Light-sensitive surface-barrier generation of acoustic volume waves

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Abstract
A new method for generation and detection of acoustic volume waves in nonpiezoelectric dielectrics is described. The acoustic intensity is sensitive to band‐gap illumination. Acoustic conversion is observed on inserting the sample in a reentrant cavity, in contact with the center post during application of rf pulses. The induced conversion efficiency builds up with a time constant in the range of seconds to minutes depending on the nature of the metal dielectric contact and on rf pulse repetition rate. Acoustic signals of 75 dB above noise have been generated in KTaO3. Very long storage times are observed. A model for the transducer action based on induced space charge and a surface barrier is proposed, similar to the model of Fossheim and Bjerkan for surface‐wave generation in nonpiezoelectric dielectrics. The estimated electromechanical coupling coefficient is comparable to that of piezoelectric LiNbO3 and LiTaO3.