| Autor: |
White, J. D., Yu, C., McKenna, M. J., Maynard, J. D. |
| Zdroj: |
Journal of the Acoustical Society of America; 1991, Vol. 89 Issue 4B, p1910-1911, 2p |
| Abstrakt: |
The photoacoustic effect is one of the most sensitive methods for measurements of the low optical absorption in glasses and crystals. Traditional methods using high-powered pulse lasers and attached piezoelectric transducers are limited by noise and scattered light at the transducer. Recently, a new resonant photoacoustic technique has been developed for highly transparent solids, where a cw laser modulated at the acoustic resonant frequency of the sample generates an acoustic signal amplified by the quality factor (Q) of the resonance. This technique is several orders of magnitude more sensitive than conventional pulse techniques. Noncontact capacitive transducers eliminate the problem of scattered light. Two different transduction mechanisms are important in the detection of the acoustic wave at the sample surface. First, the displacement of the surface of the dielectric sample in the electric field of the capacitor results in small changes in the capacitance. Second, through the piezoelectric effect, the strain generates a small electric field at the sample surface; here, the transducer acts as an rf receiver, detecting the changes in the electric field intensity. Based on recent measurments on single crystals of calcium fluoride and quartz, the relative contributions of these two mechanisms will be discussed. [Work supported by the Office of Naval Research.] [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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