>100-kW Linearly Polarized Pulse Fiber Amplifier Seeded
by a Compact Efficient Passively Q-switched Nd:YVO₄ Laser¹

W. Z. Zhuang, W. C. Huang, C. Y. Cho, Y. P. Huang, J. Y. Huang, and Y. F. Chen*

Department of Electrophysics, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu, 30010, Taiwan

*e-mail: yfchen@cc.nctu.edu.tw

Received December 21, 2012; in final form, December 28, 2012; published online October 1, 2012

Abstract—We thoroughly develop compact high-peak-power Nd:YVO₄/Cr⁴⁺:YAG passively Q-switched
lasers (PQS) as the seed source of the fiber amplifier. We exploit a nearly hemispherical cavity to reach the sec-
ond threshold criterion and systematically consider the thermal lensing effect and the mode-size matching in
the overall optimization. Employing a Cr⁴⁺:YAG absorber with 70% initial transmission, we obtain a 50kHz
seed pulse train with the pulse duration of 4.8 ns and the pulse energy of 22 J at a pump power of 5.4W. Inject-
ing this seed laser into a polarization maintained Yb-doped fiber, the pulse energy and peak power at a pump
power of 16 W are enhanced up to 178 J and 37 kW, respectively. We also use an absorber with 40% initial
transmission to generate a 25 kHz pulse train with the pulse duration of 1.6 ns and the pulse energy of 36 J at
a pump power of 5.4 W. With this seed laser, we find that the surface damage of the fiber limits the maximum
pulse energy and peak power to be 192 J and 120 kW, respectively.

DOI: 10.1134/S1054660X12110205

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