Enhanced photothermal displacement spectroscopy for thin-film characterization using a Fabry-Perot resonator

TL;DR

This paper introduces a highly sensitive photothermal displacement spectroscopy method using a Fabry-Perot resonator to improve thin-film characterization, achieving significant enhancement over traditional techniques.

Contribution

The paper presents a novel technique that leverages a Fabry-Perot resonator to significantly boost the sensitivity of photothermal displacement spectroscopy for thin films.

Findings

Enhanced sensitivity proportional to the square of the cavity finesse.

Successful measurement of thermal properties of multilayer dielectric mirrors.

Potential for improved thin-film characterization in various applications.

Abstract

We have developed a new technique for photothermal displacement spectroscopy that is potentially orders of magnitude more sensitive than conventional methods. We use a single Fabry-Perot resonator to enhance both the intensity of the pump beam and the sensitivity of the probe beam. The result is an enhancement of the response of the instrument by a factor proportional to the square of the finesse of the cavity over conventional interferometric measurements. In this paper we present a description of the technique, and we discuss how the properties of thin films can be deduced from the photothermal response. As an example of the technique, we report a measurement of the thermal properties of a multilayer dielectric mirror similar to those used in interferometric gravitational wave detectors.