Generation of Radially Polarized Beam for Laser Micromachining

A novel means of generating radially polarized light is reported in this paper. A birefringent plate was placed in a divergent or divergent portion of the laser beam for polarisation conversation. The influence of birefringent plate thickness on the purity and efficiency of radial beam conversion is studied qualitatively. This technique is robust, simple and cost effective for radial polarisation conversion, and involvs only minimal optical components compared to alternative methods. Comparative analysis between linearly and radially polarized beams at different experimental condition is reported. Radially polarized beam increases the machining efficiency by 40-100% and reduces the focused spot size by more than 30%. Radially polarized beam finds wide application in semiconductor manufacturing. Application of radially polarized light for interconnect via drilling is demonstrated.