Femtosecond laser ablation of chalcogenide glass: explosive formation of nano-fibres against thermo-capillary growth of micro-spheres

Abstract

Formation of nano-fibres ranging from 30 to 300 nm in diameter and exceeding the length of one millimetre was observed during explosive ablation of As2S3 glass by femtosecond pulses at high fluence (>5 J cm−2) irradiation of the 800 nm wavelength, 160 fs duration pulses in air. Spheres of up to several microns in diameter were also found to form, competing with nano-fibre formation and significantly deteriorating their morphology. Theoretical analysis of thermo-capillary and heat exchange mechanisms of the fibre formation predicts conditions under which the good nano-fibre morphology can be preserved.

Tipping solutions: emerging 3D nano-fabrication/ -imaging technologies

“…To push resolution limits to the nanoscale, advancements in lasers and optical microscopy were combined and evolved into microscale 3D fabrication techniques, where photons of a wavelength λ can be focused into a diffraction-limited spot size of ~λ/2, and controlled at timescales of a few femtoseconds. Such energy delivery has a broadly appreciated flexibility in energy deposition and reaches sub-wavelength structuring in 3D through several processes: formation of new phases of materials [12,13], precise ablation [14][15][16], and/ or polymerization [17,18]. More advanced laser fabrication methods can reach sub-micron resolution by exploiting nonlinear processes, such as multiphoton polymerization [19][20][21] and stimulated emission depletion techniques [22,23].…”

3D Microporous Scaffolds Manufactured via Combination of Fused Filament Fabrication and Direct Laser Writing Ablation

“…This is caused by surface tension, viscosity and temperature gradients of the thermo-polymer, as it is cast onto a previously deposited log. The contact points between old and freshly extruded logs creates cooling points with surface tension pulling a liquid polymer by surface tension gradient towards colder regions [48]. This is a similar effect to a so-called "repolymerization" observed in DLW lithography, were overexposed regions seem to self-form repetitive structures in 1D [49] and 2D [50] manners.…”

Laser trapping of deformable objects

“…The time scale of the molten glass's viscous flow can be estimated by τ f ≈ l 2 /ν, where l ∼ 1 µm is the characteristic size comparable with the waist of the beam and ν ≈ 10 −7 − 10 −6 m 2 /s is the kinematic viscosity of high temperature melts. Then, τ f ≈ 1 − 10 µs [22] is of the same order as the viscous response time of the "rigid" bubble. Hence, it is conceivable that the bubble's shape is modified before the bubble is pushed out.…”