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A comprehensive approach for characterisation of the deposited energy density during laser-matter interaction in liquids and solids
摘要： We present a novel approach for characterisation of ultrafast laser-matter interaction processes both in solids and liquids under extreme conditions of microplasma generation. By combination of three-dimensional propagation imaging, absorption measurements, shadowgraphy and photoacoustic imaging we can restore plasma electron density distribution, laser pulse fluence profile and the value of deposited energy density inside the bulk of the material and characterise the regime of the laser pulse propagation. The developped concept is important to understand the physics of ultrafast laser-matter interaction with strong implications for precision control of laser micromachining, bioprocessing and biotreatment.
关键词： three-dimensional propagation imaging,photoacoustics,femtosecond filamentation,laser-matter interaction,deposited energy density,shadowgraphy
更新于2025-09-23 15:21:01
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Control of Multiple Filamentation of Femtosecond Laser Pulses in Air
摘要： The results are presented of experiments on controlling the characteristics of the multiple filamentation domain of femtosecond laser pulses along atmospheric paths via variations in the initial spatial focusing, beam radius, and pulse energy, as well as the optical field structure at the initial beam aperture.
关键词： filamentation,femtosecond pulse,bimorph deformable mirror,laser radiation,postfilamentation light channel,self-focusing
更新于2025-09-23 15:21:01
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[IEEE 2019 6th International Conference on Instrumentation, Control, and Automation (ICA) - Bandung, Indonesia (2019.7.31-2019.8.2)] 2019 6th International Conference on Instrumentation, Control, and Automation (ICA) - A Portable Surface Roughness Measurement System Using Laser Speckle Imaging Based on GLCM
摘要： This paper summarizes the generation of sub-single-cycle infrared (IR) pulses through a laser filament and the detailed properties of the generated pulses. The fundamental (ω1) and second harmonic (ω2) of 30-fs Ti:sapphire amplifier output were focused into nitrogen gas and produced phase-stable broadband IR pulses (ω0) by four-wave difference frequency generation (ω1 + ω1 ? ω2 → ω0) through filamentation. The spectrum spread from 200 to 5500 cm?1, corresponding to ～3.5 octaves. The waveform of the sub-single-cycle pulse was completely characterized with the frequency-resolved optical gating capable of a carrier-envelope phase determination. The pulse duration was measured as 6.9 fs, which was 0.63 times the period of the carrier frequency, 3000 cm?1. The carrier-envelope phase of the IR pulse was passively stabilized, and the instability of the phase was estimated as 154-mrad rms over 2.5 h. We also summarize a particular behavior of the spectral phase of the sub-single-cycle pulse; the phase of high-frequency components of the generated pulses changes continuously and linearly with the relative phase between the two-color input pulses, whereas the phase of the low-frequency components takes only two discrete values. The phase behavior is a unique feature of single-cycle pulses generated with a passive carrier-envelope phase stabilization scheme.
关键词： single-cycle pulse,infrared,ultrashort pulse,four-wave difference frequency generation,Filamentation
更新于2025-09-23 15:19:57
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Direct electron acceleration with a linearly polarized laser beam in a two-dimensional magnetized plasma channel
摘要： We examine the electron acceleration induced by an ultra-relativistic intensity laser–plasma interaction in a two-dimensional plasma channel in the presence of a self-generated transverse magnetic field. We find that the electron dynamics is strongly affected by the laser pulse polarization angle, plasma density, and magnetic field strength. We investigate in detail, the dependencies of the electron acceleration in terms of different parameters and find excellent agreement with non-magnetized plasma in the absence of the magnetic field. The numerical results show that the self-generated magnetic field plays a constructive role in the electron acceleration process. It is shown that electron acceleration is more affected by self-generated magnetic field for the laser radiations with large polarization angles. The numerical results show the maximum enhancement for electron acceleration for a laser radiation with polarization angle θ = π/2.
关键词： filamentation instability,two-fluid model,Electron beams,magnetized plasma
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Systematically Varying the Active Material Volume in a Photonic Crystal Nanolaser
摘要： This paper summarizes the generation of sub-single-cycle infrared (IR) pulses through a laser filament and the detailed properties of the generated pulses. The fundamental (ω1) and second harmonic (ω2) of 30-fs Ti:sapphire amplifier output were focused into nitrogen gas and produced phase-stable broadband IR pulses (ω0) by four-wave difference frequency generation (ω1 + ω1 ? ω2 → ω0) through filamentation. The spectrum spread from 200 to 5500 cm?1, corresponding to ～3.5 octaves. The waveform of the sub-single-cycle pulse was completely characterized with the frequency-resolved optical gating capable of a carrier-envelope phase determination. The pulse duration was measured as 6.9 fs, which was 0.63 times the period of the carrier frequency, 3000 cm?1. The carrier-envelope phase of the IR pulse was passively stabilized, and the instability of the phase was estimated as 154-mrad rms over 2.5 h. We also summarize a particular behavior of the spectral phase of the sub-single-cycle pulse; the phase of high-frequency components of the generated pulses changes continuously and linearly with the relative phase between the two-color input pulses, whereas the phase of the low-frequency components takes only two discrete values. The phase behavior is a unique feature of single-cycle pulses generated with a passive carrier-envelope phase stabilization scheme.
关键词： single-cycle pulse,infrared,ultrashort pulse,four-wave difference frequency generation,Filamentation
更新于2025-09-19 17:13:59
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Engineering black titanium dioxide by femtosecond laser filament
摘要： We propose an approach, by utilizing the propagation of femtosecond laser pulses in the filamentation region in air, to achieve black titanium dioxide (TiO2), a promising material for efficient photocatalysis. It is found that the black TiO2 engineered by femtosecond laser filament in both solution and air environments shows significantly improved absorption in a broad spectral range from 400 to 2500 nm. In addition, the engineered black TiO2 shows a certain degree of enhanced absorption in the microwave range. The structural and elemental analysis of the processed TiO2 suggest that the absorption enhancement is mainly ascribed to the filament-induced disorder and dopant impurity in the surface layer of crystalline TiO2. Our technique provides an alternative way to engineer black TiO2 with the capability of absorbing the solar energy across a broad spectrum that can be useful for various applications in optoelectronics and photochemistry.
关键词： femtosecond laser filamentation,disordered surface,solar energy,titanium dioxide,absorption enhancement,laser processing
更新于2025-09-19 17:13:59
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Modification characteristics of filamentary traces induced by loosely focused picosecond laser in sapphire
摘要： The ability of loosely focused picosecond laser to induce filamentation (4.8 times the Rayleigh length) in sapphire was confirmed. The morphology and microstructure of the filamentary traces under typical pulse energy were studied, in which the colorful birefringence phenomenon and damage defects were detected in sapphire. Irreversible ceramic-like polycrystalline microstructures were formed in filamentary traces, and the phase transition from α-Al2O3 to γ-Al2O3 directly reflected the thermal effect of picosecond laser filamentation. According to the filamentary characteristics, a continuous filamentary channel with a uniform diameter of 33 μm and a length of 7443 μm was obtained by gradually raising the focal position. The research provides first-hand information for the high throughput micro-cutting, micro drilling and thin slicing of sapphire based on ultrafast laser non-linear effects.
关键词： Phase transition,Modification,Picosecond laser,Filamentation,Sapphire
更新于2025-09-19 17:13:59
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Lasers Improve Display Glass Cutting
摘要： Non-contact glass cutting by laser offers an attractive alternative to mechanical methods in display fabrication. There are several laser technologies and processing techniques in actual use, each with its own characteristics and advantages.
关键词： CO2 lasers,laser glass cutting,non-contact cutting,filamentation cutting,display fabrication,laser ablation,CO lasers
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Miramar Beach, FL, USA (2019.8.19-2019.8.21)] 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Single Shot Axially Resolved Femtosecond Laser Filament Profiles
摘要： An array of synchronized microphones measures energy deposition along the length of laser filament in a single shot. A spread of collapse location positions due to air turbulence and laser energy fluctuations causes a pronounced difference between single shot measurements and conventional multi-shot averaging.
关键词： turbulence,filamentation
更新于2025-09-16 10:30:52
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Simulation of Self-focusing of Femtosecond Laser Pulses with Normal Dispersion in Air Using the Diffraction-Beam Tube Approach
摘要： Based on numerical simulation and qualitative analysis, the effect of the group velocity dispersion on the formation of light structures during self-focusing and filamentation of femtosecond Ti:sapphire laser pulses in air is studied. The main features of the filamentation have been determined at various pulse duration, initial beam radii, and peak radiation powers based on the results of numerical solutions of the nonlinear Schr?dinger equation in a Kerr-plasma dissipative dispersion medium and using the diffraction-beam tube approach. Dispersion is detected in the cases where the dispersion length is not a minimum at the scale of the process. It is shown that the relative (normalized to Rayleigh length) coordinate of the beginning of filamentation increases as the dispersion distortions of the pulse increase, and the filamentation channel length is reduced. For shorter laser pulses (tens of femtoseconds), the filamentation ceases as the laser beam radius increases. The size of the energy-replenishing diffraction-beam tube and the angular divergence of postfilamentation light channels increase for this class of pulses.
关键词： filamentation,self-focusing,femtosecond laser pulses,diffraction-beam tube,normal dispersion
更新于2025-09-12 10:27:22