High-energy bow tie multi-pass cells for nonlinear spectral broadening applications

Multi-pass cells have emerged as very attractive tools for spectral broadening and post-compression applications. We discuss pulse energy limitations of standard multi-pass cells considering basic geometrical scaling principles and introduce a novel energy scaling method using a multi-pass cell arranged in a bow tie geometry. Employing nonlinear pulse propagation simulations, we numerically demonstrate the compression of 125mJ, 1 ps pulses to 50 fs using a compact 2 m long setup and outline routes to extend our approach into the Joule-regime.

A Compact Accelerator-Based Light Source for High-Power, Full-Bandwidth Tunable Coherent THz Generation

Terahertz (THz) radiation sources are increasingly significant for many scientific frontiers, while the generation of THz radiation with high-power at wide-tunable frequencies is still a limitation for most existing methods. In this paper, a compact accelerator-based light source is proposed to produce coherent THz radiation with high pulse energy and tunable frequency from 0.1 THz to 60 THz. By using a frequency beating laser-modulated electron beam and undulator taper, intense coherent THz radiation can be generated through undulators. Theoretical analysis and numerical simulations demonstrate that the proposed technique can generate narrow-bandwidth THz radiation with a pulse energy up to 6.3 millijoule (mJ) and the three-dimensional effects of beam has limited influence on its performance. The proposed technique will open up new opportunities for THz spectroscopic and time-resolved experiments.

Influence of laser processing conditions on the depth and microhardness of layers formed on titanium

In this work, we studied the depth and microhardness of the layers formed on titanium during laser processing in a graphite environment. The energy and duration of the laser pulse varied from 0.76 to 10.17 J and from 0.5 to 3 ms, respectively. As a result of processing, the formation of layers characterized by a depth of 8.3-800 μm and a microhardness of 9.68-28.01 GPa took place. Regression models are constructed that describe the effect of laser processing conditions on the indicated characteristics of the layers. It was found that the pulse energy had the greatest effect on the depth and microhardness of hardened titanium.

Wear resistance discrete management of formative tool

The article is devoted to the organization of management of the application of wear-resistant materials on the formative tool at set intervals by the method of electro-acoustic spraying. A complex highly concentrated effect of the ultrasonic method in a permanent process, based on the pulse energy, which leads to an increase in the plasticity of the material and is not associated with its heating. The law of electro-plastic deformation for a conducting material, taking into account the high density of the acting amperage in the process of active deformation at a constant rate, considered in this article, establishes a clear dependence of the strengthening of the substrate material. The process of concentration of electromagnetic and thermal fields in a conductive material with defects such as a crack makes it possible to use this technology to slow down the propagation of cracks while reducing the concentration of mechanical stresses.

Effects of static and dynamic femtosecond laser modifications of Ti/Zr multilayer thin films

The experimental study of the static and dynamic femtosecond laser ablation of the multilayer 15x(Ti/Zr)/Si system is reported. The layer-by-layer selective laser ablation mechanism was studied by analysis of the surface morphology and elemental composition in static single pulse irradiation in a range of pulse energy from 10 to 17 $$\upmu $$ μ J. The selective ablations, as number of concentric circles in modified spots are increased with the pulse energy. The boundary between the circles was shown a change in the depth, comparable to the thickness of the individual layers. Changes in the elemental composition at the edges are associated with the removal of the layer by layer. The dynamic multipulse irradiation was observed via the production of lines with laser-induced periodic surface structures (LIPSS) at different laser parameters (scan velocities and laser polarization). The spatial periodicity of the formed LIPSS depends on changes in the effective number of pulses and laser polarization, as well as the nature of the material. For better interpretation of the experimental results, simulations have been conducted to explore the thermal response of the multiple layered structure 15x(Ti/Zr) after static single pulse irradiation. Graphic Abstract

Characterization of micro hole on super alloy GH4037 and stainless steel 304 by millisecond-pulsed Nd:YAG laser processing

In this study, both super alloy GH4037 and stainless steel 304 were selected as experimental materials to be processed by LASERTEC 80 PowerDrill three-dimensional solid laser machining center. The structure of the micro hole was researched by 3D Laser Scanning Confocal Microscope and Scanning Electron Microscope (SEM). Meanwhile, The holes taper, entrance and exit ends diameter, microcrack, recast layer, orifice deposits and the heat affected zone (HAZ) were also investigated. The single factor experimental method was used to research the influences of defocusing amount, pulse energy, repetition frequency, and pulse duration on quality of micro holes. Experimental results indicated that the holes entrance and exit ends diameter enlarged with increased pulse energy from 3.4 J to 4.2 J. The entrance and exit ends diameter of holes decreased with increased pulse duration from 0.5 ms to 2.5 ms. Besides, the variation of holes diameter and taper were more obvious with repetition frequency changing from 10 Hz to 30 Hz, and variation range for the entrance and exit ends diameters and taper were not obvious with increased defocusing amount from −2 mm to 2 mm. The herein results indicated that pulse energy was one of the most significant influencing elements, and higher pulse energy could bring about lower hole taper within a certain range. Meanwhile, shorter pulse duration reduced splash and debris of holes surface. The recast layer, micro crack and HAZ were existed in the both kinds of experimental materials. Moreover, the microcrack and recast layer on holes wall of GH4037 were less than those of 304, and the HAZ in drilling hole for GH4037 was more than that of 304. The experimental results for the holes size were compared with corresponding simulation results under different defocusing amount respectively, which verified the accuracy of simulation results. Combining the above factors, the quality of micro holes drilling on super alloy GH4037 was better than stainless steel 304.