Super-efficient drilling of metals with ultrafast non diffractive laser beams

Abstract

A highly efficient drilling process is found in non-transparent metallic materials enabled by the use of non-diffractive ultrafast Bessel beams. Applied for deep drilling through a 200 μm-thick steel plate, the Bessel beam demonstrates twofold higher drilling efficiency compared to a Gaussian beam of similar fluence and spot size. Notwithstanding that surface ablation occurs with the same efficiency for both beams, the drilling booster results from a self-replication and reconstruction of the beam along the axis, driven by internal reflections within the crater at quasi-grazing incidence, bypassing potential obstacles. The mechanism is the consequence of an oblique wavevectors geometry with low angular dispersion and generates a propagation length beyond the projection range allowed by the geometry of the channel. With only the main lobe being selected by the channel entrance, side-wall reflection determines the refolding of the lobe on the axis, enhancing and replicating the beam multiple times inside the channel. The process is critically assisted by the reduction of particle shielding enabled by the intrinsic self-healing of the Bessel beam. Thus the drilling process is sustained in a way which is uniquely different from that of the conventional Gaussian beam, the latter being damped within its Rayleigh range. These mechanisms are supported and quantified by Finite Difference Time Domain calculations of the beam propagation. The results show key advantages for the quest towards efficient laser drilling and fabrication processes.

Supercontinuum Induced by Filamentation of Bessel-Gaussian and Laguerre-Gaussian Beams in Water

“…These special properties make vortex beams widely applied in optical tweezers [7][8][9][10][11][12][13], optical imaging [14][15][16], information transmission and cryptography [17][18][19][20][21][22] and microprocessing [23][24][25][26] and other fields. For example, Bessel beams have propagation invariance compared with Gaussian ones; that is, they have the ability to maintain their shape and peak power at the extended focal region (Bessel region), which makes them have promising application prospects in many fields, especially for micro-processing.…”

Picosecond Bessel Beam Fabricated Pure, Gold-Coated Silver Nanostructures for Trace-Level Sensing of Multiple Explosives and Hazardous Molecules

“…Laser ablation of a silver substrate in ambient air and under the influence of picosecond Bessel beam profile was carried out for the first time, to the best of our knowledge. Earlier experiments emphasized the advantages of BB ablation over conventionally employed Gaussian beam [91]. The BB profile induced single spot ablation imprint on Ag as well as the variation of its central lobe region have been thoroughly explored.…”

Ultra-high-aspect-ratio structures through silicon using infrared laser pulses focused with axicon-lens doublets

“…The simulations are performed based on a numerical model using the Fresnel transfer function method as described in references [39,40]. For valid calculations under the paraxial approximation, we consider here an input collimated Gaussian beam of beam-waist 𝜔 0 = 2.4 mm and wavelength 𝜆 = 1550 nm illuminating the axiconlens doublet (at 𝑧 = 0) including a lens with focal length 𝑓 = 400 mm.…”