Diffractive Multi-Beam Ultra-fast Laser Micro-processing using a Spatial Light Modulator

Multi-beam ultra-fast laser parallel micro-processing using spatial light modulation is demonstrated in this paper. Diffractive multi-beam patterns are generated with a spatial light modulator (SLM),which is driven by computer generated holograms (CGHs). The CGHs calculated by appropriate algorithms are displayed on the SLM to split an input laser beam to a number of beamlets and digitally manipulate their positions and intensity. The undesired damage by the energetic zero order beam can be avoided by either installing a 4f optical system to block the zero order at the Fourier plane or adding a Fresnel zone lens on the CGH to defocus the zero order at the processing plane. The surface ablation of materials using multi-beam patterns synchronised with a scanning galvanometer system shows flexible and high throughput parallel processing. By tightly focusing the diffractive beams with an objective into transparent materials, high speed dynamic femto-second laser two-dimensional (2D) and three-dimensional (3D) internal structuring is also presented. The results demonstrate the high precision micro-processing with higher efficiency, showing the potential for ultra-fast laser parallel processing in real industrial applications.