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Laser processing with ultra-short double pulses has gained attraction since the beginning of the 2000s. In the last decade, pulse bursts consisting of multiple pulses with a delay of several 10 ns and less found their way into the area of micromachining of metals, opening up completely new process regimes and allowing an increase in the structuring rates and surface quality of machined samples. Several physical effects such as shielding or re-deposition of material have led to a new understanding of the related machining strategies and processing regimes. Results of both experimental and numerical investigations are placed into context for different time scales during laser processing. This review is dedicated to the fundamental physical phenomena taking place during burst processing and their respective effects on machining results of metals in the ultra-short pulse regime for delays ranging from several 100 fs to several microseconds. Furthermore, technical applications based on these effects are reviewed.

An ultra-intense laser pulse interacting with a solid target can heat electrons to relativistic energies, driving the plasma to transparency before it expands into the classically underdense regime. This effect, called relativistic transparency (RT), has wide ranging significance across many lines of inquiry in relativistic laser–plasma interactions. Here, we show the temporal evolution of the relativistically induced transparency of a laser heated target as measured by a lower intensity probe beam, providing the first time-resolved measurement of the return to opacity in a target undergoing RT. We also measure a shift in the ellipticity angle of the probe polarization by up to 7.8 ∘ . Supporting 3D particle-in-cell simulations corroborate these measurements.

Under investigation in this paper is breathers and rogue waves on the plane wave/periodic background for the generalized complex short pulse equation. Firstly, the new Lax pair are obtained by means of a hodograph transformation, thereby enabling the construction of the generalized ( n , N - n ) -fold Darboux transformation. As applications, a number of different types of breathers and rogue waves have been observed in plane wave/periodic background, including loop breather, eye-shaped breather, four-petaled breather, kink-breather, loop bright rogue wave, loop dark rogue wave, eye-shaped rogue wave and line rogue wave. Specifically, these results represent a novel contribution to the study of the complex short pulse equation, and we categorize these results, as well as to delineate the precise conditions under which they are generated. Subsequently, the dynamic behavior of these solutions is illustrated in great detail through the use of a multitude of images. We hope our investigation can provide a contribution that will facilitate the generation of additional novel localized waves on various backgrounds.

This paper investigates the complex short pulse equation, which can govern the propagation of ultra-short pulse packets along optical fibers. From the known Lax pair of this equation, the generalized ( n , N - n ) -fold Darboux transformation is adopted to construct four types of position-controllable localized wave solutions, including loop rogue wave, loop semi-rational soliton, loop periodic wave and their mixed interaction structures, and graphical illustrations present these novel localized wave structures. It is shown that these localized wave solutions can become a loop shape due to hodograph transformation, which is different from other usual single-valued localized waves. Compared with the known results, the main highlight of this paper is not only to propose several new types of localized waves, but also to demonstrate how their positions can be controlled by particular parameters so that we can theoretically control them where we want them to appear; in particular, we derive some novel wave structures with diverse loop localized wave interaction phenomena. These exotic structures may enrich the understanding of the nature of loop rogue waves, which might help explain some physical phenomena in nonlinear optics.

The paper focuses on the dual high-power impulse magnetron sputtering of TiAlN coatings using short pulses of high power delivered to the target. The surface morphology, elemental composition, phase composition, hardness, wear resistance, and adhesive strength of TiAlN coatings with different Al contents were investigated on WC–Co substrates. The heat resistance of the TiAlN coating was determined with synchrotron X-ray diffraction. The hardness of the TiAlN coating with a low Al content ranged from 17 to 30 GPa, and its wear rate varied between 1.8∙10−6 and 4.9∙10−6 mm3·N−1·m−1 depending on the substrate bias voltage. The HF1–HF2 adhesion strength of the TiAlN coatings was evaluated with the Daimler–Benz Rockwell C test. The hardness and wear rate of the Ti0.61Al0.39N coating were 26.5 GPa and 5.2∙10−6 mm3·N−1·m−1, respectively. The annealing process at 700 °C considerably worsened the mechanical properties of the Ti0.94Al0.06N coating, in contrast to the Ti0.61Al0.39N coating, which manifested a high oxidation resistance at annealing temperatures of 940–950 °C.

The scattering of extremely short optical pulses propagating in a medium with carbon nanotubes containing a metallic inhomogeneity was studied. The behavior of a 3D pulse depending on three spatial coordinates and one temporal coordinate was examined. The electromagnetic field was considered based on Maxwell’s equations supplemented with a term that takes onto account the multiphoton absorption of carbon nanotubes. Features of the interaction of the pulse with a metal wire in the nonlinear medium under study were identified.

Under investigation is the complex space–time-shifted nonlocal short pulse equation, which is connected with the complex space–time-shifted nonlocal sine-Gordon equation through a covariant reciprocal transformation. The first and the second types of Darboux transformations with respect to N different purely imaginary spectrum and 2 N general complex spectrum are constructed by using loop group method, respectively. The generalized Darboux transformation corresponding to fixed number of purely imaginary spectrum with higher-order algebraic poles is proposed through limit technique. As an application, several kinds of analytical solutions including the bell-shaped loop soliton, higher-order loop soliton, breathing loop soliton and hybrid bell-shaped–breathing loop soliton solutions are obtained. It is found that the space–time-shifted parameters x 0 and t 0 can only have trivial effect of translations on the bell-shaped loop solitons, while they can produce nontrivial deformations for the breathing loop solitons. The singular solution traveling with certain space–time line is also given.

The paper deals with the (Cr1−xAlx)N coating containing 17 to 54 % Al which is deposited on AISI 430 stainless steel stationary substrates by short-pulse high-power dual magnetron sputtering of Al and Cr targets. The Al/Cr ratio in the coating depends on the substrate position relative to magnetrons. It is shown that the higher Al content in the (Cr1−xAlx)N coating improves its hardness from 17 to 28 GPa. Regardless of the Al content, the (Cr1−xAlx)N coating manifests a low wear rate, namely (4.1–7.8) × 10−9 and (3.9–5.3) × 10−7 mm3N−1m−1 in using metallic (100Cr6) and ceramic (Al2O3) counter bodies, respectively. In addition, this coating possesses the friction coefficient 0.4–0.7 and adhesive strength quality HF1 and HF2 indicating good interfacial adhesion according to the Daimler-Benz Rockwell-C adhesion test.

The paper studied the effect of high-voltage short-pulse electrohydraulic discharge (HVSPED) on the processes of catalytic cracking of oil sludge in order to increase the yield of light hydrocarbon fractions. A set of laboratory experiments was carried out varying the key parameters of HVSPED—discharge voltage, capacitance of capacitor banks and processing time. As a catalyst, the developed nanocomposite catalyst bentonite was used, with nickel packed. The optimal electrophysical parameters of oil sludge treatment by HVSPED were determined, providing the maximum yield of gasoline and kerosene fractions. The effectiveness of HVSPED treatment of oil sludge in the presence of a catalyst was confirmed by DTA–thermogravimetric analysis and chromatographic-mass spectral analysis of the light and middle fractions of the hydrogenate. The proposed approach made it possible to enhance the resource and energy efficiency of oil sludge processing using HVSPED, demonstrating high potential for further industrial application

Passive modelocking is the spontaneous self-organization of all light within a laser cavity that is initially disordered into a short pulse. The tutorial begins with a brief history, introduces the fundamental principles, and discusses modern modelocked lasers, and open questions.