Microwave induced breakdown spectroscopy: Insights into plasma dynamics and spectrum analysis.

We investigate the generation of MeV x-rays using the Advanced Radiography Capability laser system at the National Ignition Facility using 1, 10, and 38 ps pulse durations, with laser energies reaching up to 4 kJ and using compound parabolic concentrators. Hydrodynamic simulations using up-to-date measurements of the contrast of the ARC laser are conducted, allowing us to employ an electron scaling model that incorporates scale length and pulse duration, which aligns closely with the observed temperature distributions. Comparable x-ray sources, in terms of dose, are generated when using a 10 ps pulse duration with 2.4 kJ at ∼1.9 ± 0.4 × 1018 W/cm2 and when using a 38 ps pulse duration with 4 kJ at 9.9 ± 0.4 × 1017 W/cm2, both achieving ∼16 rad in air at 1 m for x-ray energies > 0.5 MeV. Radiographs performed on the laser “line-of-sight” show significant improvements in image quality than radiographs performed at 65 degrees to the laser axis. We verify the radiography performance using Monte Carlo Simulations.

Numerical simulation and experimental investigation of laser pulse duration effects on Ni/SiC ohmic contacts during ultraviolet laser annealing

Thermoluminescent response of Zn-modified titanium dioxide thin films subjected to continuous or pulsed ultraviolet radiation.

Pulse duration dependence of material response in ultrafast laser-induced surface-penetrating nanovoids in fused silica

For on-chip learning, ideal weight storage elements should have scalability, data retention, symmetry and linear conductance modulation, and weight fine-tuning capabilities. In this study, memristors are fabricated by employing cyano-based ultrathin copolymer films (<10nm) using 2-cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) as functional monomers via an initiated chemical vapor deposition (iCVD) process, optimized to serve as a high-performance device for convolutional neural networks (CNNs). The device achieves highly linear, symmetric, and multi-level conductance modulation through precise control of polymer composition engineering. The switching characteristics and filament formation are controlled by varying the ratio of CEA and DEGDVE. In addition, the reliability and operation mechanism of the device are studied through non-invasive observation of the conducting filament dynamics via electrical manipulation using ramp pulse series (RPS). Finally, image classification tasks ares performed on high-resolution datasets such as Oxford 102 Flowers, Food-101, and Stanford Cars by varying pulse amplitudes and durations to simulate conductance modulation such as potentiation and depression of weights in memristors. Utilizing various networks such as VGG-X, ResNet-X, and DenseNet, the proposed system demonstrated robust performance, achieving up to 88.39% classification accuracy, validating the efficiency of the memristor-based CNN architecture in real-world AI applications.

Abstract Predicting the properties of electrons accelerated to relativistic energies via Laser Wakefield Acceleration is dependent on a wide range of parameters that are difficult to efficiently optimize. Such problems would benefit from the use of Bayesian optimization schemes, which if implemented correctly may efficiently find optimums in complex parameter spaces. By separating the laser wakefield mechanism into two stages, an initially higher density plasma of high Z gases may be used to inject higher charge while a low density homogeneous plasma can be used to efficiently accelerate electrons with the same laser pulse. However, the nonlinear relationship between the two stages makes the determination of optimal beam parameters difficult. We show that through the use of a Bayesian optimization process on 2.5D3V Particle-In-Cell simulations we are able to efficiently map out regions of interest across a wide variety of physical regimes while keeping down the computational costs of the parameter scan. Numerically modeling the two stage system, we varied the injection stage density profile and length and examined the impact on electron beam charge, energy spectrum, and emittance. We also examined the impact on the laser pulse itself with regards to the temporal pulse duration. Our analysis identified specific regions in the parameter space where variations in pulse propagation and injection processes significantly influenced the characteristics of the resulting electron beam. This approach enabled us to efficiently identify numerous physical regimes with options on how to tune the electron beam for various applications.

Objective: Focused ultrasound (FUS) with intravenously administered microbubbles (MBs) enables different therapeutic effects, e.g. localized opening of the blood-brain barrier (BBB). Acoustic activation of MBs under FUS induces mechanical effects-primarily stable or inertial cavitation - that can reversibly disrupt endothelial tight junctions without permanent tissue damage. MB acoustic emissions are widely used as indicators of cavitation activity and, by extension, treatment efficacy and safety. While some aspects of microbubble behavior under different exposure conditions are known, the overall influence of various parameter combinations on cavitation dose remains incompletely described.Approach: This study examined how MB concentration (0.0008-0.4% V/V), peak negative pressure (61.5-2600 kPa), pulse duration (95-952 μs), and effective sonication time affect cavitation activity in a flow setup. Cavitation was quantified as a cavitation dose which was divided into three types: stable harmonic (SCDhar), ultraharmonic (SCDultra), and broadband (ICD) emissions.Results: SCDharand ICD increased mostly monotonically with pressure and MB concentration, while SCDultrapeaked at intermediate values suggesting optimal parameters for the control of the ultrasound BBB opening procedure. Cavitation metrics showed 10% reproducibility. Critically, we found that for fixed effective sonication times, increasing the number of pulses led to significantly change the response of cavitation dose in time. To our knowledge, this relationship has not been studied before, change of pulse length was always related to effective sonication time. Our results suggests that pulse number is an important factor of how MB oscillate, introducing a potentially pivotal control parameter for therapeutic ultrasound.Significance: These findings provide new insights into MB dynamics and highlight pulse count as an underrecognized yet potentially important factor in protocol design. This perspective may inform refinements of FUS treatments, contributing to greater safety, consistency, and efficacy, and represents a step toward optimizing ultrasonic BBB opening strategies.

Laser-driven ion beams offer significant advantages over radio-frequency accelerated beams, making them particularly promising for biomedical applications. Key features include their ultrashort pulse duration, on the order of picoseconds, and high peak fluxes ranging from 10 11 to 10 13 particles per shot. These characteristics enable the delivery of ultrahigh dose rates, potentially reaching the FLASH therapy regime. The future implementation of laser-driven ion beams in clinical settings relies on the development of advanced focusing and beam transport systems capable of precisely controlling parameters such as energy range, beam focus, and dose distribution to meet stringent therapeutic requirements. However, the integration of ultrashort laser-driven ion beams into medical treatments presents challenges, particularly due to their broad energy spectrum and high angular divergence. We present 3D simulation-based studies investigating the focusing effects of different high-current solenoid configurations on laser-plasma-accelerated proton beams. To identify the optimal focusing solution, we designed, analyzed, and compared high-current solenoids of varying dimensions and shapes, both as stand-alone magnetic elements and as part of two-solenoid focusing systems. Our analysis focuses on magnetic fields between 6 and 9 T, generated by the high-current solenoids. The study considers a proton beam with an energy range from a few MeV to 20 MeV and an initial divergence of 21°. Results are evaluated in terms of collection efficiency, beam focusing position, and beam profile. The optimized beamline configuration was then used to assess the dose distribution in a cylindrical water target with a volume of 78 mm 3 by calculating the absorbed dose and dose delivery rates, demonstrating the potential of laser-plasma-accelerated proton beams for radiotherapy applications.

Energy harvesting-storage hybrid devices have garnered considerable attention as self rechargeable power sources for wireless and ubiquitous electronics. Triboelectric nanogenerators (TENGs), a common type of energy harvester, generate irregular alternating current (AC), posing a challenge for storing the generated electrical energy in energy storage systems that typically operate with direct current (DC)-based low frequency response. In this study, we propose a new strategy that leverages high-frequency response to develop efficient chargeable TENG-supercapacitor (SC) hybrid devices. The electrochemical interplay between the TENGs and SCs was also investigated as a function frequency characteristics of SCs (fSC) and the output pulse duration of TENGs (ΔtTENG), finding that increasing fSC∙ΔtTENG enhanced the charging efficiency of the TENG–SC hybrid devices. Based on this understanding, A high frequency SC was fabricated using hollow-structured MXene electrode materials, resulting in a twofold increase in the charging efficiency of the hybrid device compared to a conventional carbon-based SC. This study highlights the importance of frequency response design in developing efficient chargeable TENG–SC hybrid devices.

Doping generally introduces performance trade-offs in materials, yet overcoming this fundamental limitation remains crucial for advancing materials research. Bi2O2Se exhibits exceptional electronic properties as a promising semiconductor, yet its nonlinear optical response under low excitation intensities hinders its practical applications. Therefore, precise Sb3⁺ doping in Bi2O2Se (Bi1.9Sb0.1O2Se) is achieved for the first time via solid-state reaction and systematically studies its impact on the electronic structure and optical properties through first-principles calculations and experimental. The results reveal that Sb3⁺ substitution slightly reduces the bandgap without introducing defect states, and transient absorption spectroscopy further confirms prolonged carrier relaxation. At 1.5µm, the modulation depth from 8.8% to 10.1% while dramatically reducing the saturation intensity from 47.2 to 0.53kWcm- 2. This improvement is attributed to the stable linear absorption characteristics after doping, the synergistic effect between prolonged relaxation time and free-carrier-induced optical loss. In a mode-locking system, Bi1.9Sb0.1O2Se achieves a broader 3-dB and shorter pulse duration at substantially reduced pump intensities. This work achieves defect-free energy level optimization in Sb-doped Bi2O2Se, where the material's high carrier mobility is not only preserved but further enhanced, while the saturation intensity is declined by about two orders of magnitude, enabling a low-power, high-performance nonlinear photonic devices.

ABSTRACT Dispersion engineering has been instrumental in promoting, through intracavity pulse stretching, the generation of higher‐energy mode‐locked pulses. Such approach requires extra‐cavity compression and struggles to deliver bell‐shaped pulses. However, in the context of dissipative solitons, it is also possible to generate energetic, pedestal‐free pulses in the quasi‐absence of dispersive linear effects. We achieve the latter by tailoring picosecond pulses through spectral filtering, inspired by the recently reported energy‐managed soliton laser architecture. The present dispersion‐less energy‐managed mode‐locked fiber laser demonstrates remarkable flexibility in both pulse energy and duration. Its experimental validation, using standard telecom components in the telecom window, yields mode‐locked pulses of up to at a repetition rate of 1.9 MHz. We introduce an additional energy scaling by incorporating a few‐mode gain fiber to generate pulses featuring low spectral distortion.

Laser-based sectioning has emerged as a game-changing technique for high-precision and material-efficient processing of silicon carbide (SiC) wafers. However, the fundamental mechanisms behind ultrafast laser-induced subsurface modifications remain poorly understood. This study investigates ultrafast laser-induced internal modifications in semi-insulated SiC wafers, with a focus on the effects of laser pulse energy and duration. Raman spectroscopy revealed that the modified SiC structure comprises crystalline SiC, amorphous SiC, amorphous Si, and amorphous C. Thermal stress analysis revealed distinct crack propagation patterns that vary with laser parameters. Two scanning strategies and spacing configurations were analyzed to optimize the stripping of SiC wafers. An internal laser cross-scanning method is proposed, enabling successful delamination of 4-inch SiC wafers and delivering key improvements: (1) a 30% reduction in peeling stress, (2) a modified layer height of ∼25 µm, and (3) surface roughness below 7.3 µm. This technique preserves up to 90% of the material compared to conventional diamond wire sawing, offering remarkable gains in both precision and material efficiency.

Abstract Femtosecond mode‐locked lasers (MLLs) with hundreds of megahertz repetition rate are of broad interest due to the relatively large longitudinal mode interval. The performance of MLL is dominated by the active fiber, and candidates with both high gain and high compatibility with inactive silica fiber are urgently required. Herein, we propose and demonstrate an Er‐doped hybridized silicate glass fiber (EHSGF) for nonlinear polarization rotation‐based high‐repetition‐rate MLL. The fiber is derived from silica and hybridized with Y and Al elements, which enables providing a rich chemical environment for the active Er dopant. As a result, EHSGF with heavily doped Er 3+ ions and a high gain coefficient of 2 dB/cm can be realized. In addition, it exhibits excellent chemical affinity with the Si‐O, and the fiber can be directly fused with commercial silica fiber without a bridge component. We design and build a stable MLL device with a fundamental repetition rate up to 318.94 MHz by using only 9.5 cm EHSGF without any special integrated devices. The central wavelength is around 1565 nm with a 3 dB width of 32 nm, and the direct output pulse duration is 87 fs, which is close to the transform limit. The measured root mean square power fluctuation remains below 0.039% during continuous 12‐h operation. We believe this research provides a new strategy for the development of highly doped Er‐doped fibers and high‐repetition‐rate laser systems.

Abstract Organic semiconductors are emerging as a promising class of photovoltaic materials for neural interfaces, offering high power conversion, mechanical flexibility, biocompatibility, and tunable optoelectronic properties. In this study, the application of a D18:Y6‐based organic photovoltaic (OPV) electrode is investigated for subretinal stimulation in a model of retinal degeneration. It is demonstrated that OPV devices can be engineered to electrically stimulate the retina via network‐mediated pathways, in a manner comparable to established neurostimulation approaches. The presented OPV electrodes reliably activate retinal ganglion cells, eliciting consistent spike responses to light pulses within the near‐infrared range. The stimulation onset, spike latency, and response profiles suggest effective faradaic charge injection as a key mechanism for neuronal activation, particularly for longer pulse durations. Moreover, it is shown that both light intensity and pulse duration can be used to finely tune the neural response, offering a high degree of control over retinal ganglion cell activation. Finally, it is proven that D18:Y6 blend is biocompatible in vitro when in direct contact with human induced pluripotent stem cell (iPSC)‐derived retinal organoids and mouse explants. These results validate the photo‐electrical performance and biocompatibility of D18:Y6 OPVs and position them as a viable candidate for next‐generation, minimally invasive retinal prosthetics.

High energy, long pulse duration and high repetition rate 351 nm ultraviolet laser from intracavity frequency-tripling of a Nd:YLF laser

Comprehensive evaluation of angiography Equipment: Ensuring precision and compliance in high-precision medical procedures.

We present a numerical model of a plasma maser—an ultra-wideband generator of microwave radiation operating at frequencies varying from 15 to 8 GHz during a single pulse, with output power reaching up to 1 GW. The relativistic high-current electron beam parameters—550 keV energy, 80 ns pulse duration, and 14 kA current—approximate the performance of existing accelerators. In contrast to earlier implementations, which utilized beam currents around 2 kA, our model fully exploits the accelerator's potential. The results demonstrate both the feasibility and implications of operating plasma masers with significantly higher currents, including the impact on radiation frequency dynamics and beam–plasma interactions.

The standard Port Wine Stains (PWS) treatment involves using single pulse high fluence (SPHF) laser therapy, which often leads to discomfort and requires multiple sessions. According to the Arrhenius theory, employing multiple pulses with low fluence (MPLF) that have lower peak power could potentially reduce pain while still achieving the therapeutic goals. This study aims to explore the potential of MPLF at 530 nm in achieving the desired clinical endpoints in treating PWS. Additionally, it seeks to validate the predictions of the Arrhenius theory regarding thermal denaturation against empirical data, utilizing established kinetic parameters. We evaluated vascular responses to SPHF and MPLF approaches using the chorioallantoic membrane (CAM) model and a 530 nm customized fiber laser. Vascular changes were observed with a digital microscope, and temperature was monitored with a thermal camera during irradiation through a 3 × 3 mm spot at 9-10 ms pulse durations, targeting stable coagulum and vessel collapse. First, we established the SPHF threshold, then applied MPLF at 20%-75% of this fluence with a pulse duration of 9-10 ms and a repetition rate of 0.1 or 0.2 Hz (corresponding to 1 pulse every 10 or 5 s, respectively). Additionally, we used the Arrhenius theory with specific kinetic parameters to predict and validate thermal damage. We observed that both SPHF and MPLF approaches effectively achieved clinical endpoints. Stable coagulum formation was successful at a fluence of 4.2 J/cm² with a pulse width of 10 ms under SPHF. Similarly, MPLF achieved stable coagulum at a lower fluence of 2.2 J/cm², with the thrombus forming after 16 pulses and enlarging by the 32nd pulse. Vessel collapse was also noted at a fluence of 10.8 J/cm² in the SPHF regime and at 5.9 J/cm² with MPLF, with early closure observed after the fourth pulse and completion by the sixteenth. Surface temperature measurements indicated a minor rise following laser exposure, which quickly returned to near baseline levels. Using two sets of activation energies, the Arrhenius model predicted the extent of vessel denaturation and informed the number of pulses required to reach the damage threshold, indicating a lower slope and thus easier damage accumulation with MPLF below the SPHF threshold. This study provides evidence that using MPLF laser treatment at 530 nm with fluences ranging from 50% to 70% of the SPHF threshold can effectively induce stable coagulum and vessel collapse within the CAM model while maintaining baseline temperatures.

Brain-wide hemodynamic responses to precise transcranial ultrasound neuromodulation.