Ryo Yasuhara

Cryogenic temperature characteristics of Verdet constant on terbium gallium garnet ceramics

As the first demonstration of Faraday effect in a TGG ceramics, its Verdet constant at 1053 nm is evaluated to be 36.4 rad/Tm at room temperature which is same as that of the single crystal. In addition, the temperature dependence of Verdet constant is obtained experimentally. At liquid helium temperature, it is 87 times greater than that at room temperature.

213 W average power of 2.4 GW pulsed thermally controlled Nd:glass zigzag slab laser with a stimulated Brillouin scattering mirror

We report a high-average-power and high-pulse-energy diode-pumped Nd:glass laser amplifier system consisting of two thermally-edge-controlled zigzag slab amplifiers and a stimulated Brillouin scattering mirror. This phase-conjugated system produces an average power of 213 W at 10 Hz in a 8.9 ns pulse (2.4 GW peak power) with an optical-to-optical conversion efficiency of 11.7% and a near-diffraction-limited beam. To the best of our knowledge, this is the highest performance from a Nd:glass-based laser amplifier system ever built.

TGG ceramics based Faraday isolator with external compensation of thermally induced depolarization.

A Faraday isolator with compensation of thermally induced depolarization outside magnetic field was implemented for the first time on TGG ceramics. Stable isolation ratio of 38 dB in steady-state regime at a laser power of 300 W was demonstrated in experiment. Theoretical estimates show a feasibility of a device that would provide an isolation ratio higher than 30 dB up to laser power of 2kW.

84 dB amplification, 0.46 J in a 10 Hz output diode-pumped Nd:YLF ring amplifier with phase-conjugated wavefront corrector

A diode-pumped joule class in a 10 Hz output Nd:YLF ring amplifier has been developed. A phase conjugate plate was developed as a wavefront corrector for the residual wavefront distortion of an Nd:YLF rod. We have demonstrated a 0.46 J output of 10 ns pulse duration at 10 Hz repetition rate with 1.5 nJ of input energy. The effective gain of the ring amplifier system was 84.8 dB. To our knowledge, this is the highest magnification with joule-level output energy in a single-stage amplifier system that has ever been built. As a preamplifier system, this system contributed a demonstration of 21.3 J in a 10 Hz output diode-pumped Nd:glass zigzag slab laser system with a stimulated Brillouin scattering- phase conjugation mirror. We describe a robust and effective method of wavefront correction for high-energy laser systems.

Diode-Pumped Zig-Zag Slab Laser for Inertial Fusion Energy and Applications

A quasi-cw 290-kW diode-pumped zig-zag slab laser is being developed in order to demonstrate a concept of the IFE driver. Thermally managed amplifier has yielded a gain of 10, promising 10-J output at 10 Hz.

Design and Analysis on Face-Cooled Disk Faraday Rotator for High Average Power Lasers

A novel, scalable Faraday rotator has been designed for high-average-power lasers in a gas-cooled multi-disk scheme. The concept with a negligible thermal distortion and birefringence is feasible up to 10 kW/cm2 enough below fracture limit.

0.2 J, 100 Hz Cryogenic Laser by Using Yb:YAG Crystal

A diode-pumped MOPA laser system with 0.2-J pulse energy and 100-Hz repetition rate has been demonstrated with liquid-nitrogen-cooled Yb:YAG crystals. The slope efficiency was as high as 30% in the four-pass main amplifier.

Diode-Pumped Thermally Controlled Zig-Zag Slab Laser with 20-J Pulse Energy in 10 ns at 10-Hz Repetition Rate

20-J pulse energy in 10 ns at 10 Hz thermally controlled zig-zag slab laser based on the scaling law up to 100 J is being demonstrated by 800-kW peak pump power from 8,000 diode bars.

Temperature dependence of thermal expansion coefficient in ceramic and single crystal TGG

The temperature dependence of thermal expansion coefficient in the ceramic TGG was evaluated by using the Fizou interferometer method. It was corresponding to the of single crystal from 295 K to 86 K in our experiment.

Milli-Joules, Kilo-Hertz Regenerative Amplifier Using Total-Reflection Active-Mirror with Cryogenic Yb:YAG

A regenerative amplifier by using total-reflection active-mirror with a cryogenic YAG/Yb:YAG composite ceramics has been demonstrated up to kHz repetition rate. A 6.5-mJ pulse energy and a 9.3% optical efficiency were obtained at 200-Hz.