Widely tunable optical parametric oscillators (OPOs) are attractive sources for applications in mid-IR due to;the scarcity of direct-emitting conventional lasers in this spectral region. Recently, two new chalcogenide;compounds BaGa4Se7 (BGSe) and BaGaGe2Se6 (BGGSe) having relatively high χ(2) nonlinear optical coefficient;were successfully synthesized and large single crystals were grown using the Bridgman-Stockbarger technique;[1, 2]. Recently the first BGSe nanosecond OPO pumped by a Q-switched Nd:YAG laser (1.064 μm)  and;pumped at 2.09 μm by a Q-switched Ho:YAG laser  were demonstrated. Lastly, an intracavity pumped cascaded;OPO based on BGGSe was reported .
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