OPTICAL THIRD ORDER MIXING IN GaAs, Ge, Si, AND InAs.
HARVARD UNIV CAMBRIDGE MASS DIV OF ENGINEERING AND APPLIED PHYSICS
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Nonlinear optical difference mixing of CO2 laser radiation is studied in the semiconductors GaAs, Ge, Si, and InAs. The fourth-rank electric susceptibility tensor receives independent contributions from the bound or valence electrons, chi superscript b, and, in n-type material from the conduction electrons, chi superscript n. These two contributions are separated and measured in GaAs. Chi superscript b is found to be anisotropic and chi superscript n is isotropic for carrier concentrations n or 5 x 10 to the 16th powercc. The relative signs of the susceptibilities are determined. Chi superscript b in Ge and GaAs, and chi superscript n in GaAs and InAs all have the same sign for the particular frequency combination studied. Theoretical and experimental evidence indicate that this sign is positive. At room temperature chi superscript n in GaAs in a linear function of n for n or 5 x 10 to the 16th powercc. The value of the slope, the partial derivative of chi superscript n with respect to n, is a direct measure of the nonparabolicity of the conduction band in GaAs. It is shown to be inconsistent with Kanes model for small direct band gap semiconductors, and in agreement with Cardonas indirect measurements of the nonparabolicity in GaAs. Author
- Solid State Physics