiding optical fibers,” Opt. Express 22(7), 7932–7946 (2014). 26. S. D. Grant and A. Abdolvand, “Evolution of conically diffracted Gaussian beams in free space,” Opt. Express 22(4), 3880–3886 (2014). 27. A. Kosuge, M. Mori, H. Okada, R. Hajima, and K. Nagashima, “Polarization-selectable cavity locking method for generation of laser Compton scattered γ-rays,” Opt. Express 22(6), 6613–6619 (2014). 28. Y. Sato and T. Taira, “Highly accurate interferometric evaluation of thermal expansion and dn/dT of optical materials,” Opt. Mater. Express 4(5), 876–888 (2014). 29. I. Yorulmaz, E. Beyatli, A. Kurt, A. Sennaroglu, and U. Demirbas, “Efficient and low-threshold Alexandrite laser pumped by a single-mode diode,” Opt. Mater. Express 4(4), 776–789 (2014). 30. H. Karakuzu, M. Dubov, S. Boscolo, L. A. Melnikov, and Y. A. Mazhirina, “Optimisation of microstructured waveguides in z-cut LiNbO3 crystals,” Opt. Mater. Express 4(3), 541–552 (2014).
The era of solid-state laser science and technology was opened by Maiman’s demonstration of “the flash-lamp-pumped ruby laser” in 1960, which is indeed the very first laser of all kinds [1]. Since then, we have seen remarkable, continuous advances in lasers, encompassing solidstate lasers and all other types of lasers. The progress includes a series of new scientific findings and technological developments in terms of materials, sources, and applications. As one premier example, the advent of semiconductor diode lasers combined with novel materials, such as crystals, ceramics, and fibers, has crowned solid-state lasers with unprecedented efficiency and flexibility. Over the last five decades, solid-state lasers have continuously been developed and deployed into numerous fields of our daily life, from a simple laser pointer to laser machinery for heavy industry or laser particle accelerators for high-energy physics. In fact, the 27 years of the former Advanced Solid-State Photonics (ASSP) meeting, together with Advances in Optical Materials (AIOM) and Fiber Laser Applications (FILAS) have served as an impetus to the mainstream of such advances, which were combined together in 2013 [2]. The Advanced Solid-State Lasers (ASSL) Congress 2013 was the inaugural meeting as one integrated congress, combining the three topical meetings formally known as ASSP, AIOM, and FILAS [2]. This historical, exciting new congress was held in Paris, France, from October 27 to November 1, 2013, offering researchers from all over the world great opportunities for presenting and discussing at one place their latest significant achievements in areas of materials, sources, and applications. Notwithstanding the radical change in the conference format, the ASSL Congress successfully managed to keep the style of topical meetings, running single-track technical sessions, which was greatly appreciated by attendees #209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8814
because no one needed to rush off to pick up presentations of interest. The single-track format indeed offered great stimulus for close interactions and networking among attendees and colleagues. The congress also provided selections of short courses and a series of special events, which also allowed for great encouragement and refreshment to attendees. The colocated topical meetings, including Application of Lasers for Sensing and Free-Space Communication (LS&C) and Mid-Infrared Coherent Sources (MICS), were another opportunity for looking around the recent advances in the associated research areas. The conference banquet at the historic Maison de la Chimine near the Pantheon and the Sorbonne, sponsored by IPG Photonics, was greatly enjoyed and appreciated by attendees. Finally, the Postdeadline Session (jointly with MICS) highlighted the utmost recent advances in materials, sources, and applications. It is worth noting that during the congress, 25 invited, 87 contributed oral, and 157 contributed poster papers were presented, together with 10 postdeadline papers. In general, the ASSL Congress includes topics categorized as follows [3]: Materials: • Laser crystals • Transparent ceramics • Crystal and glass fibers • Nonlinear crystals and processes • Waveguides and laser patterning • Photonics structures • Other materials used in lasers and optical devices Sources: • High power cw and pulsed fiber lasers • IR, visible, and UV fiber lasers • Diode-pumped lasers • Fiber lasers • Ceramic lasers • Laser beam combining • Short pulse lasers • Frequency-stable lasers • Tunable and new wavelength solid-state lasers • Optically pumped semiconductor lasers • High-brightness diodes • Optical sources based on nonlinear frequency conversion schemes Applications: • Cutting, precision marking, and welding applications • Sintering and powder deposition • Laser processing in photovoltaics, microelectronics, and flat panel displays
#209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8815
• Femtosecond optical micromachining • Homeland security and perimeter monitoring • Directed energy applications • Metrology, including optical frequency combs • Medicine and biological applications • Astronomical applications, including gravity wave detection and laser guide star This ASSL 2013 focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 21 contributed papers (18 for Optics Express and 3 for Optical Materials Express) selected from the voluntary submissions from attendees who presented at the ASSL Congress 2013 and have extended their work into complete research articles. While they do not cover the whole range of research topics presented and discussed at the congress, readers may be able to configure part of the foci of the presentations and discussions given at the congress, particularly in the following areas: Topics for Optics Express: • Ion doped crystal lasers (2) • Planar waveguide lasers (2) • Short pulse lasers (3) • Modelocked oscillators (4) • Fiber lasers (2) • Laser combining (1) • Nonlinear sources (1) • Nonlinear effects in fibers (1) • Optical technologies (2) Topics for Optical Materials Express: • Crystalline materials (1) • Laser materials (1) • Waveguide and optoelectronic devices (1) It is worth noting that the number given in parentheses denotes the number of contributed papers in the corresponding category. While it is not easy to divide all the contributed papers into separate categories with no conflict, the editors classify them, considering the primary focus of the work. Here we give brief introductions of the contributed papers as follows: Topics for Optics Express Ion doped crystal lasers: Solid-state lasers based on ion doped crystals having novel features are invariably of interest at all times. Two ion doped crystal lasers based on Nd:YAG and Er:YAG are discussed here [4,5]. Yoon et al. present the first multi-watt demonstration of a diode pumped cryogenically cooled Nd:YAG laser operating at 947 nm [4]. At the liquid nitrogen temperature (77 K), the authors obtained 3.8 W output power for 12.8 W of absorbed pump power with a slope efficiency of 47% under continuous wave (CW) operation. Another interesting point with this
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Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8816
paper is the authors’ extensive experimental study on the temperature-dependent spectroscopic properties of Nd:YAG. They found that an increase of ~2.5 times for both the absorption and emission cross-sections was obtainable when the gain medium was cooled down from 300 to 77 K. Larat et al. present an Er:YAG laser system comprising one oscillator and two single-pass amplifiers end-pumped by a fiber-coupled 1.47 μm diode [5]. The laser system could operate at 1.65 μm, capable of generating 120 mJ pulses with a beam quality factor (M2) of 3.1~3.7 at a repetition rate of 30 Hz. Although further pulse-energy scaling was limited by the damage of the pump dichroic mirrors, the authors think that there should still be room for improvement if a fiber-coupled diode laser system with higher power with the same brightness becomes available. Planar waveguide lasers: Waveguide lasers offer a great opportunity for generating coherent light in a very small dimension, which eventually allows for facilitating a variety of integrated optics applications. A number of waveguide fabrication techniques include ultrafast laser inscription and direct femtosecond-laser writing techniques [6,7]. Macdonald et al. present a compact mid-infrared channel waveguide based on Cr:ZnS, which was fabricated by ultrafast laser inscription technique and could operate at 2333 nm with a maximum power of 101 mW of CW output that was only limited by available pump power [6]. In particular, this wavelength is very useful for LIDAR, atmospheric sensing, and laser surgery. Salamu et al. report Nd:YAG ceramic waveguide lasers fabricated by direct femtosecondlaser writing technique [7]. Various waveguide geometries were investigated for CW and pulse operations at 1.06 and 1.3 μm wavelengths. For example, the authors could generate laser pulses of 2.8 mJ at 1.06 μm and of 1.2 mJ at 1.3 μm. Short pulse sources: High-energy short pulse sources are invariably of great importance because they facilitate numerous scientific and industrial applications. Possibly, this category is one of the most vivid research areas in solid-state laser science and technology. In general, to scale up the energy of the pulses in the ultrafast regime, very typical amplification techniques are utilized, such as chirped pulse amplification (CPA) or regenerative amplification [8–10]. Peng et al. present a monolithic fiber CPA system that could generate sub-500 fs pulses with 913 μJ pulse energy and 4.4 W average power at 1.55 μm wavelength, the estimated peak power of which approached 1.9 GW [8]. The authors highlight that the outstanding performance of this system was attributed to the straight and short length of the booster amplifier as well as to adaptive pulse shaping and spectral broadening techniques introduced to mitigate the overall nonlinear phase accumulation. They expect that additional system improvements, such as further increases in the effective mode area of the amplifier fiber, increasing Er-doping concentration, or longer pulse stretch factors, would lead to pulse energy well in excess of 1 mJ. João et al. present a CPA laser system generating 1.24 mJ, 390 fs pulses at 1035 nm, which comprised a 2.8 mJ Yb:CaF2 regenerative amplifier and a matched stretchercompressor device based on a single-chirped volume Bragg grating and a compact, lowdispersion Treacy compressor [9]. The authors highlight that the use of a Treacy grating pair at the stretcher substantially improved the output pulse length to a value of ~390 fs, which had otherwise been limited to 1.7 ps. Pouysegur et al. report the generation of 100-fs-level pulses obtained from an Yb:KYWbased regenerative amplifier [10]. The proposed innovative and simple femtosecond amplifier architecture was featured by the tailored control of the linear and nonlinear phase via the inclusion of a negative pre-chirper just after the seed laser. This allows for laser operations in 100-fs-level pulse duration, which have been accessible mainly with relatively more complicated Ti:sapphire-based ultrafast lasers. This pulse source eventually generated 32 μJ, 145 fs pulses centered at 1026 nm.
#209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8817
Modelocked oscillators: This category forms another vivid research area, providing seed lasers for short pulse source systems as well as being stand-alone sources for many other applications, such as optical combs, time-resolved measurements, imaging, etc. Ishibashi et al. report the first demonstration of a modelocked Cr4+:YAG single-crystal fiber laser operating at 1520 nm with 120 fs pulse duration and 23 mW output power in a single-pulse-per-round-trip configuration, which was obtained in a Z-fold cavity with a semiconductor saturable absorber mirror (SESAM) [11]. The authors emphasize that although the Cr4+:YAG single-crystal fiber could support multiple waveguide modes, a singletransverse-mode operation was obtained with the aid of the proper design of the external cavity. Mangold et al. present their recent study on a modelocked integrated external-cavity surface emitting laser (MIXSEL) [12]. In fact, this device facilitates stable and self-starting fundamental passive modelocking in a simple straight cavity, combining a vertical-externalcavity surface-emitting laser with a SESAM in a single semiconductor layer stack, with which the average power scaling is readily obtainable such as semiconductor disk lasers. The authors showed that a MIXSEL could support pulse repetition rate scaling from ~5 to >100 GHz with excellent beam quality and high average power. They could obtain average power of >1 W and pulse durations of
Laser Engineering and Applications Laboratory, Department of Electrical and Computer Engineering, Seoul National University, Seoul 151-744, South Korea 2 Advalue Photonics Inc., 3708 E. Columbia Street, Tucson, Arizona 857514, USA 3 KTH – Royal Institute of Technology, Department of Applied Physics, Roslagstullsbacken 21, SE-106 91 Stockholm, Sweden 4 Laboratoire Temps-Fréquence, Université de Neuchâtel, 2000 Neuchâtel, Switzerland 5 Los Alamos National Laboratory, Mailstop E549, Los Alamos, NM 87545, USA 6 Institute for Molecular Science, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan * [email protected]
Abstract: The editors introduce the focus issue on “Advanced Solid-State Lasers (ASSL) 2013,” which is based on the topics presented at a congress of the same name held in Paris, France, from October 27 to November 1, 2013. This focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 21 contributed papers (18 for Optics Express and 3 for Optical Materials Express) selected from the voluntary submissions from attendees who presented at the congress and have extended their work into complete research articles. We hope this focus issue offers a good snapshot of a variety of topical discussions held at the congress and will contribute to the further expansion of the associated research areas. ©2014 Optical Society of America OCIS codes: (060.0060) Fiber optics and optical communications; (130.0130) Integrated optics; (140.0140) Lasers and laser optics; (160.0160) Materials; (190.0190) Nonlinear optics; (230.0230) Optical devices; (320.0320) Ultrafast optics.
References and links 1. T. H. Maiman, “Stimulated optical radiation in ruby,” Nature 187(4736), 493–494 (1960). 2. Optics & Photonics Congress “Advanced Solid-State Lasers,” 27 October–1 November 2013, Paris, France (OSA Technical Digest, Washington DC, 2013). 3. Information available from http://www.osa.org/enus/meetings/optics_and_photonics_congresses/advanced_solid-state_lasers/scope_and_topic_categories/. 4. S. J. Yoon and J. I. Mackenzie, “Cryogenically cooled 946nm Nd:YAG laser,” Opt. Express 22(7), 8069–8075 (2014). 5. C. Larat, M. Schwarz, E. Lallier, and E. Durand, “120mJ Q-switched Er:YAG laser at 1645nm,” Opt. Express 22(5), 4861–4866 (2014). 6. J. R. Macdonald, S. J. Beecher, A. Lancaster, P. A. Berry, K. L. Schepler, S. B. Mirov, and A. K. Kar, “Compact Cr:ZnS channel waveguide laser operating at 2333 nm,” Opt. Express 22(6), 7052–7057 (2014). 7. G. Salamu, F. Jipa, M. Zamfirescu, and N. Pavel, “Laser emission from diode-pumped Nd:YAG ceramic waveguide lasers realized by direct femtosecond-laser writing technique,” Opt. Express 22(5), 5177–5182 (2014). 8. X. Peng, K. Kim, M. Mielke, S. Jennings, G. Masor, D. Stohl, A. Chavez-Pirson, D. T. Nguyen, D. Rhonehouse, J. Zong, D. Churin, and N. Peyghambarian, “Monolithic fiber chirped pulse amplification system for millijoule femtosecond pulse generation at 1.55 µm,” Opt. Express 22(3), 2459–2464 (2014). 9. C. P. João, H. Pires, L. Cardoso, T. Imran, and G. Figueira, “Dispersion compensation by two-stage stretching in a sub-400 fs, 1.2 mJ Yb:CaF2 amplifier,” Opt. Express (to be published). 10. J. Pouysegur, M. Delaigue, C. Hönninger, P. Georges, F. Druon, and E. Mottay, “Generation of 150-fs pulses from a diode-pumped Yb:KYW nonlinear regenerative amplifier,” Opt. Express (to be published). 11. S. Ishibashi and K. Naganuma, “Mode-locked operation of Cr4+:YAG single-crystal fiber laser with external cavity,” Opt. Express 22(6), 6764–6771 (2014). 12. M. Mangold, C. A. Zaugg, S. M. Link, M. Golling, B. W. Tilma, and U. Keller, “Pulse repetition rate scaling from 5 to 100 GHz with a high-power semiconductor disk laser,” Opt. Express 22(5), 6099–6107 (2014).
#209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8813
13. N. Tolstik, E. Sorokin, and I. T. Sorokina, “Graphene mode-locked Cr:ZnS laser with 41 fs pulse duration,” Opt. Express 22(5), 5564–5571 (2014). 14. N. Tolstik, A. Pospischil, E. Sorokin, and I. T. Sorokina, “Graphene mode-locked Cr:ZnS chirped-pulse oscillator,” Opt. Express 22(6), 7284–7289 (2014). 15. Y. Jeong, J. Sahu, D. Payne, and J. Nilsson, “Ytterbium-doped large-core fiber laser with 1.36 kW continuouswave output power,” Opt. Express 12(25), 6088–6092 (2004). 16. Information available from http://www.ipgphotonics.com and http://www.spilasers.com. 17. R. Piccoli, T. Robin, T. Brand, U. Klotzbach, and S. Taccheo, “Effective photodarkening suppression in Ybdoped fiber lasers by visible light injection,” Opt. Express 22(7), 7638–7643 (2014). 18. V. Agrež and R. Petkovšek, “Gain switch laser based on micro-structured Yb-doped active fiber,” Opt. Express 22(5), 5558–5563 (2014). 19. S. J. Augst, T. Y. Fan, and A. Sanchez, “Coherent beam combining and phase noise measurements of ytterbium fiber amplifiers,” Opt. Lett. 29(5), 474–476 (2004). 20. B. Rosenstein, A. Shirakov, D. Belker, and A. A. Ishaaya, “0.7 MW output power from a two-arm coherently combined Q-switched photonic crystal fiber laser,” Opt. Express 22(6), 6416–6421 (2014). 21. J. C. Knight, T. A. Birks, P. St. J. Russell, and D. M. Atkin, “All-silica single-mode optical fiber with photonic crystal cladding,” Opt. Lett. 21(19), 1547–1549 (1996). 22. A. Demircan, S. Amiranashvili, C. Brée, U. Morgner, and G. Steinmeyer, “Supercontinuum generation by multiple scatterings at a group velocity horizon,” Opt. Express 22(4), 3866–3879 (2014). 23. J. Kim, P. Dupriez, C. Codemard, J. Nilsson, and J. K. Sahu, “Suppression of stimulated Raman scattering in a high power Yb-doped fiber amplifier using a W-type core with fundamental mode cut-off,” Opt. Express 14(12), 5103–5113 (2006). 24. Y. Koyamada, S. Sato, S. Nakamura, H. Sotobayashi, and W. Chujo, “S, Nakamura, H. Sotobayashi, and W. Chujo, “Simulating and designing Brillouin gain spectrum in single mode fibers,” J. Lightwave Technol. 22(2), 631–639 (2004). 25. K. Park and Y. Jeong, “A quasi-mode interpretation of acoustic radiation modes for analyzing Brillouin gain spectra of acoustically antiguiding optical fibers,” Opt. Express 22(7), 7932–7946 (2014). 26. S. D. Grant and A. Abdolvand, “Evolution of conically diffracted Gaussian beams in free space,” Opt. Express 22(4), 3880–3886 (2014). 27. A. Kosuge, M. Mori, H. Okada, R. Hajima, and K. Nagashima, “Polarization-selectable cavity locking method for generation of laser Compton scattered γ-rays,” Opt. Express 22(6), 6613–6619 (2014). 28. Y. Sato and T. Taira, “Highly accurate interferometric evaluation of thermal expansion and dn/dT of optical materials,” Opt. Mater. Express 4(5), 876–888 (2014). 29. I. Yorulmaz, E. Beyatli, A. Kurt, A. Sennaroglu, and U. Demirbas, “Efficient and low-threshold Alexandrite laser pumped by a single-mode diode,” Opt. Mater. Express 4(4), 776–789 (2014). 30. H. Karakuzu, M. Dubov, S. Boscolo, L. A. Melnikov, and Y. A. Mazhirina, “Optimisation of microstructured waveguides in z-cut LiNbO3 crystals,” Opt. Mater. Express 4(3), 541–552 (2014).
The era of solid-state laser science and technology was opened by Maiman’s demonstration of “the flash-lamp-pumped ruby laser” in 1960, which is indeed the very first laser of all kinds [1]. Since then, we have seen remarkable, continuous advances in lasers, encompassing solidstate lasers and all other types of lasers. The progress includes a series of new scientific findings and technological developments in terms of materials, sources, and applications. As one premier example, the advent of semiconductor diode lasers combined with novel materials, such as crystals, ceramics, and fibers, has crowned solid-state lasers with unprecedented efficiency and flexibility. Over the last five decades, solid-state lasers have continuously been developed and deployed into numerous fields of our daily life, from a simple laser pointer to laser machinery for heavy industry or laser particle accelerators for high-energy physics. In fact, the 27 years of the former Advanced Solid-State Photonics (ASSP) meeting, together with Advances in Optical Materials (AIOM) and Fiber Laser Applications (FILAS) have served as an impetus to the mainstream of such advances, which were combined together in 2013 [2]. The Advanced Solid-State Lasers (ASSL) Congress 2013 was the inaugural meeting as one integrated congress, combining the three topical meetings formally known as ASSP, AIOM, and FILAS [2]. This historical, exciting new congress was held in Paris, France, from October 27 to November 1, 2013, offering researchers from all over the world great opportunities for presenting and discussing at one place their latest significant achievements in areas of materials, sources, and applications. Notwithstanding the radical change in the conference format, the ASSL Congress successfully managed to keep the style of topical meetings, running single-track technical sessions, which was greatly appreciated by attendees #209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8814
because no one needed to rush off to pick up presentations of interest. The single-track format indeed offered great stimulus for close interactions and networking among attendees and colleagues. The congress also provided selections of short courses and a series of special events, which also allowed for great encouragement and refreshment to attendees. The colocated topical meetings, including Application of Lasers for Sensing and Free-Space Communication (LS&C) and Mid-Infrared Coherent Sources (MICS), were another opportunity for looking around the recent advances in the associated research areas. The conference banquet at the historic Maison de la Chimine near the Pantheon and the Sorbonne, sponsored by IPG Photonics, was greatly enjoyed and appreciated by attendees. Finally, the Postdeadline Session (jointly with MICS) highlighted the utmost recent advances in materials, sources, and applications. It is worth noting that during the congress, 25 invited, 87 contributed oral, and 157 contributed poster papers were presented, together with 10 postdeadline papers. In general, the ASSL Congress includes topics categorized as follows [3]: Materials: • Laser crystals • Transparent ceramics • Crystal and glass fibers • Nonlinear crystals and processes • Waveguides and laser patterning • Photonics structures • Other materials used in lasers and optical devices Sources: • High power cw and pulsed fiber lasers • IR, visible, and UV fiber lasers • Diode-pumped lasers • Fiber lasers • Ceramic lasers • Laser beam combining • Short pulse lasers • Frequency-stable lasers • Tunable and new wavelength solid-state lasers • Optically pumped semiconductor lasers • High-brightness diodes • Optical sources based on nonlinear frequency conversion schemes Applications: • Cutting, precision marking, and welding applications • Sintering and powder deposition • Laser processing in photovoltaics, microelectronics, and flat panel displays
#209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8815
• Femtosecond optical micromachining • Homeland security and perimeter monitoring • Directed energy applications • Metrology, including optical frequency combs • Medicine and biological applications • Astronomical applications, including gravity wave detection and laser guide star This ASSL 2013 focus issue, jointly prepared by Optics Express and Optical Materials Express, includes 21 contributed papers (18 for Optics Express and 3 for Optical Materials Express) selected from the voluntary submissions from attendees who presented at the ASSL Congress 2013 and have extended their work into complete research articles. While they do not cover the whole range of research topics presented and discussed at the congress, readers may be able to configure part of the foci of the presentations and discussions given at the congress, particularly in the following areas: Topics for Optics Express: • Ion doped crystal lasers (2) • Planar waveguide lasers (2) • Short pulse lasers (3) • Modelocked oscillators (4) • Fiber lasers (2) • Laser combining (1) • Nonlinear sources (1) • Nonlinear effects in fibers (1) • Optical technologies (2) Topics for Optical Materials Express: • Crystalline materials (1) • Laser materials (1) • Waveguide and optoelectronic devices (1) It is worth noting that the number given in parentheses denotes the number of contributed papers in the corresponding category. While it is not easy to divide all the contributed papers into separate categories with no conflict, the editors classify them, considering the primary focus of the work. Here we give brief introductions of the contributed papers as follows: Topics for Optics Express Ion doped crystal lasers: Solid-state lasers based on ion doped crystals having novel features are invariably of interest at all times. Two ion doped crystal lasers based on Nd:YAG and Er:YAG are discussed here [4,5]. Yoon et al. present the first multi-watt demonstration of a diode pumped cryogenically cooled Nd:YAG laser operating at 947 nm [4]. At the liquid nitrogen temperature (77 K), the authors obtained 3.8 W output power for 12.8 W of absorbed pump power with a slope efficiency of 47% under continuous wave (CW) operation. Another interesting point with this
#209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8816
paper is the authors’ extensive experimental study on the temperature-dependent spectroscopic properties of Nd:YAG. They found that an increase of ~2.5 times for both the absorption and emission cross-sections was obtainable when the gain medium was cooled down from 300 to 77 K. Larat et al. present an Er:YAG laser system comprising one oscillator and two single-pass amplifiers end-pumped by a fiber-coupled 1.47 μm diode [5]. The laser system could operate at 1.65 μm, capable of generating 120 mJ pulses with a beam quality factor (M2) of 3.1~3.7 at a repetition rate of 30 Hz. Although further pulse-energy scaling was limited by the damage of the pump dichroic mirrors, the authors think that there should still be room for improvement if a fiber-coupled diode laser system with higher power with the same brightness becomes available. Planar waveguide lasers: Waveguide lasers offer a great opportunity for generating coherent light in a very small dimension, which eventually allows for facilitating a variety of integrated optics applications. A number of waveguide fabrication techniques include ultrafast laser inscription and direct femtosecond-laser writing techniques [6,7]. Macdonald et al. present a compact mid-infrared channel waveguide based on Cr:ZnS, which was fabricated by ultrafast laser inscription technique and could operate at 2333 nm with a maximum power of 101 mW of CW output that was only limited by available pump power [6]. In particular, this wavelength is very useful for LIDAR, atmospheric sensing, and laser surgery. Salamu et al. report Nd:YAG ceramic waveguide lasers fabricated by direct femtosecondlaser writing technique [7]. Various waveguide geometries were investigated for CW and pulse operations at 1.06 and 1.3 μm wavelengths. For example, the authors could generate laser pulses of 2.8 mJ at 1.06 μm and of 1.2 mJ at 1.3 μm. Short pulse sources: High-energy short pulse sources are invariably of great importance because they facilitate numerous scientific and industrial applications. Possibly, this category is one of the most vivid research areas in solid-state laser science and technology. In general, to scale up the energy of the pulses in the ultrafast regime, very typical amplification techniques are utilized, such as chirped pulse amplification (CPA) or regenerative amplification [8–10]. Peng et al. present a monolithic fiber CPA system that could generate sub-500 fs pulses with 913 μJ pulse energy and 4.4 W average power at 1.55 μm wavelength, the estimated peak power of which approached 1.9 GW [8]. The authors highlight that the outstanding performance of this system was attributed to the straight and short length of the booster amplifier as well as to adaptive pulse shaping and spectral broadening techniques introduced to mitigate the overall nonlinear phase accumulation. They expect that additional system improvements, such as further increases in the effective mode area of the amplifier fiber, increasing Er-doping concentration, or longer pulse stretch factors, would lead to pulse energy well in excess of 1 mJ. João et al. present a CPA laser system generating 1.24 mJ, 390 fs pulses at 1035 nm, which comprised a 2.8 mJ Yb:CaF2 regenerative amplifier and a matched stretchercompressor device based on a single-chirped volume Bragg grating and a compact, lowdispersion Treacy compressor [9]. The authors highlight that the use of a Treacy grating pair at the stretcher substantially improved the output pulse length to a value of ~390 fs, which had otherwise been limited to 1.7 ps. Pouysegur et al. report the generation of 100-fs-level pulses obtained from an Yb:KYWbased regenerative amplifier [10]. The proposed innovative and simple femtosecond amplifier architecture was featured by the tailored control of the linear and nonlinear phase via the inclusion of a negative pre-chirper just after the seed laser. This allows for laser operations in 100-fs-level pulse duration, which have been accessible mainly with relatively more complicated Ti:sapphire-based ultrafast lasers. This pulse source eventually generated 32 μJ, 145 fs pulses centered at 1026 nm.
#209150 - $15.00 USD (C) 2014 OSA
Received 31 Mar 2014; published 7 Apr 2014 7 April 2014 | Vol. 22, No. 7 | DOI:10.1364/OE.22.008813 | OPTICS EXPRESS 8817
Modelocked oscillators: This category forms another vivid research area, providing seed lasers for short pulse source systems as well as being stand-alone sources for many other applications, such as optical combs, time-resolved measurements, imaging, etc. Ishibashi et al. report the first demonstration of a modelocked Cr4+:YAG single-crystal fiber laser operating at 1520 nm with 120 fs pulse duration and 23 mW output power in a single-pulse-per-round-trip configuration, which was obtained in a Z-fold cavity with a semiconductor saturable absorber mirror (SESAM) [11]. The authors emphasize that although the Cr4+:YAG single-crystal fiber could support multiple waveguide modes, a singletransverse-mode operation was obtained with the aid of the proper design of the external cavity. Mangold et al. present their recent study on a modelocked integrated external-cavity surface emitting laser (MIXSEL) [12]. In fact, this device facilitates stable and self-starting fundamental passive modelocking in a simple straight cavity, combining a vertical-externalcavity surface-emitting laser with a SESAM in a single semiconductor layer stack, with which the average power scaling is readily obtainable such as semiconductor disk lasers. The authors showed that a MIXSEL could support pulse repetition rate scaling from ~5 to >100 GHz with excellent beam quality and high average power. They could obtain average power of >1 W and pulse durations of
