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

Chinese Journal of Lasers 36 12 (2009) 3093– 3115

Zheng Kuang Dun Liu Walter Perrie Jian Cheng Shuo Shang S. P. Edwardson
 E. Fearon G. Dearden K. G. Watkins

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.