Search Results (398)

In this paper, we develop a peridynamic computational framework to analyze thermomechanical interactions in fractured thin films subjected to ultrashort-pulsed laser excitation, employing nonlocal discrete material point discretization to eliminate mesh dependency artifacts. The generalized Cattaneo–Fourier thermal flux formulation uncovers contrasting dynamic responses: hyperbolic heat propagation ($F_T=0$) generates intensified temperature localization and elevates transient crack-tip stress concentrations relative to classical Fourier diffusion ($F_T=1$). A GSSSS (Generalized Single Step Single Solve) i-Integration temporal scheme achieves oscillation-free numerical solutions across picosecond-level laser–matter interactions, effectively resolving steep thermal fronts through adaptive stabilization. These findings underscore hyperbolic conduction’s essential influence on stress-mediated fracture evolution during ultrafast laser processing, providing critical guidelines for thermal management in micro-/nano-electromechanical systems. Full article

Phase noise constitutes a pivotal performance parameter in microwave systems, and the evolution of microwave signal sources presents new demands on phase noise analyzers (PNAs) regarding sensitivity and bandwidth. Traditional electronics-based PNAs encounter significant limitations in meeting these advanced requirements. This paper provides an overview of recent progress in photonics-based microwave PNA research. Microwave photonic (MWP) PNAs are categorized into two main types: phase-detection-based and frequency-discrimination-based architectures. MWP phase-detection-based PNAs utilize ultra-short-pulse lasers or optical–electrical oscillators as reference sources to achieve superior sensitivity. On the other hand, MWP frequency-discrimination-based PNAs are further subdivided into photonic-substitution-type PNA and MWP quadrature-frequency-discrimination-based PNA. These systems leverage innovative MWP technologies to enhance overall performance, offering broader bandwidth and higher sensitivity compared to conventional approaches. Finally, the paper addresses the current challenges faced in phase noise measurement technologies and suggests potential future research directions aimed at improving measurement capabilities. Full article

Optically pumped semiconductor disk lasers—known as vertical-external-cavity surface-emitting lasers (VECSELs)—are promising devices for ultrashort pulse formation. For it, a “SESAM-free” approach labeled “self-mode-locking” received considerable attention in the past decade, relying solely on a chip-related nonlinear optical property which can establish adequate pulsing conditions—thereby suggesting a reduced reliance on a semiconductor saturable-absorber mirror (the SESAM) in the cavity. Self-mode-locked (SML) VECSELs with sub-ps pulse durations were reported repeatedly. This motivated investigations on a Kerr-lensing type effect acting as an artificial saturable absorber. So-called Z-scan and ultrafast beam-deflection experiments were conducted to emphasize the role of nonlinear lensing in the chip for pulse formation. Recently, in addition to allowing stable ultrashort pulsed operation, self-starting mode-locked operation gave rise to another emission regime related to frequency comb formation. While amplitude-modulated combs relate to signal peaks in time, providing a so-called pulse train, a frequency-modulated comb is understood to cause quasi continuous-wave output with its sweep of instantaneous frequency over the range of phase-locked modes. With gain-bandwidth-enhanced chips, as well as with an improved understanding of the impacts of dispersion and nonlinear lensing properties and cavity configurations on the device output, an enhanced employment of SML VECSELs is to be expected. Full article

Although thick electrodes hold significant potential for enhancing battery energy density, their practical application is limited by restricted ion transport kinetics. Constructing porous structures within thick electrodes is a widely adopted strategy to address this limitation, but it often compromises mass retention and mechanical integrity. In this study, a microchannel structure that balances the electrochemical and mechanical properties of the electrode was identified through simulation and precisely fabricated using femtosecond laser technology. Furthermore, the ultra-short pulse duration and high pulse energy of femtosecond lasers introduce oxygen vacancies into the electrode material, thereby enhancing its electrical conductivity. The obtained electrode exhibited excellent electrochemical performance under high-rate charging and discharging conditions, achieving significantly enhanced cycling stability and capacity retention, with a capacity 1.99 times greater than that of the unstructured electrode after 100 cycles. Meanwhile, the mechanical stability of the laser-processed electrode was maintained. This study provides new insights into the structural design and processing of the thick electrode and contributes to advancements in the field of energy storage. Full article

Glass-based microfluidic devices are essential for applications such as diagnostics and drug discovery, which utilize their optical clarity and chemical stability. This review systematically analyzes pulsed laser micromachining as a transformative technique for fabricating glass-based microfluidic devices, addressing the limitations of conventional methods. By examining three pulse regimes—long (≥nanosecond), short (picosecond), and ultrashort (femtosecond)—this study evaluates how laser parameters (fluence, scanning speed, pulse duration, repetition rate, wavelength) and glass properties influence ablation efficiency and quality. A higher fluence improves the material ablation efficiency across all the regimes but poses risks of thermal damage or plasma shielding in ultrashort pulses. Optimizing the scanning speed balances the depth and the surface quality, with slower speeds enhancing the channel depth but requiring heat accumulation mitigation. Shorter pulses (femtosecond regime) achieve greater precision (feature resolution) and minimal heat-affected zones through nonlinear absorption, while long pulses enable rapid deep-channel fabrication but with increased thermal stress. Elevating the repetition rate improves the material ablation rates but reduces the surface quality. The influence of wavelength on efficiency and quality varies across the three pulse regimes. Material selection is critical to outcomes and potential applications: fused silica demonstrates a superior surface quality due to low thermal expansion, while soda–lime glass provides cost-effective prototyping. The review emphasizes the advantages of laser micromachining and the benefits of a wide range of applications. Future directions should focus on optimizing the process parameters to improve the efficiency and quality of the produced devices at a lower cost to expand their uses in biomedical, environmental, and quantum applications. Full article

Direct-writing submicron copper circuits on glass with laser precision—without lithography, vacuum deposition, or etching—represents a transformative step in next-generation microfabrication. We present a high-resolution, maskless method for metallizing glass using ultrashort pulse Bessel beam laser processing, followed by silver ion activation and electroless copper plating. The laser-modified glass surface hosts nanoscale chemical defects that promote the in situ reduction of Ag⁺ to metallic Ag⁰ upon exposure to AgNO₃ solution. These silver seeds act as robust catalytic and adhesion sites for subsequent copper growth. Using this approach, we demonstrate circuit traces as narrow as 0.7 µm, featuring excellent uniformity and adhesion. Compared to conventional redistribution-layer (RDL) and under-bump-metallization (UBM) techniques, this process eliminates multiple lithographic and vacuum-based steps, significantly reducing process complexity and production time. The method is scalable and adaptable for applications in transparent electronics, fan-out packaging, and high-density interconnects. Full article

High-repetition-rate targets present an opportunity for developing diagnostic tools for on-demand calibration at high-power laser facilities for consistent performance and reproducibility during experimental campaigns. The non-linear change in transmission associated with a laser-driven plasma mirror, based on high-repetition rate targets, has been used in a Frequency Resolved Optical Gating (FROG) configuration to analyze the spectral phase for near-infrared pulses far from the Fourier limit. Three types of targets were compared for characterizing pulses in the 1–8 ps range: a glass slide, a polymer tape, and a thin liquid sheet created by two impinging micrometer-scale jets. The thin liquid film had the best mechanical stability and introduced the least spectral distortion, allowing the most robust reconstruction of the temporal intensity profile. The spectral phase was reconstructed using a non-iterative algorithm, which reproduced the second-order phase distortions induced with an acousto-optic programmable dispersive filter with an RMS error of 6.2%, leading to measured pulse durations with an RMS deviation ranging from 1% for pulses of 6.8–7.8 ps up to 7.5% for pulses around 1 ps. Full article

In this study, we have demonstrated an ultrafast Tm-doped fiber laser utilizing the nonlinear multimode interference (NL-MMI) effect, with a single mode fiber–grade index multimode fiber–single mode fiber (SMF-GIMF-SMF) structure serving as the saturable absorber (SA). In addition to stable pulses, mode-locked pulses with chaotic features can be obtained in this fiber laser, characterized by a high average output power and pulse energy, resembling noise-like pulses. By employing the time-stretch dispersive Fourier transform (TS-DFT) technology, it can be seen that the sub-pulses constituting these pulses exhibit noisy characteristics with random intensities and energies. Furthermore, the numerical simulations elucidate the corresponding generation mechanism and dynamic evolution. These findings significantly enhance the comprehension of pulse dynamics and offer novel insights into the technological development and application prospects of ultrafast fiber lasers. Full article

Within the framework of classical dynamics, the impact of laser amplitude on the cross-collision between a linearly polarized intense laser pulse and a relativistic electron under tight focusing conditions was investigated via numerical simulation. As the laser amplitude intensifies, the z-axis oscillation trajectory of the electron elongates. The spatial radiation angular distribution of the electron transforms from a “hill shape” to a “comet shape”, and the radiation peak shifts toward the direction of smaller polar angle, with the radiation concentrating in the forward position. The time spectrum is symmetrical; the number of peaks is reduced from multiple peaks to three peaks; and the relative height of the main peak and secondary peaks increases, with the time distribution gradually concentrating, which can be regarded as an ultrashort attosecond single pulse. The spectrum exhibits a multi-peak distribution trend. When the laser amplitude is relatively strong, radiation with a more concentrated frequency range and better quality can be output. The above research findings are beneficial for generating X-rays of higher quality and can be applied in fields such as biomedicine and atomic physics. Full article

We report an ultra-short-pulse laser welding process that allows one to consistently weld Borofloat^® 33 glass to aluminum with a shear strength above 50 MPa. We explored the morphology of the welding seam and quantified the quality of the bonding by statistically determining the shear strength with more than 30 samples. The results of the shear strength tests indicate that the intrinsic shear strength of the aluminum serves as the upper limit of the glass-to-metal bond. Full article

Picosecond lasers are gaining increasing popularity in dermatology and aesthetic medicine due to their favorable safety profile and a wide range of therapeutic applications. While originally employed primarily for tattoo removal, their versatility has extended their use to the treatment of various aesthetic skin conditions, including hyperpigmentation, acne scars, stretch marks, and signs of photoaging. Owing to their ultra-short pulse duration, picosecond lasers effectively target pigment particles and stimulate dermal remodeling, offering patients a safe and effective solution to improve the appearance of their skin. The introduction of the picosecond laser into clinical dermatology practice marks a notable advancement in addressing a broad spectrum of skin problems. Full article

A polarization-maintaining all-fiber laser source based on a nonlinear amplifying loop mirror with broadband operation (64 nm) around 1920 nm is demonstrated. The oscillator can generate 66 pJ up-chirped dissipative soliton pulses at a repetition rate of 22.8 MHz with a high polarization extinction ratio of 17 dB. By adding a polarization controller to the polarization-maintaining dispersion-compensating fiber, the filter behavior can be adjusted allowing for the tuning of the emission to a center wavelength of 1878 nm, 1907 nm, and 1926 nm. Using an all-polarization-maintaining single-mode fiber amplifier with anomalous dispersion, the pulses are amplified to 0.9 nJ and compressed to a near Fourier-limited pulse duration of 170 fs with a peak power of 4.3 kW. Such all-fiber-based sources are attractive due to their compact size, high beam quality, and good environment stability. Full article

Overcoming the limitations of powder-based additive manufacturing processes is a crucial aspect for the manufacturing of patient-specific sophisticated implants with tailored properties. Within this work, a novel manufacturing process for the fabrication of polymer-based implants is proposed. This manufacturing process is inspired by the laminated object manufacturing technology and is based on using thin films as raw material, which are processed using an ultrafast laser source. Utilizing thin films as a starting material helps to avoid powder contamination during additive manufacturing, thus supporting the generation of internal cavities that can be filled with secondary phases. Additionally, the use of medical materials mitigates the burden of a later certification of potential implants. Furthermore, the ultrafast laser supports the generation of highly resolved structures smaller than the average layer thickness (from 50 to 100 µm) through material ablation. These structures can be helpful to obtain progressive part properties or a targeted stress flow, as well as a specified release of secondary phases (e.g., hydrogels) upon load. Within this work, first investigations on the joining, cutting, and structuring of thin polymer films with layer thickness of between 50 and 100 µm using a ps-pulsed laser are reported. It is shown that thin film sizes of around 50 µm could be structured, joined, and cut successfully using ultrafast lasers emitting in the NIR spectral range. Full article

Electron–ion radiative recombination in the presence of a bicircular laser pulse is analyzed beyond the dipole approximation. A bicircular pulse consists of two counter-rotating circularly polarized laser pulses with commensurate carrier frequencies. It is demonstrated that the broad bandwidth radiation can be generated in the process and that its spectrum can be significantly enhanced by tailoring the laser field. A special emphasis is put on analyzing temporal properties of generated radiation. Full article

The RIN of an InAs/InP(113)B quantum-dot laser for direct- and cascade-relaxation models is investigated under the gain-switching condition via the application of an optical Gaussian pulse to an excited state. A new method is proposed to obtain RIN curves by eliminating the cross-correlation between noise sources. In this way, the noise sources are described independently and simulated with independent white Gaussian random variables. The results revealed that the RIN spectrum of both models was the same, apart from the fact that the cascade-relaxation model generated somewhat shorter pulses than the direct-relaxation model. Nevertheless, the direct-relaxation model had a lower RIN than that of the cascade-relaxation model. Excited- and ground-state carrier noises strongly affected the RIN spectrum, whereas the wetting-layer carrier noise had a negligible effect. In addition, the capture and escape times significantly affected the RIN spectrum. The output pulses had a long pulse width for both models due to the long pulse width of the ground-state photons. Nevertheless, applying an optical Gaussian pulse to an excited state reduced the RIN of both models and produced narrower gain-switched output pulses. Full article