UV Ultrafast Laser Processing using Phase Masks

Abstract

Based on the combination of short pulse duration with short wavelength, UV ultrafast lasers provide unprecedented material processing quality. A high power UV ultrafast laser system comprises a Ti:sapphire front-end laser whose frequency tripled pulses are amplified in a UV excimer gain module. In this way, subpicosecond pulses are obtained at 248 nm with an average power of up to 10 W. Such pulses are ideally suited for the treatment of solid surfaces with sub-micron precision. A combination of diffractive optical masks with conventional imaging systems allows the generation of complex 2D structures with typical feature sizes of ∼ 200 nm on all materials including metals, semiconductors and dielectrics. A new technique for the fabrication of the phase masks or diffractive phase elements used in the experiments is based on excimer laser patterning of dielectric layers. Such phase masks feature a large processed area, high efficiency for VUV to NIR radiation and can be customized e.g. for perfect zero order suppression.