Abstract
New measuring technique of the third-order elastic (TOE) constants in solids by using an optical Fabri-Perot interferometer has been developed. The amplitudes of fundamental ultrasonic waves and of induced second harmonic by lattice anharmonicity were measured through a change of the reflected intensity of laser light which is introduced by ultrasonic displacement. The valiles of six independent TOE constants were derived with the aid of valence-force field theory show good agreement with the previously reported values. It is shown that the secondary piezoelectric effects on TOE constants in GaAs would be negligible small. We have developed a new measuring method for the TOE constants by using an optical Fabri-Perot interferometer with which one can measure a small ultrasonic displacement of less than 10-3 8. The detailed experimental method, and the experimental results in germaniums and semi-insulating gallium arsenides are decribed in the following sections.
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