Photoacoustic depth profiling of layered samples

A photoacoustic sensor for the indirect detection of acoustic waves on the basis of a prism was developed. This wide-band piezoelectric transducer allows temporal resolutions of better than nanoseconds, Owing to the finite acoustic velocity it is possible to distinguish between sound waves generated in different layers. Suitable samples were built up to estimate the depth profiling capabilities of the developed sensor. For a simple experiment the lower limit for the depth resolution in an aquatic system is about 30 mu m, corresponding to a temporal resolution of 20 ns. Only qualitative results were obtained with more complex layered samples.