Huge Recalcitrant Warts Treated with Pulse Dye Laser after Conventional Therapies and Others Destructive Physical Modalities Failed

Cutaneous infections with the human papilloma virus, despite being almost always asymptomatic, can induce slow-growing lesions knowed as warts that can remain subclinical for long periods of time. There are several therapeutical options namely keratolytics, retinoids, imiquimod, cryotherapy, electrosurgery, lasers and classic surgery, but none has antiviral effects. We describe the case of a patient with large warts located on the dorsal surface of the right hand, treated with cryotherapy, CO2 laser and topical imiquimod having either no clinical response or quick relapse. Treatment with PDL was started and after 13 sessions, the patient was without lesions, with a good cosmetic result and so far without relapse. This case report is relevant to us and deserves to be published because of the size of the lesions and the great response to PDL despite all the failures with the other treatments.

Uncovering gold nanoparticle synthesis using a microchip laser system through pulsed laser ablation in aqueous solution

The synthesis of gold nanoparticles(Au NPs)was carried out by utilising the pulsed laser ablation in liquids(PLAL)method with a microchip laser(MCL)system.This portable system features low power consumption and a giant-pulse laser.Aqueous solutions with and without the surfactant poly(N-vinyl-2-pyrrolidone)(PVP)were used for laser ablation of a bulk gold rod to achieve the successful formation of a colloidal solution of Au NPs.The gas bubbles formed by heating the aqueous medium around the surface of the gold target significantly reduced the efficiency of Au NP ablation.This effect was more pronounced and prolonged in high-viscosity solutions,hindering energy transfer from subsequent laser pulses to the target.Additionally,it was suggested that the chain length of PVP does not affect either the size of the Au NPs or the ablation efficiency.Videography experiments were conducted to explore the ablation mechanism employed by the MCL system.The relatively short pulse duration of the MCL system may contribute to the formation of NPs with consistent size,which were suppressed to grow in significantly smaller cavitation bubbles with short lifetimes.

Electrokinetic-mechanism of water and furfural oxidation on pulsed laser-interlaced Cu_(2)O and CoO on nickel foam

The electrocatalytic oxidation of biomass-derived furfural(FF)feedstocks into 2-furoic acid(FA)holds immense industrial potential in optics,cosmetics,polymers,and food.Herein,we fabricated Co O/Ni O/nickel foam(NF)and Cu_(2)O/Ni O/NF electrodes via in situ pulsed laser irradiation in liquids(PLIL)for the bifunctional electrocatalysis of oxygen evolution reaction(OER)and furfural oxidation reaction(FOR),respectively.Simultaneous oxidation of NF surface to NiO and deposition of CoO and/or Cu_(2)O on NF during PLIL offer distinct advantages for enhancing both the OER and FOR.CoO/NiO/NF electrocatalyst provides a consistently low overpotential of~359 m V(OER)at 10 m A/cm^(2),achieving the maximum FA yield(~16.37 m M)with 61.5%selectivity,79.5%carbon balance,and a remarkable Faradaic efficiency of~90.1%during 2 h of FOR at 1.43 V(vs.reversible hydrogen electrode).Mechanistic pathway via in situ electrochemical-Raman spectroscopy on CoO/NiO/NF reveals the involvement of phase transition intermediates(NiOOH and CoOOH)as surface-active centers during electrochemical oxidation.The carbonyl carbon in FF is attacked by hydroxyl groups to form unstable hydrates that subsequently undergo further oxidation to yield FA products.This method holds promise for large-scale applications,enabling simultaneous production of renewable building materials and fuel.

On the generation of high-quality Nyquist pulses in mode-locked fiber lasers

Nyquist pulses have wide applications in many areas,from electronics to optics.Mode-locked lasers are ideal platforms to generate such pulses.However,how to generate high-quality Nyquist pulses in mode-locked lasers remains elusive.We address this problem by managing different physical effects in mode-locked fiber lasers through extensive numerical simulations.We find that net dispersion,linear loss,gain and filter shaping can affect the quality of Nyquist pulses significantly.We also demonstrate that Nyquist pulses experience similariton shaping due to the nonlinear attractor effect in the gain medium.Our work may contribute to the design of Nyquist pulse sources and enrich the understanding of pulse shaping dynamics in mode-locked lasers.

Electromagnetic pulses produced by a picosecond laser interacting with solid targets

A high-power laser ablating solid targets induces giant electromagnetic pulses(EMPs),which are intimately pertinent to laser parameters,such as energy and pulse width.In this study,we reveal the features of EMPs generated from a picosecond(ps)laser irradiating solid targets at the SG-Ⅱpicosecond petawatt(PSPW)laser facility.The laser energy and pulse,as well as target material and thickness,show determinative effects on the EMPs’amplitude.More intense EMPs are detected behind targets compared to those at the other three positions,and the EMP amplitude decreases from 90.09 kV/m to 17.8 kV/m with the gold target thickness increasing from 10μm to 20μm,which is suppressed when the laser pulse width is enlarged.The results are expected to provide more insight into EMPs produced by ps lasers coupling with targets and lay the foundation for an effective EMP shielding design in high-power laser infrastructures.

Efficient guiding and focusing of intense laser pulse using periodic thin slits

Slits have been widely used in laser-plasma interactions as plasma optical components for generating high-harmonic light and controlling laser-driven particle beams.Here,we propose and demonstrate that periodic thin slits can be regarded as a new breed of optical elements for efficient focusing and guiding of intense laser pulse.The fundamental physics of intense laser interaction with thin slits is studied,and it is revealed that relativistic effects can lead to enhanced laser focusing far beyond the pure diffractive focusing regime.In addition,the interaction of an intense laser pulse with periodic thin slits makes it feasible to achieve multifold enhancement in both laser intensity and energy transfer efficiency compared with conventional waveguides.These results provide a novel method for manipulating ultra-intense laser pulses and should be of interest for many laser-based applications.

Generation and regulation of electromagnetic pulses generated by femtosecond lasers interacting with multitargets

Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.

Collision off-axis position dependence of relativistic nonlinear Thomson inverse scattering of an excited electron in a tightly focused circular polarized laser pulse

This paper presents a novel view of the impact of electron collision off-axis positions on the dynamic properties and relativistic nonlinear Thomson inverse scattering of excited electrons within tightly focused, circularly polarized laser pulses of varying intensities. We examine the effects of the transverse ponderomotive force, specifically how the deviation angle and speed of electron motion are affected by the initial off-axis position of the electron and the peak amplitude of the laser pulse. When the laser pulse intensity is low, an increase in the electron's initial off-axis distance results in reduced spatial radiation power, improved collimation, super-continuum phenomena generation, red-shifting of the spectrum's harmonic peak, and significant symmetry in the radiation radial direction. However, in contradiction to conventional understandings,when the laser pulse intensity is relatively high, the properties of the relativistic nonlinear Thomson inverse scattering of the electron deviate from the central axis, changing direction in opposition to the aforementioned effects. After reaching a peak, these properties then shift again, aligning with the previous direction. The complex interplay of these effects suggests a greater nuance and intricacy in the relationship between laser pulse intensity, electron position, and scattering properties than previously thought.

Harmonic splitting phenomenon of bright-dark pulse pairs in a passive mode-locked Thulium-Holmium co-doped fiber laser

This study reports a passive mode-locked Thulium-Holmium co-doped fiber laser featuring a figure-9 shaped resonator structure.The laser utilizes a nonlinear amplifying loop mirror(NALM)as the mode-locking device.By increasing pump power,the laser’s output evolution was experimentally observed,showing that bright-dark pulse pairs first split into double pulses and then into a second harmonic state.Additionally,the time intervals between bright and dark pulses and between double pulses increased with higher pump power.The RF spectrum of the bright-dark pulse pairs exhibited envelope modulation,with a modulation frequency approximately equal to the reciprocal of the time interval between bright and dark pulses.When the pump power increased from 0.46 W to 0.72 W,the reciprocal of the modulation frequency showed a linear growth trend.These findings contribute to understanding the evolution patterns of bright-dark pulse pairs in passive mode-locked fiber lasers.

Pulsed laser interference patterning of transition-metal carbides for stable alkaline water electrolysis kinetics

We investigated the role of metal atomization and solvent decomposition into reductive species and carbon clusters in the phase formation of transition-metal carbides(TMCs;namely,Co_(3)C,Fe_(3)C,TiC,and MoC)by pulsed laser ablation of Co,Fe,Ti,and Mo metals in acetone.The interaction between carbon s-p-orbitals and metal d-orbitals causes a redistribution of valence structure through charge transfer,leading to the formation of surface defects as observed by X-ray photoelectron spectroscopy.These defects influence the evolved TMCs,making them effective for hydrogen and oxygen evolution reactions(HER and OER)in an alkaline medium.Co_(3)C with more oxygen affinity promoted CoO(OH)intermediates,and the electrochemical surface oxidation to Co_(3)O_(4)was captured via in situ/operando electrochemical Raman probes,increasing the number of active sites for OER activity.MoC with more d-vacancies exhibits strong hydrogen binding,promoting HER kinetics,whereas Fe_(3)C and TiC with more defect states to trap charge carriers may hinder both OER and HER activities.The results show that the assembled membrane-less electrolyzer with Co_(3)C∥Co_(3)C and MoC∥MoC electrodes requires~2.01 and 1.99 V,respectively,to deliver a 10 mA cm−2 with excellent electrochemical and structural stability.In addition,the ascertained pulsed laser synthesis mechanism and unit-cell packing relations will open up sustainable pathways for obtaining highly stable electrocatalysts for electrolyzers.

Short Pulse Width and High Peak Power 457 nm Deep Blue Laser with V-Type Cavity

An intracavity frequency doubling acousto-optically Q-switched Neodymium-doped Yttrium Orthvanadate (Nd:YVO4) 457 nm blue laser by employing a three-mirror folded cavity was demonstrated. With the incident pump power of 40.4 W, the maximum average output power of 439 mW 457 nm laser, and the minimum pulse duration of 86.14 ns and the maximum peak power of 510 W were achieved at 10 kHz. The M2 factors are 1.23 and 1.61 in X and Y directions, respectively. The power stability in two hours is better than 2%.

FLASHLAMP- PUMPED PULSED DYE LASER IN TREATMENT OF PORT- WINE STAINS

To assess the effectiveness of the flashlamp- pumped pulsed dye laser (Photogeneca V, Synosure Corp, Boston, United States) in the treatment of port- wine stains. Methods. One hundred and ninety- four consecutive patients with port- wine stains were treated with a flashlamp- pumped pulsed dye laser in Peking Union Medical College Hospital from January 1998 to August 1999. Results. Of 194 patients who completed treatment, 56.2％ had more than 60％ fading of the lesion and only 6.7％ had less than 20％ fading. An average of 3.6 treatments were needed to achieve more than 60％ fading. The response was better in children than in adults, although the difference was not significant. Pigmentary change (usually transient) occurred in 3.1％ of patients. Conclusions. This study confirms the efficacy of the flashlamp- pumped pulsed dye laser in the treatment of port- wine stains in children and adults.

Early Pulsed Dye Laser Treatment for Infantile Hemangiomas: An Open Study for 50 Japanese Infancies

Infantile hemangiomas, occurring at birth or during the first weeks of life, are benign vascular tumors with an initial proliferative phase and a later involutional phase. The massive proliferation on the key regions and unpredicted regression may threaten?life. Thus, early management of infantile hemangiomas is necessary for affected infancies. Recent studies showed that propranolol for infantile hemangiomas had high efficacy for disappearance or reduction of infantile hemangiomas. However, a most recent study demonstrated existence of propranolol-resistant infantile hemangiomas. Therefore, we retrospectively evaluated efficacy of established early pulsed dye laser treatment for infantile hemangiomas in the 50 Japanese infancies which were applied in the period from 2000 to 2005, because our series included from the plaque subtype to the more proliferative tumor subtype. High efficacy in both subtypes suggests that early pulsed dye laser treatment can still be included as the first option for the mixed type of infantile hemangiomas and that pulsed dye laser treatment may be useful as the second line for the propranolol-resistant mixed type of infantile hemangiomas.

Measurement of spatiotemporal characteristics of femtosecond laser pulses by a modified single-shot autocorrelation

To overcome the shortcomings of the single-shot autocorrelation SSA where only one pulse width is obtained when the SSA is applied to measure the pulse width of ultrashort laser pulses a modified SSA for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions is proposed. The spatiotemporal characteristics of femtosecond laser pulses output from the Ti sapphire regenerative amplifier system are experimentally measured by the proposed method. It was found that the complex spatial characteristics are measured accurately.The pulse widths at different spatial positions are various which obey the Gaussian distribution.The pulse width at the same spatial position becomes narrow with the increase in input average power when femtosecond laser pulses pass through a carbon disulfide CS2 nonlinear medium.The experimental results verify that the proposed method is valid for measuring the spatiotemporal characteristics of ultrashort laser pulses at different spatial positions.

Grain refining in weld metal using short-pulsed laser ablation during CW laser welding of 2024-T3 aluminum alloy

The 2024 aluminum alloy is used extensively in the aircraft and aerospace industries because of its excellent mechanical properties.However,the weldability of 2024 aluminum alloy is generally low because it contains a high number of solutes,such as copper(Cu),magnesium(Mg),and manganese(Mn),causing solidification cracking.If high speed welding of 2024 aluminum alloy without the use of filler is achieved,the applicability of 2024 aluminum alloys will expand.Grain refining is one of the methods used to prevent solidification cracking in weld metal,although it has never been achieved for high-speed laser welding of 2024 aluminum alloy without filler.Here,we propose a short-pulsed,laser-induced,grain-refining method during continuous wave laser welding without filler.Bead-on-plate welding was performed on a 2024-T3 aluminum alloy at a welding speed of 1 m min−1 with a single mode fiber laser at a wavelength of 1070 nm and power of 1 kW.Areas in and around the molten pool were irradiated with nanosecond laser pulses at a wavelength of 1064 nm,pulse width of 10 ns,and pulse energy of 430 mJ.The grain-refinement effect was confirmed when laser pulses were irradiated on the molten pool.The grain-refinement region was formed in a semicircular shape along the solid–liquid interface.Results of the vertical section indicate that the grain-refinement region reached a depth of 1 mm along the solid–liquid interface.The Vickers hardness test results demonstrated that the hardness increased as a result of grain refinement and that the progress of solidification cracking was suppressed in the grain refinement region.

Microstructure and mechanical properties of pulsed laser welded Al/steel dissimilar joint

Pulsed laser welding was used in joining pure aluminum to stainless steel in a lap joint configuration. It is found that the mechanical properties of the laser joints were closely correlated with the bead geometry, i.e., penetration depth. In order to study the correlation, two typical laser welds with different penetration depths were analyzed. In high penetration depth (354 μm) joint, Al-rich Fe?Al IMCs with microcracks were formed at the Al/fusion zone (FZ) interface. The joint strength was found to be (27.2±1.7) N/mm and three failure modes were observed near the Al/FZ interface. In low penetration depth (108 μm) joint, Fe-rich Fe?Al IMCs without any defect were formed at the Al/FZ interface. The joint strength was found to be (46.2±1.9) N/mm and one failure mode was observed across the FZ.

A New Synthetical Model of High-Power Pulsed Laser Ablation

We develop a new synthetical model of high-power pulsed laser ablation,which considers the dynamicabsorptance,vaporization,and plasma shielding.And the corresponding heat conduction equations with the initial andboundary conditions are given.The numerical solutions are obtained under the reasonable technical parameter condi-tions by taking YBa_2Cu_3O_7 target for example.The space-dependence and time-dependence of temperature in targetat a certain laser fluence are presented,then,the transmitted intensity through plasma plume,space-dependence oftemperature and ablation rate for different laser fluences are significantly analyzed.As a result,the satisfactorily goodagreement between our numerical results and experimental results indicates that the influences of the dynamic absorp-tance,vaporization,and plasma shielding cannot be neglected.Taking all the three mechanisms above simultaneouslyinto account for the first time,we cause the present model to be more practical.

High power terahertz pulses generated in intense laser-plasma interactions

Terahertz （THz） radiation has attracted much attention due to its wide potential applications. Though radiation can be generated with various ways, it is still a big challenge to obtain strong tabletop sources. Plasma, with the advantage of no damage limit, is a promising medium to generate strong THz radiation. This review reports recent advances on strong THz radiation generation from low-density gases and high-density solid targets at different laser intensities.

Electron acceleration by tightly focused radially polarized few-cycle laser pulses

Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. The resulting field distribution is significantly different from that based on the paraxial approximation for pulses with either small or large beam diameters. We compare the electron accelerations obtained with the two solutions and find that the energy gain obtained with our new solution is usually much larger than that with the paraxial approximation solution.

Noise-like rectangular pulses in a mode-locked double-clad Er:Yb laser with a record pulse energy

Generation of noise-like rectangular pulse was investigated systematically in an Er–Yb co-doped fiber laser based on an intra-cavity coupler with different coupling ratios.When the coupling ratio was 5/95,stable mode-locked pulses could be obtained with the pulse packet duration tunable from 4.86 ns to 80 ns.The repetition frequency was 1.186 MHz with the output spectrum centered at 1.6μm.The average output power and single pulse energy reached a record 1.43 W and1.21μJ,respectively.Pulse characteristics under different coupling ratios(5/95,10/90,20/80,30/70,40/60)were also presented and discussed.