Tubular filamentation for laser material processing

Abstract

An open challenge in the important field of femtosecond laser material processing is the controlled internal structuring of dielectric materials. Although the availability of high energy high repetition rate femtosecond lasers has led to many advances in this field, writing structures within transparent dielectrics at intensities exceeding 1013 W/cm2 has remained difficult as it is associated with significant nonlinear spatial distortion. This letter reports the existence of a new propagation regime for femtosecond pulses at high power that overcomes this challenge, associated with the generation of a hollow uniform and intense light tube that remains propagation invariant even at intensities associated with dense plasma formation. This regime is seeded from higher order nondiffracting Bessel beams, which carry an optical vortex charge. Numerical simulations are quantitatively confirmed by experiments where a novel experimental approach allows direct imaging of the 3D fluence distribution within transparent solids. We also analyze the transitions to other propagation regimes in near and far fields. We demonstrate how the generation of plasma in this tubular geometry can lead to applications in ultrafast laser material processing in terms of single shot index writing, and discuss how it opens important perspectives for material compression and filamentation guiding in atmosphere.

Optical vortex trapping and annihilation by means of nonlinear Bessel beams in nonlinear absorbing media

“…Regarding the practical generation of NBBs, they are excited by linear Bessel beams introduced in the nonlinear medium [19][20][21][22][25][26][27]. The linear Bessel beam u = b B J m √ 2ρ exp(imϕ) reshapes into the NBB characterized by the same cone angle, topological charge m and with inward Hänkel beam amplitude |b in | equal to b B [20,28].…”

Light trajectory in Bessel–Gauss vortex beams

“…1(a) and 2. The nondiffracting property has been further employed in many applications, such as nonlinear filamentation control [10][11][12][13][14][15], laser machining [16][17][18], and particle trapping and guiding [19].…”

Control of spatial four-wave-mixing efficiency in Bessel beams using longitudinal intensity shaping

“…This has been shown to yield significant improvement in controlling energy deposition, and has been the subject of intense interest for generating long and uniform plasma channels [2][3][4] and creating high aspect ratio structures in micro-and nano-machining applications [5][6][7][8][9]. The application of Bessel beams in laser processing and filamentation has also been demonstrated for Bessel vortices [10].…”