Dispersion of nonlinear optical susceptibility in GaAs and GaSb

Abstract

Dispersion measurements of the nonlinear optical susceptibility (NLOS) of GaAs and GaSb crystals are reported. The intensity of the second-harmonic beam generated in the III-V crystal was measured as a function of the frequenvy (1.2-1.8 eV) of the radiation source. This measurement was simultaneously calibrated with respect to the second-harmonic beam generated in a reference quartz crystal. The NLOS modulus was determined from the ratio of the signals in the III-V crystal and the quartz. The dispersion measurements were carried out on mechanically polished crystals. Test measurements on etched crystals, at a few energy values, showed a change in the magnitude of the NLOS, although no significant influence on the spectral shape was found. The structure of the spectra shows good correspondence between the position of the measured peaks and the position of those peaks found in the single-photon (linear) measurements. Previous measurements in GaAs show no such correspondence. Some evidence was found for the possible existence of a two-photon double-resonance transition in GaSb. The Miller-cofficient spectra were calculated. For GaAs the spectrum was found to be approximately constant. For GaSb no pronounced structures were found.