Optical nonlinearity in mercury telluride

Mercury telluride is shown to have the largest known third-order nonlinear optic susceptibility with response time in the picosecond range. At 10.6 μm and T=300 K, χ(3)=1.6×10−4 esu. The response time, estimated from the dispersion of χ(3), is 5 ps. The effect is attributed to interband population modulation. It does not saturate below 1 MW/cm2.