Search Results (628)

Sapphire (α-Al₂O₃) has been widely used in high-power lasers, optical windows, semiconductor substrates, radomes, and other applications due to its exceptional optical properties, high hardness, excellent chemical stability, and thermal resistance. However, machining sapphire poses significant challenges because of the material’s high hardness and brittleness. Traditional mechanical and chemical–mechanical machine methods often fail to meet the processing requirements for micro and nanoscale structures. Recently, the use of femtosecond lasers—with ultra-short pulses and extremely high peak power—has allowed for the precise machining of sapphire with minimal thermal damage, a method akin to cold processing. Femtosecond laser processing offers significant advantages in fabricating three-dimensional micro- and nanoscale structures, surface and internal modification, optical waveguide writing, grating fabrication and dissimilar materials welding. Thus, this paper systematically reviewed the research progress in femtosecond laser processing of sapphire, covering technical approaches such as ablation, hybrid processing and direct writing micro- and nanoscale fabrication. The capability of femtosecond laser processing to modulate sapphire’s optical properties, wettability and mechanical and chemical characteristics were discussed in detail. The current challenges related to efficiency, cost, process standardization and outlines future development directions, including high-power lasers, parallel processing, AI optimization and multifunctional integration were also analyzed. Full article

We demonstrate Kerr-lens mode-locked operation of a Tm,Ho:Ca(Gd,Y)AlO₄ laser pumped by a narrow-linewidth, continuous-wave Ti:sapphire laser at 797 nm. Soliton pulses as short as 145 fs are generated at 2087.8 nm in σ-polarization via soft-aperture Kerr-lens mode-locking, with an average output power of 203 mW (0.5% output coupler) at ~80.5 MHz. To the best of our knowledge, this result represents the first demonstration of a Kerr-lens mode-locked laser based on a Tm,Ho:Ca(Gd,Y)AlO₄ crystal exhibiting both structural and compositional disorder. Full article

Two-photon polymerization (2PP) is revolutionizing micro- and nanoscale manufacturing by enabling true 3D fabrication with feature sizes far below the diffraction limit—capabilities that traditional lithography cannot match. By using ultrafast femtosecond laser pulses and nonlinear absorption, 2PP initiates polymerization only at the laser’s focal point, offering unmatched spatial precision. This paper highlights key advancements driving the field forward: the development of new materials engineered for 2PP with improved sensitivity, mechanical strength, and the introduction of high-speed, parallelized fabrication strategies that significantly enhance throughput. These innovations are shifting 2PP from a prototyping tool to a viable method for scalable production. Applications now range from custom biomedical scaffolds to complex photonic and metamaterial structures, demonstrating their growing real-world impact. We also address persistent challenges—including slow writing speeds and limited material options—and explore future directions to overcome these barriers. With continued progress in materials and hardware, 2PP is well positioned to become a cornerstone of next-generation additive manufacturing. Full article

In the process of femtosecond pulsed laser machining of cemented carbide, the simulation study of multi-pulse laser ablation is of great significance in revealing the laser ablation effect and guiding the machining process. When performing modeling, the consideration of the two-temperature equation, cumulative effect, and the improvement in the energy attenuation term in the laser heat source have a great influence on the simulation accuracy, but there are few related studies. This study aims to solve the above three problems and establish a more accurate finite element simulation model to reveal the effect of femtosecond laser ablation of cemented carbide. In order to apply the dual-temperature equation, the thermophysical parameters are chosen to approximate similar materials through experiments; in order to consider the cumulative effect, the accumulation coefficients are obtained through experiments and corrected based on the energy accumulation model for the laser heat source. In order to consider the influence of multi-pulse laser processing on the energy decay term in the traditional laser body heat source, the energy decay term is expanded by transforming the starting surface of the attenuation. The multi-pulse laser two-temperature model is established based on the WC-6Co material, the temperature field distribution and ablation morphology of the sample surface under the action of femtosecond laser are obtained, and the accuracy of the simulation model is verified by experimental results. On this basis, the influence of the average power and the number of pulses of the multi-pulse laser on the ablation effect of the material is quantitatively investigated. Full article

The rapid advancement of high-performance electronics has intensified the demand for wide-bandgap semiconductor materials capable of operating under high-power and high-temperature conditions. Among these, silicon carbide (SiC) has emerged as a leading candidate due to its superior thermal conductivity, chemical stability, and mechanical strength. However, the high cost and complexity of SiC wafer fabrication, particularly in slicing and exfoliation, remain significant barriers to its widespread adoption. Conventional methods such as wire sawing suffer from considerable kerf loss, surface damage, and residual stress, reducing material yield and compromising wafer quality. Additionally, techniques like smart-cut ion implantation, though capable of enabling thin-layer transfer, are limited by long thermal annealing durations and implantation-induced defects. To overcome these limitations, ultrafast laser-based processing methods, including laser slicing and stealth dicing (SD), have gained prominence as non-contact, high-precision alternatives for SiC wafer exfoliation. This review presents the current state of the art and recent advances in laser-based precision SiC wafer exfoliation processes. Laser slicing involves focusing femtosecond or picosecond pulses at a controlled depth parallel to the beam path, creating internal damage layers that facilitate kerf-free wafer separation. In contrast, stealth dicing employs laser-induced damage tracks perpendicular to the laser propagation direction for chip separation. These techniques significantly reduce material waste and enable precise control over wafer thickness. The review also reports that recent studies have further elucidated the mechanisms of laser–SiC interaction, revealing that femtosecond pulses offer high machining accuracy due to localized energy deposition, while picosecond lasers provide greater processing efficiency through multipoint refocusing but at the cost of increased amorphous defect formation. The review identifies multiphoton ionization, internal phase explosion, and thermal diffusion key phenomena that play critical roles in microcrack formation and structural modification during precision SiC wafer laser processing. Typical ultrafast-laser operating ranges include pulse durations from 120–450 fs (and up to 10 ps), pulse energies spanning 5–50 µJ, focal depths of 100–350 µm below the surface, scan speeds ranging from 0.05–10 mm/s, and track pitches commonly between 5–20 µm. In addition, the review provides quantitative anchors including representative wafer thicknesses (250–350 µm), typical laser-induced crack or modified-layer depths (10–40 µm and extending up to 400–488 µm for deep subsurface focusing), and slicing efficiencies derived from multi-layer scanning. The review concludes that these advancements, combined with ongoing progress in ultrafast laser technology, represent research opportunities and challenges in transformative shifts in SiC wafer fabrication, offering pathways to high-throughput, low-damage, and cost-effective production. This review highlights the comparative advantages of laser-based methods, identifies the research gaps, and outlines the challenges and opportunities for future research in laser processing for semiconductor applications. Full article

In this paper, ultra-fast laser lift-off (LLO) of carbon nanotube (CNT)-integrated polyimide film (PI) was investigated by different laser burst mode and pulse intervals using the two-temperature model. By comparing the temperature field distributions of nanosecond, picosecond, and femtosecond lasers at different pulse intervals, it can be found that picosecond lasers cause a higher lattice temperature increase at the PI interface with specific pulse interval conditions. With the increase in the pulse interval, the lattice temperature of the three kinds of lasers decreased, indicating that the heat accumulation effect was weakened. In addition, under picosecond laser irradiation, the lattice temperature at the PI/glass interface of integrated CNTs could be significantly increased, which was significantly different from the system without integrated CNTs. The simulation results show that the picosecond laser is more suitable for LLO with an appropriate pulse interval, and the integration of CNTs at the PI/glass interface can effectively reduce the laser energy threshold required for the LLO process. Our work presents a new PI/CNT/glass model for ultra-fast laser low-threshold LLO and promotes the laser debonding technology in the fields of OLED and other optoelectronic chips. Full article

Ultrashort fiber lasers are one of the current research hotspots in the field of lasers. They have the advantages of compact structure and high beam quality. Passively mode-locking using saturable absorbers (SAs) is an important scheme for generating picosecond and femtosecond pulses. A deep understanding of the passive mode-locking mechanism is key to maturing ultrafast laser technology. In recent years, the passively mode-locking technology of SAs has been improved in material systems, device preparation, and cavity structures. SAs are primarily divided into artificial SAs and real SAs. Real SAs primarily include semiconductor saturable absorption mirrors (SEASAMs) and nanomaterials. Artificial SAs primarily include nonlinear optical loop mirrors (NOLMs), nonlinear multimode interference (NLMMI), nonlinear polarization rotation (NPR), and the Mamyshev oscillator. Herein, we mainly review passively mode-locked fiber lasers employing various SAs, as well as their working principles and technical characteristics. By focusing on the representative achievements, the developmental achievements of ultrafast lasers based on SAs are demonstrated. Finally, the prevailing challenges and promising future research directions in SA’s mode-locking technology are discussed. Full article

Raman lasers based on multimode graded-index (GRIN) fibers directly pumped by laser diodes are the object of intensive research, promising to produce high-power, high-quality beams at new wavelengths. In this paper, we demonstrate a pulsed operation of such a laser based on a 1 km 100/140 GRIN fiber in which a resonator is formed by a pair of FBGs: a high-reflective broadband input FBG and a tunable narrowband output FBG inscribed by fs laser pulses in the fundamental mode area of the core. In addition to beam quality improvement, the output FBG modulated by a piezoelectric nanopositioner with a frequency of 20–180 Hz generates laser pulses with a duration of 23–1.2 ms, respectively. The maximum power reached is 22 watts, and the signal spectrum widens significantly with increased pumping (>2 nm from the central wavelength of 976 nm). The pulse generation method used in this work introduces wavelength chirp in the individual pulse, which can be used in sensing and other applications. Full article

To meet the surface polishing requirements of aluminum nitride (AlN) ceramics, this study developed a multi-objective optimization experimental model based on response surface methodology (RSM), with surface roughness as the key optimization target. A systematic series of femtosecond laser polishing experiments were conducted. Polishing effectiveness and the evolution of material properties under different process parameters were comprehensively evaluated through surface morphology characterization, microhardness testing, friction and wear experiments, and energy-dispersive X-ray spectroscopy (EDS) analysis. The experimental results indicated that the optimal combination of process parameters, as determined by RSM optimization, was identified as a laser power of 17.43 W, pulse frequency of 292.29 kHz, and scanning speed of 1004.82 mm/s. Under these parameters, femtosecond laser polishing significantly reduced the surface roughness of the AlN ceramic, with the initial Ra value decreasing from 2.513 μm to 0.538 μm, a reduction of 78.57%. Compared to CO₂ laser polishing (R_a = 0.817 μm), femtosecond laser polishing demonstrated superior performance in enhancing surface quality. Analysis of the microstructural mechanisms revealed that the femtosecond laser, due to its ultra-short pulse characteristics, effectively suppressed the expansion of the heat-affected zone. It passivated surface microcracks through a photothermal ablation effect and reduced the thickness of the subsurface damage layer. Furthermore, the friction coefficient and wear rate of the polished samples decreased, indicating a significant improvement in wear resistance. On the numerical simulation front, a multi-physics model describing the interaction between the femtosecond laser and AlN ceramic was established based on the non-equilibrium two-temperature model (NTTM) coupled with solid mechanics. The key innovation of our model is the full coupling of heat transfer and solid mechanics, which allows for an accurate revelation of the material morphology evolution mechanism during femtosecond laser ablation. The model’s accuracy is confirmed by the excellent agreement with experimental results, showing relative errors of only 3.23% and 12.5% for the melt pool width and depth, respectively. Full article

Femtosecond laser has been widely utilized in functional microstructural surfaces for applications such as anti-reflection, radiative cooling, and self-cleaning. However, achieving high-efficiency manufacturing of high-consistency functional microstructures (with feature sizes ~1 μm) over large areas remains a challenge. Here, we report a femtosecond laser temporal and spatial modulation technique for fabricating large-area anti-reflective microholes on magnesium fluoride (MgF₂) windows. The beam was transformed into a Bessel beam to extend the Rayleigh length, enabling the fabrication of microhole arrays with sub-micron precision and surface roughness variations within 10 nm over a 6 μm focal position shift range (5–11 μm). By modulating MHz burst pulses, the aspect ratio of the microholes was increased from 0.3 to 0.7 without compromising a processing speed of 10,000 holes per second. As a proof of concept, large-area anti-reflective microholes were fabricated on a 20 mm × 20 mm surface of the MgF₂ window, forming a nanoscale refractive index gradient layer and achieving a transmittance increase to over 98%. This method provides a feasible solution for the efficient and high-consistency manufacturing of functional microstructures over large areas. Full article

Ytterbium-doped femtosecond fiber lasers are widely used in scientific research, industrial processing, and other fields due to their high quantum efficiency, wide gain bandwidth, and compact structure. This article addresses the problems of low processing efficiency and difficulty in increasing the average power of femtosecond lasers. A high repetition rate fiber chirped pulse amplification system is built, which uses a high repetition rate Figure-9 fiber laser as the seed source and an acousto-optic modulator (AOM) to shape the dense pulse train in the time domain. The main amplification stage uses a large mode field ytterbium-doped fiber to achieve full fiberization of the amplification system, and a volume grating (VBG) is selected as the pulse compressor to make the laser system highly integrated. When the repetition rate is 67.5 MHz, the compressed output laser has an average power of 20.5 W, a pulse width of 447 fs, a pulse train energy of 750 μJ, a spot ellipticity of 0.96, and a beam quality M² better than 1.4 ($M_x^2=1.33$, $M_y^2=1.16$). Full article

Intraocular lens (IOL) implantation is currently the most effective method for restoring vision following cataract surgery and is also used in cases of high myopia or hyperopia. However, IOL implantation eliminates accommodation, forcing patients to choose between corrected distance vision, requiring reading glasses for near tasks, or near vision supplemented by distance correction with spectacles. This limitation underscores the need for fully customized, patient-specific IOLs. To address this challenge, we performed femtosecond laser ablation experiments on polymethyl methacrylate (PMMA) IOLs using 200 fs pulses at 513 nm to investigate controlled surface modification. Laser-induced surface structuring offers a pathway to inscribe micron-scale patterns, including apodized features, in transparent polymers. To our knowledge, this is the first demonstration of femtosecond laser irradiation at 513 nm applied to IOL surfaces. Furthermore, this study is the first to combine scanning electron microscopy (SEM) and optical coherence tomography (OCT) as detection technologies to analyze and quantify ablation morphology and depth. The formation of smooth craters with minimal surrounding thermal damage highlights the potential of femtosecond laser processing as a promising tool for the development of customized, patient-tailored intraocular lenses. Full article

Laser-assisted hatching (LAH) is used during in vitro fertilization (IVF) to improve the chances of embryo implantation into the uterine wall by creating a small, precise opening in its outer shell (zona pellucida). The primary objective of this study was to evaluate the safety profile of LAH performed using an infrared femtosecond laser system (λ = 1028 nm, E = 155 nJ, and I = 6.5 TW/cm²). We aimed to identify and quantify the potential biological effects of the laser and compare them with results from previous studies that used visible wavelength laser pulses (λ = 514 nm, E = 49 nJ, and I = 2.5 TW/cm²). To achieve this, we designed a controlled experiment using a mouse model. A critical component of our safety assessment involved quantifying the levels of reactive oxygen species (ROS) and analyzing the expression of heat-shock proteins (HSPs). Robust analyses revealed no statistically significant differences in either ROS production or HSP expression—assessed at both the protein and mRNA levels—between embryos in the negative control group and those subjected to the femtosecond LAH procedure. This key finding indicates that neither infrared nor visible femtosecond laser microsurgery of the zona pellucida induced a detectable oxidative or thermal stress response within the tested parameters. Full article

Carbon-fiber-reinforced plastic (CFRP) machining by ultrashort-pulse lasers promises high precision but is limited due to the heterogeneous epoxy–carbon fiber structure, which creates heat-affected zones and variable kerf quality. This work investigates synthesized copper hydroxyphosphate as a laser-absorbing additive to improve femtosecond (1030 nm) laser ablation of CFRP. Copper hydroxyphosphate particles were synthesized hydrothermally and incorporated into an epoxy matrix to produce single-ply CFRP laminates. Square patterns (0.5 × 0.5 mm) were ablated with a pulse energy of 0.5–16 μJ. Then, ablated volumes were profiled and materials characterized by SEM and EDS. In neat epoxy the copper additive reduced optimum ablation efficiency and decreased penetration depth, while producing smoother, less porous surfaces. In contrast, CFRP with copper hydroxyphosphate showed increased efficiency and higher penetration depth. SEM and EDS analyses indicate more uniform matrix removal and retention of resin residues on fibers. These results suggest that copper hydroxyphosphate acts as a local energy absorber that trades volumetric removal for improved surface quality in epoxy and enhances uniformity and process stability in CFRP femtosecond laser machining. Full article

A glow discharge polymer (GDP) has unique physical properties—transparency, brittleness, and hardness—that pose challenges for traditional mechanical machining techniques. We have investigated the microhole fabrication of GDP films using shaped femtosecond laser pulses to study the influence of pulse shape, delay between subpulses, and focusing position on processing precision and efficiency. By precisely controlling pulse characteristics, such as duration, energy, and subpulse intervals, the efficiency, hole morphology, and processing quality were significantly improved. The experimental results demonstrated that femtosecond lasers with subpulses produce smaller and more uniform microholes compared to transform-limited pulses. Furthermore, both the pulse shape and focusing position of the laser were found to further influence ablation efficiency. This study establishes, for the first time, the critical role of temporal pulse shaping in optimizing the femtosecond laser drilling of GDP films, which provides valuable information on optimizing femtosecond laser parameters for precision processing of polymer films and advances the potential for microhole fabrication in industrial applications. Full article