Anomalous acoustooptic effects in glass and acrylic plastics
Anomalous acoustooptic effects are observed when a laser beam is guided into an acrylic plastic or glass plate and is modulated by acoustic waves generated by electrodynamic or piezoelectric transducers. The laser beam spreads into various beams with the modulating frequency, the double frequency and the triple frequency, simultaneously. Also, the observed photodetected current showed phase shift in audio signals depending on the location of the photodetector. The component of elliptical polarization showed modulation frequency sensitive transmission in glass. It is found that though the amount of transmitted light is minimum at the cross-polarization condition, the lightwave power transmission coefficient is maximum at this same condition. These lightwave transmission coefficients show modulation frequency dependency. Analogous phenomena have also been observed in cylindrical configurations, such as in a glass rod, and an optical fiber. A theoretical explanation of the anomalous effects has been attempted in this work. Although, a large volume of the sample would be required, the Raman and Nath assumptions for progressive waves, and standing waves using a first-order modulation of the index of refraction by the acoustic wave frequency, are assumed here also. However, a different approach is used by the author to derive the lightwave transmission equations. The author assumes cases where a second-order modulation of the index of refraction by the acoustic signal could be possible, and also a spatial dependency of the magnitude of the index of refraction by the acoustic modulating frequency.
"Anomalous acoustooptic effects in glass and acrylic plastics"
(January 1, 1992).
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