Sensitive photothermal interferometric detection method for characterization of transparent plate samples

In this article, a recently developed, sensitive photothermal interferometric detection technique, in which an interference fringe pattern formed by overlapping two reflected probe beams from the front and rear surfaces of the sample was used to measure the photothermal signal, and its application for characterization of transparent (or partially transparent) plate samples were theoretically and experimentally investigated in detail. The theoretical descriptions of the intensity distribution of the interference fringe pattern and the photothermal signal with pulsed excitation were presented. Experiments were conducted with plate samples of optical glasses doped with heavy‐metal ions and the results were compared with the theoretical ones. Good agreement between theoretical and experimental results demonstrated the proposed photothermal interferometric detection technique to be a sensitive photothermal method for the study of the thermophysical properties of transparent samples. Its applicability to weak absorption or spectroscopy measurement and microvolume trace analysis was also discussed.