Influence of polarization on the hole formation with picosecond laser

Linear polarization effects on laser drilling were investigated by the use of a picosecond laser system. It was observed that the exit shapes of stainless steel were placed perpendicular to the direction of polarization. According to theoretical analysis, the main factor that determines the exit hole shape is the difference between R_s and R_p. When this gap is large enough, the bulges on the exit hole will be easily observed. Inversely, when the gap is small, bulges can be barely spotted on the exit hole. This is further confirmed by comparative experiment and calculation conducted on a copper sheet.