Mastering of the middle IR range is attractive for many applications, such as lidar gas analyzers, optoelectronic
countermeasures for suppression of IR detecting, optical communication systems, and scientific and medical instrument.
However, until now this has been held back by the lack of commercial coherent radiation sources with necessary energy
parameters and efficiency. AgGa1-xInxSe2 and Hg1-xCdxGa2S4 are well-known middle IR crystal families introduced in
recent years. The main advantage of them is that their physical properties including refractive indices and birefringence
can be engineered by varying the contents of Ga, In, Cd and Hg. Consequently, the phase matching range can be
extended and the 90° non-critical phase matching in three-wave interaction can be realized within a certain wavelength
band. In consideration of influence of composition ratio, acceptable composition ratio and group velocity mismatch of
ultra-short pulses on nonlinear properties of AgGa1-xInxSe2 and Hg1-xCdxGa2S4 are investigated for the first time. The
corresponding phase-matching diagrams and spectral dependence of the acceptable composition ratio on wavelengths for
second harmonic generation and optical parametric oscillation pumped by the popular Nd3+:YAG (1.06 &mgr;m) and
Ho3+:ILF (2.08 &mgr;m) lasers are estimated and demonstrated with accounting of available Sellmeier coefficients. Group
velocity matching for second harmonic, optical parametric generation under the pump of the two lasers in AgGa1-xInxSe2
and Hg1-xCdxGa2S4 are carried out as well. All relative results are compared and analyzed within a number of sampling
values or continuum of composition ratios. In addition, the utilities of AgGa1-xInxSe2 and Hg1-xCdxGa2S4 for second
harmonic generation are also discussed finally.