Determination of nonlinear (quadratic) optical susceptibility of GaAs and GaP from electro-optic measurements

The nonlinear optical susceptibility χ₂₃₁ was determined from the results of electro-optic measurements. Special attention was paid to possible systematic errors arising in the measurement of the induced birefringence and hindering correct interpretation of the electro-optic spectra. The dispersion law was determined and it was used to find the contributions of electrons in the lattice to the nonlinear refractive index. A comparison of the experimental conditions in second-harmonic generation and electro-optic measurements yielded a calculation formula for the nonlinear (quadratic) susceptibility χ₂₃₁ of GaAs and GaP. The calculated results were in good agreement with the theory and experiments involving optical harmonic generation. The threshold of the singularity partly responsible for the nonlinear (quadratic) susceptibility was determined for gallium arsenide.