We describe tunable 5–12-μm mid-infrared generation in single-crystal silver gallium sulfide (AgGaS<sub>2</sub>), from nonlinear optical difference-frequency generation. Signal and idler waves obtained from a Nd:YAG laser–pumped LiNbO<sub>3</sub> optical parametric oscillator (OPO) were mixed in AgGaS<sub>2</sub> crystal to yield difference-frequency waves. For the efficient generation of difference frequency, an unstable resonator was employed as the OPO to reduce output beam divergence. A maximum difference-frequency power of 95 μJ/pulse was obtained near 7.5 μm for a 1-cm-long AgGaS<sub>2</sub> crystal. Spectral noncritical phase matching within a specific tuning range was also investigated that permitted limited single-knob tuning (5.5–8.5 μm) of the difference-frequency generator.
© 1999 Optical Society of America
(140.3410) Lasers and laser optics : Laser resonators
(190.4400) Nonlinear optics : Nonlinear optics, materials
(190.4410) Nonlinear optics : Nonlinear optics, parametric processes
(190.4970) Nonlinear optics : Parametric oscillators and amplifiers
Sajjad Haidar, Koichiro Nakamura, Eiji Niwa, Katashi Masumoto, and Hiromasa Ito, "Mid-Infrared (5-12-μm) and Limited (5.5-8.5-μm) Single-Knob Tuning Generated by Difference-Frequency Mixing in Single-Crystal AgGaS2," Appl. Opt. 38, 1798-1801 (1999)