Hisanori Fujita

Heavy fluorocarbon liquids for a phase-conjugated stimulated Brillouin scattering mirror.

Heavy fluorocarbon liquids were found to be an ideal medium for high-power stimulated Brillouin scattering experiments. Fluorinert FC-75 gives high reflectivity, near 98%, and excellent fidelity in phase conjugation of 14-J, 18-ns optical pulses. The complete removal of microparticle impurities was found to be essential for avoiding laser damage in a high-energy operation. A method of purification based on ultrafiltration has been developed.

Broadband high-gain pre-amplifier based on OPCPA for PW laser system

A broadband high-gain pre-amplifier using optical parametric chirped pulse amplification in the PW glass laser system has been developed. The output energy of 20 mJ without gain narrowing was obtained in a single pass through two BBO-OPCPA systems with good output stability.

High Repetition and High Average Power Nd:YAG Laser for EUV Lithography

We have been developing a high repetition (5-100 kHz) and high power Nd: YAG laser system pumped by cw LDs. Average power of 4.6 kW was obtained at 28.8 kW of pumping power.

Efficient Wavelength Conversion Based on Periodically Poled MgO:LiNbO 3 Optical Parametric Oscillator

Optical parametric oscillator based on a large aperture periodically poled MgO:LiNbO3 was used to generate 2 µm laser. Total output of 179 mJ with 53% slope efficiency was achieved at low pump fluence.

Experimental study on artificially triggered lightning using high power lasers

A series of laboratory experiments has been conducted to investigate the initiating effects of laser plasma channel on electrical discharge. It was confirmed that the plasma channels reduce the required electrical field strength for electrical discharges to occur by a factor of 6. A field experimental site targeting natural lightning is being prepared. The thunderstorm monitoring system and the laser and optical systems have been developed and tested against various weather conditions. The results from the laboratory experiments and field experiments will be discussed.