Shuichi Fujikawa

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This paper proposes a new method of damping harmonic resonance at the DC-link of a large capacity rectifier-inverter system such as in rapid-transit railways. A voltage-source PWM converter is connected in series to the DC capacitor of the rectifier through a matching transformer, acting as a damping resistor to the DC capacitor current. No filters are(More)
We have demonstrated high-peak-power generation at 1 kW average power by applying an acousto-optic Q switch to a quasi-cw diode-pumped Nd:YAG master oscillator power amplifier. We achieved a maximum peak power of 2.3 MW by driving the Q switch in burst mode. The average repetition rate was 6 kHz. The corresponding beam quality was M2 = 9.
We have developed an all-solid-state 5-kHz Ti:sapphire laser system, which produces 22-fs, 0.2-TW pulses. An average power of 22.2 W is the highest ever obtained in ultrashort laser sources. The serious thermal lensing due to high power pumping in a small area of the Ti:sapphire crystal is controlled successfully by a stable quasi-cavity with two concave(More)
A transverse-flow radio-frequency-exited CO2 laser amplifier was evaluated by a short-pulse seed laser. We constructed a prototype transverse-flow amplifier for the extreme UV laser-produced-plasma source. The electrical power for the discharge was enhanced to 100 kW at a 100% duty cycle. A Q-switched cavity-dumped CO2 seed laser emitting 13 ns pulses with(More)
We constructed a master oscillator power amplifier CO2 laser system using a transverse-flow, RF-pumped CW CO2 laser. We carried out an amplification test at a 100% duty cycle of pumping discharge with the electrical input for the discharge up to 60 kW. An output power of 1.90 kW was achieved at the oscillator repetition rate of 100 kHz and the optical input(More)
An intracavity frequency-doubled diode side-pumped Nd:YAG laser was developed by use of an advanced cavity configuration and a diffusive close-coupled side-pumping design. A maximum green power of 68 W was generated at a 20-kHz repetition rate with 18.4% optical-to-optical conversion efficiency and 7.1% electrical-to-optical conversion efficiency.