Semiconductor compounds: growth and application in nonlinear optics

The results of 25 years of development of ternary and binary semiconductor nonlinear CdGeAs₂, ZnGeP₂, AgGaSe ₂, Tl₃AsSe₃, GaSe crystal growth, doping and post growth treatment technologies, are summarized. Special attention has been paid to doped ZnGeP₂, GaSe and mixed AgGa _xIn_1-xSe₂, Ga_xIn_1-x Se crystals. The crystals grown are Ø20~30×60~100 mm in size and had absorption coefficients of α⩽0.01 cm^-1 at maximal transmission range. Post growth treatment techniques were developed to decrease optical losses in ZnGeP₂ crystals at the so called short-wavelength absorption “shoulder”. An analogous effect was reached by in-growth doping. The hardness of extra soft GaSe crystals was reached by In doping that gave the possibility to cut it with a diamond saw at any orientation and to polish. In addition good layer cohesion resulted in naturally high levels (about 70 pm/V) of second order nonlinear susceptibility. It was confirmed experimentally for the first time the possibility of 90° phase-matching in mixed crystals, in particular in AgGa_xIn_1-xSe₂ crystals. A large variety of near, middle and far IR harmonic, sum and difference frequency converters with efficiencies up to 80%, as well as broadband (Δλ=3.9-10 μm) and efficient OPOs were realized