Improved efficiency for processing transparent materials by using double-pulse explosion drilling

Recent years have seen an increase in the demand of laser processing of transparent materials because of the numerous applications, such as the formation of through-silicon vias, glass scribing, the creation of optical wave guides, and so on. Furthermore, laser processing is expected to be used for fabricating photonic devices and circuits. Although significant research efforts have focused on laser processing of transparent materials, many unexplained mechanisms remain to be elucidated. In particular, mechanisms that remain unclear include plasma absorption and the process whereby traces expand when using double pulses. In 2017, to improve the laser-processing speed and efficiency, we proposed a method for cutting transparent materials called the “double-pulse explosion drilling method,” which uses two laser pulses of differing wavelengths to create internal modifications in a material. In the present study, we use the double-pulse method to drill through transparent materials and investigate how the second pulse affects laser-beam absorption and the generation of processing traces. We used a picosecond laser with pulses at 532 and 1064 nm for the first and second pulse, respectively. The target material was fused silica glass. The results clarify how the use of double pulses improves the processing efficiency. This presentation gives the experimental results and discusses the processing mechanisms at work in the double-pulse method.