Elastic,optical and nonlinear optical properties of InPS4

Indium phosphorus sulfide, a promising nonlinear optical material, is investigated with respect to elastic constants, anisotropic sound velocity, absorption, refraction and nonlinear optical applications. The elastic tensor components are evaluated from phonon frequency and wavevector data obtained by Brillouin scattering. The ordinary and extraordinary dispersion is determined for the entire transparency range (0.4–8 μm). A 5-parameter Sellmeier equation is fitted to these data and is used to calculate phase matching diagrams for second-harmonic generation and general three-frequency mixing. A possible, attractive application, angle tuned parametric oscillation, is discussed.