Nanoscale confinement of energy deposition in glass by double ultrafast Bessel pulses

TL;DR

This paper demonstrates that double ultrafast Bessel pulses can significantly enhance nanochannel formation in glass by creating a long-living, highly absorbing state that confines energy deposition at the nanoscale.

Contribution

It reveals how double pulses separated by 10-500 ps improve nanochannel drilling efficiency through phase change and semi-metallization in glass.

Findings

Nanochannels with diameters down to 100 nm are achievable.

Double pulses increase energy confinement during drilling.

A long-living, highly absorbing state is induced, likely semi-metallization.

Abstract

Ultrafast laser pulses spatially shaped as Bessel beams in dielectrics create high aspect ratio plasma channels whose relaxation can lead to the formation of nanochannels. We report a strong enhancement of the nanochannel drilling efficiency with illumination by double pulses separated by a delay between 10 to 500 ps. This enables the formation of nanochannels with diameters down to 100 nm. Experimental absorption measurements demonstrate that the increase of drilling efficiency is due to an increase of the confinement of the energy deposition. Nanochannel formation corresponds to a drastic change in absorption of the second pulse demonstrating the occurrence of a phase change produced by the first pulse. This creates a highly absorbing long-living state. Our measurements show that it is compatible with the semi-metallization of warm dense glass which takes place within a timescale of <10 ps after the first laser pulse illumination.