GaSe crystals with 0, 0.07, 0.38, 0.67, 2.07, 3, and 5 wt % Te are grown. GaSe:Te (≤2.07 wt %) crystals are suitable for nonlinear optics applications. The optimum doping level is 0.07 wt %. This minimizes optical losses and increases the damage threshold by ≥20%, hardness by 33%, and the efficiency of femtosecond Ti:Sa laser frequency conversion into the 8.8–24 μm and 0.2–3 THz ranges by ≥50%.