Functional gradient films on aluminum alloy to improve its laser‐induced damage ability and reduce pollutant particles’ generation

Abstract

Laser‐induced damage on metal parts by stray light is a common issue for high‐energy laser systems, especially inertial‐confinement fusion (ICF) systems. Micro‐dust could be produced from the surface irradiated and adhere to and cause further damage of other optical parts like potassium dihydrogen phosphate (KDP) crystal. We propose a functional gradient film based on aluminum anodization to raise the laser‐induced damage threshold (LIDT). The number of particles produced by a 355‐nm nanosecond laser was considered a factor of LIDT. To investigate the interaction theoretically, a coupled model of electromagnetic radiation and heat conversion based on Ohm's law for a nanosecond laser pulse absorbed by the films was used to calculate the LIDT temperature. Films with different roughnesses and an untreated aluminum alloy (AA) were irradiated. The LIDT was 0.5 J/cm2, with a temperature of 5790 K, which largely prevented the laser damage of the AA and reduced particles produced while metal damaged. The combination of simulations and experiments provided a new and simple indication of LIDT for aluminum‐based functional gradient films. It also provided a guide for clean manufacturing with less particle generation, which is vital to the success of ICF systems that will generate sustainable energy.