Abstract

The sensitivity of photothermal detection relies on both the magnitude of the response of a sample to excitation and the way the response is sensed. We propose a highly sensitive photothermal interferometry by addressing the above two issues. One is the use of moving excitation to enable a different manner in sample heating and cooling, which results in a strong thermoelastic response of the sample. The other is the use of a balanced Mach–Zehnder interferometer with a defocused probe beam to sense the complex response induced by the phase delays taking place at the sample surface and in the surrounding air. The method was verified experimentally with a Nd-doped glass to have 68-fold sensitivity enhancement over the classical photothermal common-path interferometry.

© 2021 Optical Society of America

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