BaGa4Se7 (BGSe) is the latest promising chalcogenide crystal with large nonlinear optical coefficients (d11 = 24.3 pm/V and d13 = 20.4 pm/V) and a wide transparency range of 0.47—18 microns [18-22]. The tuning range of the BGSe ORO with a 2.1 µm pump for type 1 was 3-5 microns, and the maximum output power reached 1.55 watts. The advantages of BGSe compared to ZnGeP2 are in the adjustment ranges and are related to the width of the transparency area. With ORO on BGSe type 2, tunable in the range of 8-9 microns, with a pumping of 2.1 microns, the maximum output power of an idle signal of 314 MW was obtained at a pumping radiation power of 9.58 W, which corresponds to a differential conversion efficiency of 7.44%, a quantum differential conversion efficiency of 32%. 

However, when studying parametric generation on BGSe, one significant factor was not taken into account: the crystal has cleavage along the crystallographic axes. When cleavage occurs, the crystal flakes off along certain flat grids of its structure. In the grown BaGa4Se7 crystal of a particularly large diameter along the growth direction, due to radiation scattering on cleavage planes, a dark brown color appears in the sample volume (Fig. 9), which leads to absorption in the sample and a decrease in resistance to laser breakdown. 

As a result of our research, two BaGa4Se7 crystals without cleavage planes were obtained (Fig. 10). The color of one crystal grown using one technology does not differ from the color of the stoichiometric composition of BaGa4Se7, and the optical element grown using another technology has a red color. 

These samples not only lack radiation scattering, but also increase the binding energy in the crystal lattice, which affects the optical qualities and generation characteristics of nonlinear frequency converters. Experiments have shown the absence of absorption in crystals and an increase in laser resistance of up to 30%, which will allow increasing the output power of the converted signal with increased sizes of nonlinear frequency converters.