PHOTOTHERMAL MEASUREMENTS WITH A JAMIN INTERFEROMETER

We present a numerical study of the behavior of the signal in a photot hermal experiment combining the mirage effect and a Jamin interferomet er. Our analysis is limited to a square-pulse excitation by at weakly absorbed Gaussian pump laser beam with a large radius. We investigate the influence of three parameters: the time of illumination of the sam ple, the time of extinction of the pump beam, and the height of the pr obe-beam arm of the Jamin interferometer above the sample. We show tha t the path. difference, which induces the variation of intensity at th e output of the Jamin interferometer, is caused by both probe-beam def lection and temperature variation of the refractive index of air above the sample. The first effect is dominant for short times, and interfe rometry is a sensitive tool to monitor it. (C) 1997 Optical Society of America.