Parallel femtosecond laser processing using intensity modulated diffraction pattern produced with spatial light modulator

Due to technical development of the adaptive optics, use of them in various laser processing applications has become possible. These techniques based on the adaptive optics have been applied with various lasers to generate diffraction patterns with equal intensity spots. In this paper ultrashort laser pulse ablation with intensity modulated diffraction pattern is presented. Diffraction patterns are generated with the Computer Generated Holograms (CGH) created using the Spatial Light Modulator (SLM). Applied CGHs are designed using method based on the Iterative Fourier Transform Algorithm (IFTA). Added to this Fresnel lenses are used to avoid problems with 0th-diffraction order. With this kind of designing procedure it is possible to generate diffraction patterns with intensity variation between diffracted spots. By intensity modulating the diffracted beams it is possible to ablate virtually arbitrary patterns with depth variation into the different materials. In this paper different kinds of CGHs are designed to generate various diffraction patterns with intensity modulation. These patterns are used to ablate greyscale images directly into the silicon using ultrashort pulses