A simple technique to overcome self-focusing, filamentation, supercontinuum generation, aberrations, depth dependence and waveguide interface roughness using fs laser processing

Abstract

Several detrimental effects limit the use of ultrafast lasers in multi-photon processing and the direct manufacture of integrated photonics devices, not least, dispersion, aberrations, depth dependence, undesirable ablation at a surface, limited depth of writing, nonlinear optical effects such as supercontinuum generation and filamentation due to Kerr self-focusing. We show that all these effects can be significantly reduced if not eliminated using two coherent, ultrafast laser-beams through a single lens - which we call the Dual-Beam technique. Simulations and experimental measurements at the focus are used to understand how the Dual-Beam technique can mitigate these problems. The high peak laser intensity is only formed at the aberration-free tightly localised focal spot, simultaneously, suppressing unwanted nonlinear side effects for any intensity or processing depth. Therefore, we believe this simple and innovative technique makes the fs laser capable of much more at even higher intensities than previously possible, allowing applications in multi-photon processing, bio-medical imaging, laser surgery of cells, tissue and in ophthalmology, along with laser writing of waveguides.

Nonlinear increase, invisibility, and sign inversion of a localized fs-laser-induced refractive index change in crystals and glasses

“…These invisible waveguidebased devices also have great potential in any see-through protection screen, such as car windshields, industrial displays, army helmets, and plane dashboards. The use of the multiscan technique or low repetition rates to avoid the heating effect 42 , and methods to minimize aberration such as using a spatial light modulator 43 or a dual-beam technique 44 in order to sharpen the Gaussian intensity profile should help obtain step refractive index inscriptions. Invisibility at specific wavelengths could enable interesting applications in photonic circuitry and gratings.…”

Transmembrane Facilitation of Lactate/H+ Instead of Lactic Acid Is Not a Question of Semantics but of Cell Viability

“…At the same time, the substrate affinity of the FNTs is in the double-digit millimolar range, i.e., channel-like low [ 7 , 8 ]. The FNT central transport path is shielded on either side by a constriction that is too narrow and too hydrophobic for a monocarboxylate anion to pass [ 15 , 16 , 17 ]. To overcome this barrier, the substrate is neutralized by protonation in the vestibule leading to the constriction, and subsequently the amino acid sidechains in the constriction region give way while the backbone remains in place [ 1 ].…”

Surface Probing of Ultra‐Short‐Pulse Laser Filament Cut Window Glass and the Impact on the Separation Behavior

“…The fundamental principle of the generation of elongated material modification within the bulk material is a currently discussed topic. [5][6][7][8][9][10] These linear modifications can be generated due to sensu stricto filamentation where Kerr effect occurs or due to elongated intensity distributions. The result of this study cannot bring further argument in this discussion.…”