Modeling and optimizing femtosecond laser process parameters for high-efficient and near damage-free micromachining of single-crystal GaN substrate

This paper presents a high-efficient and near damage-free micromachining method for gallium nitride (GaN) using femtosecond laser direct writing. To provide a precise selection principle of process parameters, the influences and interactions on GaN processing of parameters are systematically studied. Variance analysis results of single factor experiments show that laser power, scan speed, scan times and repetition frequency mainly influence the microgroove depth, microgroove width, heat-affected zone (HAZ) and material removal rate (MRR). In addition, the response surface method (RSM) indicates the interaction between scan times and repetition frequency has an appreciable influence on HAZ. And the interaction between scan speed and laser power plays a key role in MRR. Quadratic polynomial prediction models have been established by RSM and have discrepancies of less than 9.5% compared with the experimental results. The optimized parameters are important to achieve the desired control and high efficiency of femtosecond laser micromachining of single-crystal GaN substrate.