Study on effective cleaning of gold layer from fused silica mirrors using nanosecond-pulsed Nd:YAG laser

A study on effective laser cleaning of gold layer deposited on fused silica substrates used in beamlines of synchrotron radiation (SR) sources using nanosecond-pulsed Nd:YAG laser has been carried out. The influence of pulse duration, beam incidence angle, spot overlapping, laser fluence, and number of passes on cleaning efficiency has been investigated. An approximately 48 nm thick gold layer from a mirror surface area of ~48 cm2 has been cleaned in 3 min. Laser clean quality and efficiency has been analyzed using microscope, scanning electron microscope (SEM), and angle-dependent reflectivity measurement techniques using SR beamline. Optimization of cleaning parameters resulted in a cleaning efficiency of ~98%. This study provides an alternate and low-cost solution for reuse of gold-coated, damaged mirrors.