HARMONIC GENERATION OF MICROWAVE PHONONS.
Physical sciences research papers no. 369,
AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS
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Harmonic generation due to the phonon-phonon interaction and harmonic generation in nonpiezoelectric dielectrics produced by the radiation pressure of a microwave electric field was investigated. Harmonic generation due to the phonon-phonon interaction was measured by detecting the 9-GHz second-harmonic component of acoustic waves, whose fundamental was generated by the piezoelectric effect in a 4.5-GHz reentrant cavity, and was treated theoretically by obtaining perturbation solutions for both the classical nonlinear wave equation and the quantum-mechanical phonon-phonon interaction in which two collinear phonons collide to create a third phonon. The third-order elastic coefficients c sub 111 and c sub 333 have been measured for quartz, sapphire, and MgO. The second harmonic of longitudinal waves in MgO was observed to be of the same magnitude as the fundamental for an acoustic power of 100 mWsq cm strain 0.000001. Harmonic generation due to radiation pressure was measured by detecting the 9-GHz acoustic waves harmonically generated at the end surface of a nonpiezoelectric rod placed in the electric field of a 4.5-GHz cavity. The radiation pressure of Maxwell - Faraday stress was computed from the measured value of the electric field and used to predict the acoustic power generated. A new perturbation method was developed for measuring this electric field, which is as large as 0.00001 Vcm. Author
- Solid State Physics