# Photoacoustic Spectroscopy-Based Detection for Identifying the Occurrence and Location of Laser-Induced Damage Using a Laser Doppler Vibrometer

## TL;DR

This paper introduces a new method using photoacoustic spectroscopy and a laser Doppler vibrometer to detect laser-induced damage in optical components in real time.

## Contribution

The novel PAS-LDV method enables non-contact, remote, and sensitive detection of laser-induced damage with practical applicability.

## Key findings

- The method achieved detection accuracy comparable to microscopy for various optical components and pulse durations.
- Vibration spectra matched natural modes predicted by finite element modeling, confirming the method's reliability.
- The technique remained effective under typical mounting conditions, showing its suitability for real-world use.

## Abstract

We present a photoacoustic spectroscopy (PAS)-based method using a laser Doppler vibrometer (LDV) for real-time detection of laser-induced damage (LID) in optical components. By measuring audible frequency surface vibrations, the method enables remote, non-contact, and sensitive detection. Experiments with various dielectric optics (slide glass and single-layer coatings) and pulse durations (7 ns and 360 ps) of an Nd:YAG laser (wavelength of 1064 nm) showed detection accuracy comparable to microscopy. Vibration spectra correlated with natural modes calculated by finite element modeling, and vibrations according to the detecting location were observed. The method remained effective under typical mounting conditions, demonstrating its practical applicability. This PAS-LDV approach offers a promising tool for in situ monitoring of LID in high-power laser systems.