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Influence of Laser Beam Polarization on Micromachining of Crystalline Silicon Using Ultrafast Laser Pulses
R. Jagdheesh, A. Valarmathi and M. Sivakumar

Ultrafast laser machining is a unique technique to fabricate nano- and microscale structures with limited distortion to substrate materials. In the present work the influence of laser beam polarization direction on micromachining of crystalline Si with ultrafast laser pulses has been reported. The geometry of hole, ablation depth, machined features, kerf width and edge quality are studied with respect to the state of polarization. In terms of hole geometry, machining with S-polarized beam generates nearly circular holes as compared to asymmetrical stretching of the holes machined with P-polarization. Moreover, the depth of holes and channels machined with P-polarized beam is higher when compared to the depths of features machined with S-polarized beam. In multi-pulse, ultrafast laser machining, absorption of incident radiation is highly dependent on state of laser polarization and angle of incidence after first few pulses. The absorption is significantly higher for P-polarized beam resulting greater ablation depths. It is apparent from the experimental results that state of laser polarization is an important parameter in micromachining of semiconductors with ultrafast laser pulses under ambient condition.

Keywords: Femtosecond laser, laser micromachining, ultrafast laser pulses, polarization, silicon (Si)

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