Prof. Akira Shirakawa Profile

Prof. Akira Shirakawa

Associate Professor at Univ of Electro-Communications

SPIE Involvement:

Author

Publications (17)

Proceedings Article | 5 March 2021 Presentation + Paper

Mode-locked seven-core multicore photonic crystal fiber laser with a saturable absorber

Tomonari Kawamura, Akira Shirakawa

Proceedings Volume 11665, 116651N (2021) https://doi.org/10.1117/12.2582719

KEYWORDS: Fiber lasers, Mode locking, Photonic crystal fibers, Laser crystals, Semiconductors, Semiconductor lasers, Resonators, Picosecond phenomena, Oscillators, Mirrors

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Proceedings Article | 11 March 2020 Presentation

Reinforcement learning for tiled aperture beam combining (Conference Presentation)

Henrik Tünnermann, Akira Shirakawa

Proceedings Volume 11260, 112600C (2020) https://doi.org/10.1117/12.2545578

KEYWORDS: Beam shaping, Phase shift keying, Modulation, Interferometry, Signal generators, Optical simulations, Neural networks, Evolutionary algorithms, Detection and tracking algorithms, Automatic control

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Proceedings Article | 13 March 2019 Presentation

Reinforcement learning for coherent beam combination (Conference Presentation)

Henrik Tünnermann, Akria Shirakawa

Proceedings Volume 10897, 108971D (2019) https://doi.org/10.1117/12.2509327

KEYWORDS: Coherent beam combination, Neural networks, Fiber lasers, Cameras, Sensors, Analog electronics, Feedback loops, Systems modeling, Femtosecond phenomena, Actuators

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Proceedings Article | 21 April 2017 Presentation

Coherent pulse stacking with delay lines (Conference Presentation)

Henrik Tünnermann, Akira Shirakawa

Proceedings Volume 10083, 1008305 (2017) https://doi.org/10.1117/12.2255868

KEYWORDS: Polarization, Oscillators, Phase shifts, Beam splitters, Pulsed fiber lasers, Fiber lasers, Bulk lasers, Switching, Femtosecond phenomena

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Proceedings Article | 7 March 2014 Paper

Single-frequency 1178nm SDL/Yb-PBGF MOPA with an output power of 31 W

Tomi Leinonen, Mingchen Chen, Xinyan Fan, Emmi Kantola, Akira Shirakawa, Mircea Guina

Proceedings Volume 8961, 896105 (2014) https://doi.org/10.1117/12.2040113

KEYWORDS: Fiber amplifiers, Semiconductor lasers, Semiconductors, Fiber lasers, Disk lasers, Optical amplifiers, Fabry–Perot interferometers, Polarization, Laser applications, Optical filters

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Proceedings Article | 16 February 2012 Paper

High-power single-frequency photonic bandgap fiber amplifier at 1178 nm

Meishin Chen, Akira Shirakawa, Yoshiaki Yamahara, Ken-ichi Ueda, Christina Olausson, Jens Lyngsø, Jes Broeng

Proceedings Volume 8237, 82371H (2012) https://doi.org/10.1117/12.908391

KEYWORDS: Raman spectroscopy, Fiber amplifiers, Amplifiers, Acoustics, Optical amplifiers, Fiber lasers, Optical isolators, Laser scattering, Scattering, Ytterbium

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Proceedings Article | 17 February 2010 Paper

Power-scalable long-wavelength Yb-doped photonic bandgap fiber sources

Christina Olausson, Akira Shirakawa, Hiroki Maruyama, Ken-ichi Ueda, Jens Lyngsø, Jes Broeng

Proceedings Volume 7580, 758013 (2010) https://doi.org/10.1117/12.845938

KEYWORDS: Fiber amplifiers, Fiber lasers, Amplifiers, Ytterbium, Cladding, Second-harmonic generation, Harmonic generation, Semiconductor lasers, Laser applications, Raman spectroscopy

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Proceedings Article | 12 August 2008 Paper

Power and energy-scaling of cladding-pumped Raman fibre lasers sources

C. Codemard, A. Shirakawa, J.-N. Maran, J. Sahu, J. Nilsson

Proceedings Volume 7099, 70990V (2008) https://doi.org/10.1117/12.806987

KEYWORDS: Raman spectroscopy, Fiber lasers, Cladding, Raman scattering, Beam propagation method, Mirrors, High power lasers, Multimode fibers, Absorption, Continuous wave operation

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Proceedings Article | 20 February 2007 Paper

Laser performance of Yb3+:YAG ceramic microchip lasers

Jun Dong, Akira Shirakawa, Ken-ichi Ueda, Hideki Yagi, Takagimi Yanagitani, Alexander Kaminskii

Proceedings Volume 6451, 645118 (2007) https://doi.org/10.1117/12.699056

KEYWORDS: Ceramics, YAG lasers, Chromium, Absorption, Ytterbium, Q switched lasers, Output couplers, Pulsed laser operation, Picosecond phenomena, Laser applications

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The optical properties of Yb:YAG ceramic doped with different Yb concentrations are presented. The absorption coefficient at peak absorption wavelength of 940 nm increases linearly with Yb concentration in Yb:YAG ceramics. Low-threshold and highly-efficient continuous-wave (cw) laser-diode end-pumped Yb:YAG microchip ceramic laser with near-diffraction-limited beam quality was demonstrated at room temperature. Slope efficiencies of 79%, 67% and optical-to-optical efficiency of 60%, 53% at 1030 nm and 1049 nm, respectively were achieved for 1-mm-thick Yb:YAG ceramic plate (C_Yb = 9.8 at.%) under cw laser-diode pumping. Dual-wavelength operation at 1030 nm and 1049 nm with 5% transmission of the output coupler was achieved by varying pump power intensity. 1049 nm laser operation was automatically obtained by using 5% transmission output coupler when absorbed pump power is higher than 1 W. The lasers operate in multi-longitudinal-mode; the effect of pump power on the laser emission spectra for both wavelengths is addressed. The laser wavelength around 1030 nm shifts to short wavelength at low pump power region and then to red with increase of the absorbed pump power, while the laser wavelength around 1049 nm does not change with the pump power. Excellent laser performance indicates Yb:YAG ceramic laser materials could be potentially used in high-power solid-state lasers operating at 1030 nm, 1049 nm, or both wavelengths simultaneously. Laser-diode pumped lowthreshold and highly-efficient passively Q-switched Yb:YAG ceramic microchip laser with Cr⁴⁺:YAG ceramic as saturable absorber has also been demonstrated. The slope efficiency is as high as 37%, and the optical-to-optical efficiency is as high as 29% for 89% initial transmission of Cr⁴⁺:YAG ceramic. The pulse width of 380 ps and peak power of over 82 kW at repetition rate of 12.4 kHz was obtained. Single-longitudinal-mode oscillation and wide-separated multi-longitudinal-mode oscillation due to etalon effect of Cr⁴⁺:YAG thin plate was achieved depending on the pump power level.

Proceedings Article | 8 September 2006 Paper

Switchable lasing of 1040- and 1537-nm lines based on the optical bistability in the pump-bypassed ytterbium-doped fiber laser

Jianlang Li, Mitsuru Musha, Akira Shirakawa, Ken-ichi Ueda

Proceedings Volume 6310, 63100G (2006) https://doi.org/10.1117/12.683812

KEYWORDS: Fiber lasers, Bistability, Ytterbium, Absorption, Wavelength division multiplexing, Fiber Bragg gratings, Fiber optic communications, Fiber optics, Laser optics, Free space optics

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Proceedings Article | 5 December 2005 Paper

Antiphase states of sub-nanosecond Cr,Yb:YAG microchip self-Q-switched multimode laser

Jun Dong, Akira Shirakawa, Ken-ichi Ueda

Proceedings Volume 6020, 60201C (2005) https://doi.org/10.1117/12.634969

KEYWORDS: Absorption, Pulsed laser operation, Numerical simulations, Q switched lasers, Crystals, Hole burning spectroscopy, Semiconductor lasers, Chromium, Continuous wave operation, Laser crystals

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Proceedings Article | 22 April 2005 Paper

CW 7-W 900-nm-wide supercontinuum source by phosphosilicate fiber Raman laser and high-nonlinear fiber

Akira Shirakawa, Ken-ichi Ueda

Proceedings Volume 5709, (2005) https://doi.org/10.1117/12.590401

KEYWORDS: Fiber lasers, Raman spectroscopy, Continuous wave operation, Supercontinuum generation, Absorption, Fiber Bragg gratings, Supercontinuum sources, Modulation, Four wave mixing

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Proceedings Article | 22 April 2005 Paper

Fiber laser coherent array for power scaling, bandwidth narrowing, and coherent beam direction control

Akira Shirakawa, Keigo Matsuo, Ken-ichi Ueda

Proceedings Volume 5709, (2005) https://doi.org/10.1117/12.590328

KEYWORDS: Fiber lasers, Fiber couplers, Reflectivity, Beam controllers, Resonators, Fiber Bragg gratings, Wavelength division multiplexing, Laser resonators, Laser damage threshold, Electro optics

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Proceedings Article | 23 March 2005 Paper

Novel cooling technique for operation of quasi four-level solid-state laser

Todor Petrov, K. Takaichi, Hitoki Yoneda, Akira Shirakawa, Ken-ichi Ueda, Nikola Sabotinov

Proceedings Volume 5777, (2005) https://doi.org/10.1117/12.611229

KEYWORDS: Nitrogen, Ceramics, Liquids, Helium, Solid state lasers, Femtosecond phenomena, Crystals, Argon, Absorption, Fiber optic gyroscopes

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Proceedings Article | 8 October 2004 Paper

Fiber laser coherent array for power scaling of single-mode fiber laser

Akira Shirakawa, Keigo Matsuo, Ken-ichi Ueda

Proceedings Volume 5662, (2004) https://doi.org/10.1117/12.596366

KEYWORDS: Fiber lasers, Fiber couplers, Beam controllers, Reflectivity, Resonators, Laser resonators, Single mode fibers, Fiber Bragg gratings, Laser applications, Laser processing

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Proceedings Article | 7 April 2004 Paper

Measurements of nonlinear refractive indices in ceramic laser media

Yuri Senatsky, Akira Shirakawa, Y. Sato, J. Hagiwara, Jianren Lu, Kichi Ueda, H. Yagi, T. Yanagitani

Proceedings Volume 5478, (2004) https://doi.org/10.1117/12.558509

KEYWORDS: Ceramics, Laser applications, Refractive index, Crystals, Laser crystals, Nonlinear crystals, Laser development, High power lasers, Pulsed laser operation, Laser spectroscopy

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Proceedings Article | 6 October 2003 Paper

Raman fiber laser-pumped 2-um fiber laser

Atsushi Taniguchi, Tetsuro Kuwayama, Akira Shirakawa, Mitsuru Musha, Ken-ichi Ueda, Mahendra Prabhu

Proceedings Volume 5137, (2003) https://doi.org/10.1117/12.517936

KEYWORDS: Fiber lasers, Optical fibers, Ions, Wavelength division multiplexing, Fiber couplers, Raman spectroscopy, Single mode fibers, Fiber Bragg gratings, Absorption, Neodymium

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