Enhancement of ultrashort laser pulses absorption in glass using single MHz burst

In this study, the effects of burst mode on the absorption of ultrashort laser pulses in glass are investigated. The material modifications induced by single pulses and by single bursts with the same energy are observed in optical transmission microscopy. 40 µJ bursts with different numbers of pulses are considered. Our results demonstrate that distributing energy over multiple pulses in a burst (with an intra-burst frequency of 40 MHz) significantly enhances the material modification. Optical microscopy confirms that burst mode modifications produce material alterations whereas a single-pulse irradiation does not. There is an optimal pulse number after what the modifications decrease. We show how a glass-to-glass welding can be achieved in burst mode with an energy for which it is not possible using a single pulse. These findings highlight the potential of burst mode to improve laser processing of transparent materials using less power.