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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.

The short pulse equation is an important integrable equation in nonlinear optical fibers, which describes the propagation of ultra-short optical pulses in nonlinear media. Popowicz proposed the matrix short pulse equation and obtained four-component version of the short pulse-type equation in 2017. This paper focuses on constructing the binary Darboux transformation for the focusing–focusing, focusing–defocusing and defocusing–defocusing coupled modified complex short pulse (cm-CSP) equation, which can be reduced from the 2 × 2 matrix short pulse equation. By using a hodograph transformation, the cm-CSP equation converts to a coupled modified complex integrable dispersionless equation. Through the Darboux transformation, we derived bright–bright soliton, bright–dark soliton solutions, periodic-like solutions, rational solution and mixed solution (rational soliton) for the cm-CSP equation with vanishing and non-vanishing backgrounds. These solutions can be divided into smooth, cuspon and loop type. Some properties and asymptotic behavior of soliton solutions are analyzed. We must emphasize that compared with the traditional Darboux transformation, the binary Darboux transformation in this paper has the merits that the dark soliton and rational solution of the equation can be obtained more efficiently. Compared with the single-component modified CSP equation, the properties of the cm-CSP equation are more abundant, such as the fact that the cm-CSP equation has bright soliton and dark soliton solutions simultaneously. Compared with the focusing–focusing cm-CSP equation, the focusing–defocusing and defocusing–defocusing equation has some different properties, such as the existence of singular periodic-like solutions. We also emphasize that the asymptotic analysis of the collision solutions of the cm-CSP equation under the nonzero background has not been reported in other literature.

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.

Background: Despite extensive research, there is still no consensus on the optimal treatment for Striae distensae (SD). Aim: To evaluate the efficacy of ablative (short pulse (SP) mode) versus combined ablative and non-ablative (short pulse + smooth (SP + SM) mode) modality of Er: YAG laser for the treatment of SD. Methods: This prospective study was conducted on 29 female participants with SD referred to Razi Hospital in 2021. The body areas were divided into left and right side areas. The right side of body areas with SD was treated with SP + SM mode. The left side of body areas with SD was only treated with SP mode. Three months after treatment, clinical improvement was assessed based on dermatologist assessment and patients’ opinion. Results: The participants were middle-aged women with SD on the chest, abdomen, thighs, knees, or arms. SD in both study groups (SP + SM mode versus SP mode alone) showed improvement after treatment. Nonetheless, there was no statistically significant difference between the two study groups regarding the clinical improvement based on dermatologist assessment ( p  = 0.279) and improvement of striae based on patient opinion ( p  = 0.208). Conclusion: In conclusion, we demonstrated that both ablative (SP mode) and combined ablative and non-ablative (SP + SM mode) strategies of Er: YAG laser are efficient for the treatment of SD. However, we failed to show any superiority for combined ablative and non-ablative (SP + SM mode) compared to ablative (SP mode) modality.

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 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.