In-system optimization of hologram for holographic femtosecond laser processing

Abstract

We proposed a holographic laser processing system with the combination of femtosecond laser and the in-system optimization. Femtosecond laser processing that employ a computer-generated hologram (CGH) displayed on a liquid-crystal-on-silicon spatial light modulator (LCOS-SLM), called holographic femtosecond laser processing (HFLP). Due to the inherent aberrations of the actual optical system, the diffraction peaks of holographic femtosecond laser processing has non-uniformity. To overcome this problem, we demonstrated a method called in-system optimization that optimizing the uniformity of the diffraction peaks while conducting the laser processing simultaneously. By taking advantage of the rewritable capability of the LCOS-SLM, with finite times of iteration perform of the in-system optimization, we obtained uniform peaks of 0.96, when the maximum intensity at the peaks of the diffraction spots was normalized to 1.0. Make use of this system, we realized the high efficiency and uniformity of laser processing, and made compensation for part of the inherent aberration in the optical system. In particular, we believe it can not only effectively avoid the impact of environmental factors on the processing system and will greatly improve the processing efficiency and stability, in the meanwhile, it will be widely applied for precise laser processing in the future.