The role of light-induced nanostructures in femtosecond laser micromachining with vector and scalar pulses.

In this article we compare the results of micromachining of fused silica and silicon with tightly focused scalar (viz., circularly and linearly polarized) and vector (viz., azimuthally and radially polarized) femtosecond laser pulses. We show that drilling with radially polarized pulses produces holes with smoother and better-delineated walls compared with the other polarizations used, whereas linearly polarized pulses can machine 20-nm wide single grooves in fused silica when the electric field of the pulse is aligned perpendicular to the cutting direction. The observed polarization-controlled micromachining is due to the formation of sub-diffraction-limited nanostructures that are optically produced in the multi-pulse irradiation regime.