High-efficiency mid-infrared ZnGeP_(2) optical parametric oscillator directly pumped by a lamppumped, Q-switched CrTmHo:YAG laser

摘要

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 (mu)m via crystal angle tuning. A maximum optical to optical efficiency of 56percent was obtained from the pump (2.09 (mu)m) 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 64percent 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.