Ryusuke HORIUCHI, Koichi SAIKI, Koji ADACHI, Kazuyoku TEI, and Shigeru YAMAGUCHI

Department of Physics, Tokai University, Hiratsuka, Kanagawa 259-1292, Japan

(Received October 25, 2007; Accepted January 21, 2008)

A high-peak-power and high-repetition-rate fiber laser architecture is successfully demonstrated using a single-stage fiber amplifier. Nonlinear optical effects in a fiber amplifier degrade the monochromaticity of amplified laser pulses. In general, it is difficult for a non-monochromatic laser pulse to realize high-order harmonic generation with bulk nonlinear optical crystals. To overcome this problem, a single-stage amplifier architecture and a gain fiber with a high cladding absorption coefficient are employed. Furthermore, single-stage amplification enables the use of a multi-longitudinal mode electro-optically (EO) Q-switched micro seed laser. This architecture can generate a peak power of 100 kW at 50 kHz and an average power of 10 W. A second-harmonic conversion efficiency of 51% is obtained using this architecture and a LiB₃O₅ (LBO) crystal.

Key words: second-harmonic generation, fiber amplifier, high-peak-power, ytterbium, LBO