Continuous-wave laser damage mechanism of a spectral combining grating

Damage Characteristics of Aluminum-Coated Grating Irradiated by Nanosecond Pulsed Laser

An aluminum-coated grating (ACG) is a core component of laser systems and spectrometers. Understanding damage to the ACG induced by nanosecond lasers is critical for future high-power laser applications. In this study, we applied finite element simulation and practical experimentation to investigate the characteristics of ACG damage. Based on a coupling model using fluid heat transfer with the level-set method, we simulated the damage caused to an ACG by a 1064 nm nanosecond single pulse laser. The theoretical modeling showed that the ridge and bottom corners of the grid will be preferentially damaged, and the simulated damage threshold will range from 0.63 J/cm2 to 0.95 J/cm2. We performed a one-on-one damage test according to the ISO21254 standard to investigate the failure condition of 1800 l/mm ACGs; the laser-induced damage threshold (LIDT) was 0.63 J/cm2 (1064 nm, 6.5 ns). Microscopy images showed that the damaged area decreased with decreasing laser fluence, and scanning electron microscopy measurements showed that the main damage mechanism was thermodynamic damage, and that damage to the grid occurred first. The results of the experiments and simulations were in good agreement.