Photoacoustic effect in piezoelectric ceramics

Audiofrequency signals produced by the absorption of chopped light in silvered piezoelectric ceramic discs have been measured as a function of chopping frequency, optical wavelength, optical power, transducer size, and size of illuminated area. The results show that the detected signal varies inversely as ω, is not strongly wavelength dependent in the 0.45–3.4-μm range, is linearly dependent on optical power up to at least 100 mW, is larger for smaller discs, and is approximately independent of the illuminated area for a given disc. A one-dimensional theoretical model of the photoacoustic effect in terms of the various hybrid stress, electric, and thermal material parameters is compared with the experimental results; the principal features of the data are explained by the model. The importance of the photoacoustic signal generated in the transducer to photoacoustic spectroscopy of transparent solids is discussed.