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.
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.
Green power of 138 W was generated at an estimated beam quality of M(2) = 11 by intracavity frequency doubling of a diode-pumped Nd:YAG laser. The laser employs a diffusive close-coupled diode-pumping design and a bifocusing-compensation resonator design to ensure stable operation.
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)
We have improved the performances of InP-based HEMTs and MMICs for terahertz-wave wireless communications using a high frequency carrier wave around 300 GHz in an R&D program launched by the Ministry of Internal Affairs and Communications, Japan (MIC). Furthermore, we also have developed GaN and InSb-based HEMTs in another research. In this paper, we(More)