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- 摘要
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High order harmonic generation in solids: a review on recent numerical methods
摘要： Interaction of intense lasers with solid materials offers an alternative way to achieve high-order harmonic generation (HHG). Since the underlying mechanisms of the harmonic emission remain uncertain, a large number of theoretical studies have been proposed to explain the experimental findings in this fast-growing field. Here, we review the primary numerical methods and present a brief perspective of HHG in solids.
关键词： Ultrafast laser,strong field,numerical simulations,laser-crystal interaction,solid materials,high-order harmonic generation
更新于2025-09-23 15:23:52
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Micro/nano processing of natural silk fibers with near-field enhanced ultrafast laser; ?????¨è????o?￠???oè????????????ˉ1?¤????è?????è??è??????o3????·￥;
摘要： Silkworm silk fiber is an attractive material owing to its remarkable mechanical characteristics, excellent optical properties, and good biocompatibility and biodegradability. However, nano-processing of the silk fiber is still a challenge limiting its applications in nanoengineering and related fields. Herein, we report localized near-field enhancement-assisted ablation with an ultrafast laser to break this bottleneck. Localized processing of silk fiber, including nano-holing, nano-grooving, and cutting could retain the key molecular structure building blocks and the pristine functionality of the silk fiber. An extremely narrow nanohole with a width of ~64 nm was successfully achieved. The processed silk fiber can be used to transfer micro/nanoparticles and drugs, showing potential for biomedical engineering. The processing strategy developed in this study can also be extended to other materials, paving a new way for fabricating functional nanostructures with precisely controlled size and morphology.
关键词： nano-processing,ultrafast laser,drug delivery,silk fiber,laser ablation
更新于2025-09-23 15:21:01
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Environmentally Stable 1.56-??m Femtosecond Laser System With Discontinuous Selectable Repetition Rate
摘要： We demonstrate here an environmentally stable and compact Er-doped fiber laser system capable of delivering sub-100-fs pulse duration with discontinuous selectable repetition rate from 10 to 70 MHz. This laser source employs a SESAM harmonic mode-locked soliton laser to facilitate tunable repetition rate. A single-mode-fiber (SMF) amplifier and a double-cladding-fiber (DCF) amplifier (both with double-pass configuration) bridged by a three-stage YVO4-based divider are used to manage the dispersion map and boost the seed pulses. With the help of ×8 replicas, the seed pulses are simultaneously amplified and compressed with 90% recombining efficiency, generating 4.60-nJ pulse energy at 10 MHz and 6.13-nJ pulse energy at 70 MHz. The main advantage of the proposed laser system is that when pulse repetition rate is switched on-demand, the pulse duration can be kept almost unchanged only by simply adjusting the pump powers of the fiber amplifiers, instead of changing any optical device (the spacing between gratings or the length of fibers).
关键词： fiber amplifiers,Mode-locked Laser,ultrafast laser,tunable repetition rate
更新于2025-09-23 15:21:01
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Deep and high precision cutting of alumina ceramics by picosecond laser
摘要： Ceramics possess high thermal and chemical resistance, low density, and high compressive strength; however, the machining complications imposed by their inherent brittleness limit their range of applications. Laser cutting technology can offer an automated manufacturing technique for machining these brittle materials. In this paper, a laser cutting method, so-called wobbling, was developed for performing deep, high precision, and defect-free laser cutting of industrial grade alumina ceramics. This work explored picosecond laser process parameters such as focal position, linear speed, and wobble amplitude in order to control cut depth and optimize cut quality in terms of kerf width, kerf taper, surface cleanness, while avoiding crack formation. The morphology and cut quality were evaluated using 3D laser scanning microscopy and scanning electron microscopy (SEM). Picosecond laser cutting process parameters were optimized, achieving a maximum material removal rate of ~10 mm3/min. It was shown that the laser cutting process developed via these experiments represents an effective and efficient manufacturing tool that can be incorporated in engineered net shaping systems.
关键词： Laser cutting,Material removal rate,Ablation,Ultrafast laser micromachining,Alumina ceramics
更新于2025-09-23 15:21:01
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Wetting and spreading behaviors of Al-Si alloy on surface textured stainless steel by ultrafast laser
摘要： An ultrafast laser was used to ablate the surface of stainless steel. Periodical surface micro-textures including micro-grooves, micro-pits and micro/nano-ripples were successfully fabricated. As a typical reactive wetting system, Al-Si alloy was used to study the wetting and spreading behaviors on the laser patterned surfaces of stainless steel. The results showed that initial, rapid spreading and gradient balance stages were found in the spreading process. By comparing to the primitive surface, Al-Si alloy exhibited worse wettability on the surface with micro-grooves and micro-pits because of the geometrical characteristics and nano-scale oxides residuals after laser processing; however, Al-Si alloy showed better wettability on the surface with micro/nano-ripples owing to the formation of micro/nano hierarchically patterns and the resultant improved capillary actions. The interfacial reaction layer formed during wetting and spreading processes were also investigated. The surface micro-textures were found to enhance the interfacial metallurgical reactions, thus increasing the thickness of the reaction layer. This work provides a new method to improve the wettability, spreadability and metallurgical reactions of Al-Si/stainless steel reactive wetting system and may extend its use in other reactive wetting systems. This method may be able to improve brazing, soldering, coating and other processes involving solid/liquid interfacial interactions.
关键词： Reactive wetting system,Wetting and spreading,Intermetallic compounds,Ultrafast laser processing,Surface micro-textures
更新于2025-09-23 15:21:01
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Laser machined ultralow water adhesion surface by low pressure processing
摘要： Ultralow water adhesion aluminum surface has been fabricated by eco friendly low pressure processing technique. The laser patterned surface shows interconnected spongy porous nanostructures with micro packets at regular intervals. The micro volume of air present inside the interconnected porous surface structure together with the adsorbed hydrocarbons by low pressure processing leads to ultralow water adhesion surface. Application of bigger droplet volumes to the patterned surface showed a decrease in static contact angle measurement due to larger radius of curvature and axisymmetrical compared to the smaller droplets.
关键词： Sliding angle,Ultrafast laser,Low pressure,Wetting,Adhesion
更新于2025-09-23 15:21:01
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41.8??W output power, 200??kHz repetition rate ultra-fast laser based on Yb:YAG single crystal fiber(SCF)amplifier
摘要： We demonstrate a high repetition rate, high energy chirped pulse amplification (CPA) system based on single crystal fiber (SCF) amplifier. With home-made all-fiber laser as the seed laser and Yb:YAG rod, SCF as the amplification gain medium, an output power of 61.8 W at 200 kHz repetition rate has been obtained. To the best of our knowledge, this is the highest power based on SCF at hundreds of kHz repetition rate. The measured M2 values are approximately 1.241 in the horizontal and 1.186 in the vertical direction. The spectrum width is 3.8 nm, which support Fourier transform-limited pulse duration of 411 fs. An average power of 41.8 W with pulse duration of 1.5 ps has been obtained after the chirped volume Bragg grating (CVBG) compressor, which will be compressed to hundreds of fs with accurate chirp compensation.
关键词： Ultrafast laser,SCF,Fiber laser,CPA
更新于2025-09-23 15:19:57
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Crack behavior in ultrafast laser drilling of thermal barrier coated nickel superalloy
摘要： Quantitative analysis is required to explore the mechanism of crack generation in ultrafast laser drilling of thermal barrier coated nickel superalloy. In this study, a simple thermo-mechanical coupled model is established to obtain temperature history, phase transformation stress and thermal stress during drilling process, in which laser beam scanning, laser intensity attenuation, the nonlinear relationship between drilling depth and drilling time are involved. The induced stress obtained from the present model is compared with the results by digital image correlation (DIC) method. According to the crack distribution around the drilled hole, the present model is used to explain the mechanism of crack behavior in drilling of multilayer materials. Finally, the strategy using low pulse repetition rate or water jet assisted method is suggested to reduce the thermal effect in ultrafast laser drilling process.
关键词： TBC,Phase transformation stress,Thermal stress,Crack behavior,Ultrafast laser,Laser drilling
更新于2025-09-23 15:19:57
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Expansion dynamics and chemistry evolution in ultrafast laser filament produced plasmas
摘要： Laser ablation in conjunction with optical emission spectroscopy is a potential non-contact, standoff detection method for all elements in the periodic table and certain isotopes such as radionuclides. Currently, significant development efforts are on-going to use ultrafast laser filaments for remote detection of materials. The application of filaments is of particular interest in extending the range of stand-off capability associated with elemental and isotopic detection via laser-induced breakdown spectroscopy. In this study, we characterize the expansion dynamics and chemical evolution of filament-produced uranium (U) plasmas. Laser filaments are generated in the laboratory by loosely focusing 35 femtosecond (fs), 6 milli Joule (mJ) pulses in air. Two-dimensional spectrally-integrated and time-resolved imaging was performed to study hydrodynamics and evolution of U atomic and UO molecular emission in filament-produced U plasmas. Our results highlight that filament ablation of U plasmas gives a cylindrical plasma plume morphology with an appearance of plume splitting into slow and fast moving components at later times of its evolution. Emission from the slow-moving region shows no distinct spectral features (i.e. broadband-like) and is contributed in part by nanoparticles generated during ultrafast laser ablation. Additionally, we find U atoms and U oxide molecules (i.e. UO, UxOy) co-exist in the filament produced plasma, which can be attributed to the generation of low-temperature plasma conditions during filament ablation.
关键词： optical emission spectroscopy,Laser ablation,plasma chemistry,ultrafast laser filaments,uranium plasmas
更新于2025-09-23 15:19:57
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A Miniature Fibre-Optic Raman Probe Fabricated by Ultrafast Laser-Assisted Etching
摘要： Optical biopsy describes a range of medical procedures in which light is used to investigate disease in the body, often in hard-to-reach regions via optical fibres. Optical biopsies can reveal a multitude of diagnostic information to aid therapeutic diagnosis and treatment with higher specificity and shorter delay than traditional surgical techniques. One specific type of optical biopsy relies on Raman spectroscopy to differentiate tissue types at the molecular level and has been used successfully to stage cancer. However, complex micro-optical systems are usually needed at the distal end to optimise the signal-to-noise properties of the Raman signal collected. Manufacturing these devices, particularly in a way suitable for large scale adoption, remains a critical challenge. In this paper, we describe a novel fibre-fed micro-optic system designed for efficient signal delivery and collection during a Raman spectroscopy-based optical biopsy. Crucially, we fabricate the device using a direct-laser-writing technique known as ultrafast laser-assisted etching which is scalable and allows components to be aligned passively. The Raman probe has a sub-millimetre diameter and offers confocal signal collection with 71.3% ± 1.5% collection efficiency over a 0.8 numerical aperture. Proof of concept spectral measurements were performed on mouse intestinal tissue and compared with results obtained using a commercial Raman microscope.
关键词： Raman spectroscopy,ultrafast laser-assisted etching,micro-optics,optical biopsy
更新于2025-09-23 15:19:57