Sensitivity enhancement of surface thermal lens technique with a short-wavelength probe beam: Experiment

Abstract

Surface thermal lens is a highly sensitive photothermal technique to measure low absorption losses of various solid materials. In such applications, the sensitivity of surface thermal lens is a key parameter for measuring extremely low absorption. In this paper, we experimentally investigated the influence of probe beam wavelength on the sensitivity of surface thermal lens for measuring the low absorptance of optical laser components. Three probe lasers with wavelength 375 nm, 633 nm, and 1570 nm were used, respectively, to detect the surface thermal lens amplitude of a highly reflective coating sample excited by a cw modulated Gaussian beam at 1064 nm. The experimental results showed that the maximum amplitude of surface thermal lens signal obtained at corresponding optimized detection distance was inversely proportional to the wavelength of the probe beam, as predicted by previous theoretical model. The sensitivity of surface thermal lens could, therefore, be improved by detecting surface thermal lens signal with a short-wavelength probe beam.

Robust Optical Physical Unclonable Function Based on Total Internal Reflection for Portable Authentication

“…The high stability of silica is especially relevant in high-power laser applications, where materials based on silica are predominantly selected for the most critical components. The performance of such components is highly sensitive to subsurface defects, which often serve as the main catalysts for catastrophic laser-induced damage. , Currently, nondestructive characterization of subsurface defects predominantly depends on weak absorption testing and total internal reflection microscopy. − The latter is widely known as a cost-effective and rapid diagnostic approach. The randomly distributed subsurface defects, which arise during the polishing process, could serve as potential entropy sources for PUFs.…”