ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

5pPAa1. Resonant photoacoustic measurements of optical absorption in solids.

Wei-li Lin

Dept. of Phys., Penn State Univ., University Park, PA 16802

For glasses and crystals the optical absorption near the infrared is much lower than that in the visible. While the previous noncontact resonant photoacoustic (PA) measurement is several orders of magnitude more sensitive than that of conventional PA in the visible for a piezoelectric sample, it was further developed to apply to nonpiezoelectric materials in the near infrared. The noncontact interdigital capacitor transducers were replaced by lithium niobate disks and PVDF films. By supporting the sample between transducers only at its corners, the quality factor has been improved and is comparable to that of a noncontact system, while the separate supports and the precise positioning of the sample are avoided. An optical absorption coefficient on the order of 10[sup -7] cm[sup -1] at 1.06 (mu)m has been measured with a 20 signal-to-noise ratio. Recent results on single crystals of quartz and calcium fluoride, using different piezoelectric transducers, will be discussed. [Work supported by NSF Grant No. DMR-9000549 and by the Office of Naval Research.]