Abstract
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 and 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.
Highlights
Transparent dielectrics are ubiquitous in modern technology, but their structuring at the nanometric scale is a difficult task
The mechanism leading to void channel formation in transparent dielectrics after the energy deposition stage is still an open question [14,15,16], our problematic here is that depending on the material and illumination geometry, limitations arise on the maximal and minimal nanochannel diameters that can be processed with Bessel beams
We have demonstrated that double pulse femtosecond illumination can drastically enhance the efficiency of nanochannel formation in comparison with the single pulse case
Summary
Transparent dielectrics are ubiquitous in modern technology, but their structuring at the nanometric scale is a difficult task. The mechanism leading to void channel formation in transparent dielectrics after the energy deposition stage is still an open question [14,15,16], our problematic here is that depending on the material and illumination geometry, limitations arise on the maximal and minimal nanochannel diameters that can be processed with Bessel beams. Increasing the pulse energy did not lead to an increase of the channel diameter above ∼300 nm, in contrast with a relatively similar glass, Corning 0211 where nanochannels could be processed with diameters from 200 to 800 nm [1] with a twice shorter Bessel beam length
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