OP-GaAs OPO Pumped by 2μm Q-switched Lasers: Tm;Ho:Silica Fiber Laser and Ho:YAG Laser

Improvement in hybrid vapour phase epitaxy growing techniques of quasi-phase-matched orientation-patterned GaAs (OP-GaAs) allows larger sample thickness and permits efficient operation as a mid-infrared optical parametric oscillator at Watt-level average output powers [1-3]. Especially its low absorption loss (similar to 0.01 cm(-1)), its laser damage threshold comparable to ZGP (similar to 2 J/cm(2)) combined with a large nonlinear coefficient, a good thermal conductivity, excellent mechanical properties, and a wide transparency range (0.9-17 mu m) are suitable properties for efficient non-critical phase matched OPOs. As there is no natural birefringence in GaAs, phase matching is independent of polarization and propagation direction, offering the ability to pump OP-GaAs with a variety of polarization states. Thus, even unpolarized or poorly polarized sources like simple fiber lasers have been efficiently used as pump sources [4-5]. The paper discuss the best OP-GaAs OPO results achieved, to our knowledge, using a Q-switched 2.09 mu m Ho:YAG laser as pump source as well as results obtained with an OP-GaAs OPO directly pumped by a 2.09 mu m Q-switched Tm,Ho:silica fiber laser. With a 2.09 mu m Q-switched Ho: YAG fiber laser pump source up to 2.9 W of average output power was achieved at 20 kHz repetition rate, 3.9 W at 40 kHz and 4.9 W at 50 kHz. With a 2.09 mu m Q-switched Tm3+,Ho3+:silica fiber laser pump source, up to 2.2 W of average output power was achieved at 40 kHz repetition rate, 1.9 W at 60 kHz and 1.3 W at 75 kHz in the mid-infrared range