Laser pretreatment enhances the laser-induced damage threshold of MgAl₂O₄ transparent ceramics

The demand for transparent ceramics as essential optical components in high-energy laser systems is escalating. Given the continuous surge in laser output power, there is an urgent need to enhance their laser-induced damage threshold (LIDT). This research systematically investigates the influence of variables such as laser energy density, number of scan repetitions, and stepwise scanning on the LIDT of MgAl 2 O 4 transparent ceramics by modulating the process parameters of laser pretreatment. Through this method, oxygen vacancy defects on the material surface were effectively minimized, achieving surface purification of transparent ceramics and reducing residual stress. Under a consistent laser energy density of 8.96 J/cm 2 , the transparent ceramics were subjected to 1 to 9 scanning passes. The LIDT showed a progressive increase with the number of scans, reaching a maximum value of 15.0 J/cm 2 after seven scans, which corresponds to a 34% improvement compared to untreated samples. Additionally, laser pretreatment facilitated the expansion of the material's bandgap and increased transmittance in the 200-300 nm band, further substantiating the intimate relationship between the reduction of oxygen vacancy defects and the improvement of optical properties. The findings indicate that laser pretreatment, as an effective post-processing technique, can substantially augment its resistance to laser damage by optimizing the microstructure and surface characteristics of the material. Moreover, judicious control of laser energy density and number of scan repetitions is crucial for optimally improving LIDT. In conclusion, this study offers what we believe to be a new theoretical foundation and technical support for the performance optimization of transparent ceramics in high-power laser systems, underscoring the significant potential of laser pretreatment as an effective post-processing technology in enhancing material optical properties and durability.