Volumetric Modification of Shaped and Dual Wavelength Ultrashort Laser Pulses in Fused Silica

Volumetric modification of transparent materials by femtosecond laser pulses is used for a wide range of applications. In this work, on the example of fused silica, it is shown experimentally and theoretically that in a certain range of energies the peak of absorption of laser radiation for doughnut-shaped pulses is several times larger than for Gaussian pulses. The experiments were performed with 1 ^st and 2 ^nd harmonics of the Astrella laser from Coherent. The effect of two different wavelength has also been investigated for single- to multiple-shot irradiation. We show that, due to radiation shielding by laser-generated free-electron plasma, the longer wavelengths are more advantageous for obtaining a more localized modification. This becomes very attractive for the purposes of material modification and laser writing processes.