High-efficiency mid-infrared ZnGeP_2 optical parametric oscillator directly pumped by a lamp-pumped, Q-switched CrTmHo:YAG laser

Abstract

We report a singly resonant optical parametric oscillator (SRO) based on a ZnGeP(2) crystal directly pumped by a lamp-pumped Q-switched CrTmHo:YAG laser. The IR was tunable from 4.7 to 7.8 microm via crystal angle tuning. A maximum optical to optical efficiency of 56% was obtained from the pump (2.09 microm) to total IR at a pump energy of 6.5 mJ. The corresponding idler energy was 1.45 mJ. The SRO was measured to have a slope efficiency of 64% and a threshold of 1 mJ. The spatial beam quality of the idler, characterized by the M(2) parameter, was 1.38 when the SRO was pumped at 2.5 times threshold. These results show that ZnGeP(2) optical parametric oscillators directly pumped by a CrTmHo:YAG laser can be operated efficiently, while maintaining good IR beam quality.

Ho:YAG laser pumped walk-off compensated mid-infrared ZGP optical parametric oscillation

“…The two end surfaces of the crystal are anti-reflection (AR) coated for wavelengths of 2.1 μm and 4.2 μm. At the pump wavelength, the absorption coefficient of the ZGP crystal is measured to be 0.04 cm -1 , which is slightly higher than the samples used in some of the previous work [1]. The experimental setup for the ZGP OPO and the WOC resonator is sketched in Fig.1.…”

“…ZnGeP 2 (ZGP) crystals have been extensively used for mid-infrared generation through optical parametric oscillations (OPOs) [1][2][3][4][5][6][7][8][9][10][11]. The material has high nonlinear susceptibility (d 36~7 5 pm/V), however, a relatively low laser damage threshold (1-2 J/cm 2 at 2.05 μm) [12,13].…”

Langasite Family Midinfrared Nonlinear Optical Oxide Materials: Structure, Property, and Applications

“…Moreover, the -axis electrical resistance of KTP is too low to bear highpower lasers so as to cause gray-tracking damage. Recently, high-resistance RTP crystals have been used for EO Q-switch applications [35]. At present, no better crystals have been found to fulfil the demand of high-performance EO Qswitches, especially those lasers that generate high repetition rates.…”

Development of a mid-infrared tunable optical parametric oscillator pumped by a Q-switched Tm,Ho:YAG laser

“…Although the OPO is more suitable for the miniaturization of the MIR tunable lasers, most MIR-OPOs have been pumped at the wavelength of 2-3 µm generated with another OPO pumped by a Nd:YAG laser at the wavelength of 1.064 µm [12][13][14][15][16] . Since such tandem OPO configurations complicate equipments and their overall efficiencies are low, MIR-OPOs directly pumped by a laser with a wavelength of 2-3 µm generated by lamp-pumped Ho:YLF, Er,Cr,Tm:YSGG, and Cr,Tm,Ho:YAG lasers have been reported [17][18][19][20] . However, the lasers in the 2-3 µm wavelength range have not been established well and their stabilities have been low compared with the lasers in the 1 µm wavelength range.…”