Single-shot high aspect ratio bulk nanostructuring of fused silica using chirp-controlled ultrafast laser Bessel beams

Abstract

International audienceWe report single-shot, high aspect ratio nanovoid fabrication in bulk fused silica using zeroth order chirp-controlled ultrafast laser Bessel beams. We identify a unique laser pulse length and energy dependence of the physical characteristics of machined structures over which nanovoids of diameter in the range 200-400 nm and aspect ratios exceeding 1000 can be fabricated. A mechanism based on the axial energy deposition of nonlinear ultrashort Bessel beams and subsequent material densification or rarefaction in fused silica is proposed, intricating the non-diffractive nature with the diffusing character of laser-generated free carriers. Fluid flow through nanochannel is also demonstrate

Limitations to laser machining of silicon using femtosecond micro-Bessel beams in the infrared

“…For glass, we confirm that this pulse energy allows complete through hole modification when the focus is appropriately positioned. 10,26,27 This is of great importance for technological considerations, especially when ablation along the channel is achieved. It offers the possibility for direct microchannel drilling 10,28 and ultrahigh precision cutting of transparent dielectrics.…”

[INVITED] Ultrafast laser micro-processing of transparent material

“…This does not allow full exploitation of the three-dimensional capabilities of ultrafast laser micromachining. To overcome the limitations, an application of non-diffractive Bessel beams for laser material processing has been attempted [105][106][107][108][109][110][111][112][113][114]. The intensity maximum is strongly localized over a distance that exceeds the Rayleigh range of Gaussian beams by orders of magnitudes.…”

“…In glass, modifications or damage tracks are found to be over longer distances [106]. The applications include the surface ablation [107,108], channel formation [109,110], writing waveguides [111] and gratings [112] within bulk glasses, and cutting of glass [113]. …”

Plasma absorption evidence via chirped pulse spectral transmission measurements

“…Note that this choice allows us to have negligible non-linear Kerr effects associated with the light-matter interaction under study and to take advantage of the electron avalanche ionization 14 for an efficient laser energy deposition into the bulk, as also confirmed by the previous glass microfabrication results obtained by means of Bessel beams in the picosecond regime. 15,16 The laser beam size is reduced by a two-sphericalmirrors telescopic system (not shown in Fig. 1) and sent through an axicon with 178 apex angle for the generation of a Bessel beam (truly a Bessel-Gauss beam).…”