Diode-pumped cw and Q-switched Nd:GdVO 4 laser operating at 1.34 lm J. LIU 1, *, B. OZYGUS 1 , J. ERHARD 1 , A. DING 1 , H. WEBER 1 AND X. MENG 2 1 Optisches Institut (Sekr. P 1-1), Technische Universita ¨t Berlin, Str. des 17. Juni 135, D-10623 Berlin, Germany 2 National Laboratory of Crystal Materials, Shandong University, Jinan 250100, China (*author for correspondence: E-mail: junhai_liu@hotmail.com) Received 16 December 2002; accepted 10 February 2003 Abstract. A diode-pumped 1.34 lm Nd:GdVO 4 laser operating in cw and active Q-switching modes has been demonstrated. 4.15 W of cw output power was obtained at the highest attainable pump power of 12.3 W, resulting in an optical conversion efficiency of 33.7%, the slope efficiency was determined to be 37.6%. In Q-switching operation, a maximum average output power of 2.7 W was generated at pulse repetition frequency (PRF) of 50 kHz, with an optical conversion efficiency of 22% and a slope efficiency of 29.2%. The laser pulses with shortest duration, highest energy and peak power were achieved at PRF of 10 kHz, the parameters being 15 ns, 160 lJ, and 10.7 kW, respectively. By intracavity frequency-doubling with a type II phased-matched KTP crystal, 0.62 W average power at 0.67 lm was produced at a PRF of 15 kHz, the resulting pulse energy, peak power, and pulse width being 41.3 lJ, 2.2 kW, and 19 ns, respectively. A group of analytical formulae, based on rate equations, are presented to evaluate the operational parameters of an actively Q-switched laser. Calculated results were found to be in close consistency with the experimental data. Key words: diode-pumped, intracavity SHG, Nd:GdVO 4 laser, Q-switched 1. Introduction Since its first appearance a decade ago (Zagumennyi et al. 1992), the neo- dymium doped gadolinium vanadate crystal (Nd:GdVO 4 ) has attracted much attention of the researchers in the field of solid-state lasers, and has been recognized as a promising laser medium for diode pumping (Zhang et al. 2002). With regard to its laser properties, Nd:GdVO 4 is much similar to Nd:YVO 4 , currently the most widely used laser crystal for diode pumping in the low to medium power level regime. However, Nd:GdVO 4 possesses a unique ad- vantage over Nd:YVO 4 , its thermal conductivity along h110i directions is as high as 11.7 W m )1 K )1 , which is more than two times higher than that of Nd:YVO 4 , and comparable with that of Nd:YAG (about 14 W m )1 K )1 ) (Studenikin et al. 1995). This feature makes it attractive in many situations of application, such as operating on the transitions of 4 F 3/2 ! 4 I 13/2 (1.34 lm) Optical and Quantum Electronics 35: 811–824, 2003. Ó 2003 Kluwer Academic Publishers. Printed in the Netherlands. 811