| Summary: | 3–5, 8–14 μm mid-far infrared (MF-IR) coherent lights generated by nonlinear optical (NLO) crystals are crucial for many industrial and military applications. AgGaGe<sub>5</sub>Se<sub>12</sub> (AGGSe) is a promising NLO candidate because of its good optical performance. In this paper, the large AGGSe single crystal of 35 mm diameter and 80 mm length was obtained by the seed-aided Bridgman method. The crystalline quality was characterized with X-ray diffraction, rocking curve, transmission spectrum. The FWHM of the (210) peak was about 0.05° and the IR transmission was about 60% (1–10 μm, 6 mm thick). Additionally, it performed well in 8 μm frequency doubling, with a maximum output power of about 41 mW, corresponding to an optical-to-optical conversion efficiency of 3.2%. The laser induced damage threshold (LIDT) value was about 200 MW/cm<sup>2</sup> (1.06 μm, 20 ns, 1 Hz).
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