Nonlinear optical coefficients of Hg-based superlattices

The first measurement of the third-order nonlinear optical susceptibility χ(3) in Hg-based narrow-gap semiconductor superlattices is reported. Four-wave mixing experiments were performed at CO2 laser wavelengths on a series of HgTe/CdTe and Hg1−xZnxTe/CdTe superlattices whose energy band gaps are approximately zero at T=0 K. The nonlinearity is believed to due to modulation of the free-carrier temperature and density by the optical beams. Theoretical estimates of the third-order nonlinear susceptibility due to this mechanism are in good agreement with the experimental results.