Single-shot ultrafast laser processing of high-aspect-ratio nanochannels using elliptical Bessel beams

Abstract

Ultrafast lasers have revolutionized material processing, opening a wealth of new applications in many areas of science. A recent technology that allows the cleaving of transparent materials via non-ablative processes is based on focusing and translating a high-intensity laser beam within a material to induce a well-defined internal stress plane. This then enables material separation without debris generation. Here, we use a non-diffracting beam engineered to have a transverse elliptical spatial profile to generate high-aspect-ratio elliptical channels in glass of a dimension 350 nm×710 nm and subsequent cleaved surface uniformity at the sub-micron level.

Beam shaping for ultrafast materials processing

“…Although the transverse intensity profile of higher-order Bessel-like beams completely differ from the zero order version, the above mentioned remarkable properties of 11,37,38 Such intensity distributions/beam shaping approaches show promising prospects for material modifications and processing, e.g., the precise cutting of glass 11,35,39 by making targeted use of crack formations. 31,40 We verify excellent suitability of this class of beams for transparent materials processing using a time resolved tomographic imaging concept, see Bergner et al, 11 which allows to reconstruct the three-dimensional spatial distribution of the transient extinction coefficient κ (r). § This enables to directly measure the material's absorbing response ¶ caused by the ultrashort pulse and, thus, to analyze where energy was deposited.…”

High-resolution material structuring using ultrafast laser non-diffractive beams

“…Given the one-dimensional geometry of interaction, the relaxation of energy and the resulting material constraints occur radially, along the direction of the highest gradients, creating thus transverse forces of significant strengths. These features, and the resulting forces and stresses, are of interest when separation of matter is concerned and are thus becoming essential in large scale high-speed cutting and cleaving applications [57,58,64]. An example of glass cleaving operation [57] is given in Figure 2(a), emphasizing the scale and the quality of material separation.…”

“…In view of its optical and mechanical properties glass is a material of strong technical relevance for displays in consumer electronics or for medical devices, and glass cleaving and cutting operations have a clear market potential. Non-diffractive beams are particularly suited for glass (or in general dielectrics) separation technologies, as they can introduce hidden in-volume modifications (stealth machining) with large aspect ratios and stress fields orientations that facilitate separation [64]. In addition, creating asymmetries in the beam profile (e.g.…”

“…In addition, creating asymmetries in the beam profile (e.g. ellipticity, tilted fronts, or specific polarization [40,64] relative to material crystalline axes for crystalline dielectrics) can orient the resulting stress field to achieve maximum effect. This weakens the bonding strength on specific directions and leads to efficient separation with nondiffractive high aspect ratio beams that present asymmetric elongations along the transverse direction.…”

Axiparabola: a long-focal-depth, high-resolution mirror for broadband high-intensity lasers

“…Optical elements with long focal depths and narrow lateral widths are required for a variety of applications, such as material processing [1], optical guiding of microscopic particles [2], optical coherence tomography [3], and formation of plasma waveguides [4]. Conventional optical elements, such as spherical lenses and parabolic mirrors, cannot achieve the two goals simultaneously, since a long focal depth requires a low numerical aperture and a high lateral resolution requires a large numerical aperture.…”