Search

Aims Pulsed field ablation (PFA) is emerging as a non-thermal, tissue-specific technique for pulmonary vein isolation (PVI) in atrial fibrillation therapy. This pre-clinical study aims to investigate the feasibility and safety of PVI using a novel PFA system including a nanosecond-scale PFA generator, a novel lotos PFA catheter, and a customized 12 Fr steerable sheath. Methods and results A total of 11 Yorkshire swine were included in this study, with 4 in the acute cohort and 7 in the chronic cohort. Under general anaesthesia, transseptal puncture and pulmonary vein (PV) angiography was initially performed. The PFA catheter was navigated to position at the right and left PV antrum after the electroanatomic reconstruction of the left atrium. Biphasic PFA applications were performed on PVs in both the spindle-shaped and the lotos-shaped poses. Pulmonary vein isolation and PFA-associated safety were assessed 30 min after ablation in both cohorts and 30 days later in the chronic cohort. Detailed necropsy and histopathology were performed. Additional intracardiac echocardiography and coronary angiogram were evaluated for safety. All target PVs (n = 20) were successfully isolated on the first attempt. No spasm of coronary artery or microbubble was seen during the procedure. Eleven of 12 PVs (91.6%) remained in isolation at the 30-day invasive study. No evidence of PV stenosis was observed in any targets. However, transient diaphragm capture occurred in 17.6%. Histopathological examinations showed no evidence of collateral injury. Conclusion This study provides scientific evidence demonstrating the safety and efficacy of the novel PFA catheter and system for single-shot PVI, which shows great potential. [ABSTRACT FROM AUTHOR]

Under water laser ablation is a surface texturization method used to form micrometer-sized surface structures. Plasma confinement and cavitation bubble evolution play a critical role during the ablation process and their influence on material removal is strongly tied to liquid layer thickness. To influence the effects of these processes, such that material removal is at its maximum, an optimal layer thickness was found for various laser parameters. Specifically, for nanosecond pulsed laser ablation of stainless steel, however, the relation between layer thickness and volume removal is still unknown. Here, we show the relation between water layer thickness and removed material volume for a nanosecond pulsed laser. Results reveal that volume removal is at its maximum for a 1 mm water layer and drops by a factor of 2 when the layer thickness is increased to 2 mm. A further increase of layer thickness to 3 up to 10 mm shows a negligible effect on volume removal and removed volume amounts are shown to be similar to those obtained in ambient air in this water layer thickness range. This trend echo's results obtained for nanosecond pulsed silicon ablation. The obtained results identify processing conditions which allow for faster and therefore more cost efficient texturization of stainless steel surfaces in the future. [ABSTRACT FROM AUTHOR]

With the increasing processing power of micro-electronic components and increasing spatial limitations, ensuring sufficient heat dissipation has become a crucial task. This work presents a microscopic approach to increasing the surface area through periodic surface structures. Microstructures with a periodic distance of 8.5 µm are fabricated via Direct Laser Interference Patterning (DLIP) on stainless steel plates with a nanosecond-pulsed infrared laser and are characterized by their developed interfacial area ratio. The optimal structuring parameters for increasing the surface area were investigated, reaching peak-to-valley depths up to 12.8 µm and increasing surface area by up to 394%. Heat dissipation in a natural convection environment was estimated by measuring the output voltage of a Peltier element mounted between a hot plate and a textured sample. The resulting increase in output voltage compared to an unstructured sample was correlated to the structure depth and developed interfacial area ratio, finding a maximum increase of 51.4%. Moreover, it was shown that the output voltage correlated well with the structure depth and surface area. [ABSTRACT FROM AUTHOR]

Calcium electroporation (CaEP) is an innovative approach to treating cancer, involving the internalization of supraphysiological amounts of calcium through electroporation, which leads to cell death. CaEP enables the replacement of chemotherapeutics (e.g., bleomycin). Here, we present a standard microsecond (μsCaEP) and novel high-frequency nanosecond protocols for calcium electroporation (nsCaEP) for the elimination of carcinoma tumors in C57BL/6J mice. We show the efficacy of CaEP in eliminating tumors and increasing their survival rates in vivo. The antitumor immune response after the treatment was observed by investigating immune cell populations in tumors, spleens, lymph nodes, and blood, as well as assessing antitumor antibodies. CaEP treatment resulted in an increased percentage of CD4+ and CD8+ central memory T cells and decreased splenic myeloid-derived suppressor cells (MDSC). Moreover, increased levels of antitumor IgG antibodies after CaEP treatment were detected. The experimental results demonstrated that the administration of CaEP led to tumor growth delay, increased survival rates, and stimulated immune response, indicating a potential synergistic relationship between CaEP and immunotherapy. [ABSTRACT FROM AUTHOR]

Building upon recent advances in GaSb-based diode lasers and Er-doped fluoride fibre technologies, this article demonstrates for the first time the fibre-based amplification of mid-infrared diode lasers in the wavelength range around 2.78 $\mu$m. The laser setup consists of a GaSb-based diode laser and a single-stage Er-doped fibre amplifier. Amplification is investigated for continuous wave (CW) and ns-pulsed input signals, generated by gain-modulation of the GaSb-based seed lasers. The experimental results include the demonstration of output powers up to 0.9 W, pulse durations as short as 20 ns, and pulse repetition rates up to 1 MHz. Additionally, the amplification of commercial and custom-made GaSb-based seed lasers is compared and the impact of different fibre end-cap materials on laser performance is analysed.

Background and Objectives: This feasibility study describes the effects of Nano‐pulse stimulation™ (NPS™) technology using the CellFX™ System on acne vulgaris of the back with the objectives of demonstrating safety and effectiveness. The CellFX System applies nanosecond pulses of electrical energy to induce highly localized regulated cell death (RCD) in the cellular structures of the targeted zone with no thermal effect on the tissue and negligible effects on surrounding non‐cellular components. Study Design/Materials and Methods: Seventeen subjects were enrolled at two sites with thirteen subjects completing treatment. Three 7 X 7 cm regions containing at least five bacne lesions each were identified, one region treated with the CellFX across three treatment sessions, the second region treated as a sham using microneedle tip placement without delivering energy, and the third as an untreated control. Results: CellFX‐treated areas showed an average reduction of acne lesions of 82% by 90 days post‐last procedure. Acne improvement was observed in 100% of CellFX‐treated regions compared to 39% improvement in Sham regions and 31% improvement in the control regions. The most common skin effects were erythema and hyperpigmentation observed in 23% and 92% of the subjects, respectively, at the last timepoint. No serious adverse events were reported. Conclusions: CellFX is a safe and effective procedure for clearing back acne. [ABSTRACT FROM AUTHOR]

Phosphate exists concurrently in multiple waste streams. Embedded nickel oxide in polyvinyl alcohol (NiO/PVA) was doped by silver nanoparticles (Ag) to generate an Ag-doped NiO/PVA nanocomposite structure prepared by multiple laser ablation process technique for removing phosphate. Different techniques were used to characterize the physicochemical properties of the substance. The characterization results of the prepared nanocomposites showed that NiO and Ag were successfully integrated into the PVA structure. They confirmed the production of hybrid nanocomposites by a reduction in the peak height due to intramolecular and intermolecular interactions with Ag nanoparticles from Raman spectra. Also, the shift in the absorbance transition characteristic and the appearance of vibrational motions of NiO and Ag confirmed the successful interaction between PVA, Ag, and NiO. After that, in the adsorption study, the most important aspect of the investigation was a series of phosphate adsorption tests from aqueous solutions, which showed that the efficiency of the adsorption process is dependent on the concentrations of the adsorbate and adsorbent, the pH, the reaction time, and the temperature. The results indicate that the current Ag-doped NiO/PVA nanocomposite adsorbent has the capacity to control phosphorus contamination in water.

In this work, a unified numerical model is used to determine the melting thresholds and to investigate the early stages of melting of several crystalline semiconductors (Si, Ge, GaAs, CdTe and InP) irradiated by nanosecond laser pulses. A molten fraction approach is used for continuous transition over the melting point. The results are compared with previously published theoretical and experimental data. A survey on the thermophysical and optical properties of the selected materials has been carried out to gather the most relevant data on temperature dependent properties for the solid and liquid states of these semiconductors where such data are available. A generalization of the obtained results is established that enables evaluation of the melting thresholds for different semiconductors based on their properties and irradiation conditions (laser wavelength, pulse duration). [ABSTRACT FROM AUTHOR]

Nanosecond laser impulsive heating is used to generate a liquid→gas phase transition that performs mechanical work. A simple laser flyer apparatus is designed where a metal plate is placed on top of a variable volume of liquid. When a high-energy nanosecond laser pulse impacts the bottom of the plate, explosive vaporization of the liquid propels it upward. The initial velocity of the plate, and thus its kinetic energy, is measured as a function of several parameters, including liquid volume, laser wavelength, pulse energy, and chemical composition of the liquid. Light-to-kinetic energy conversion efficiencies that approach 2% are measured. Although surface discoloration of the metal is observed, there was no measurable decrease in the initial velocity even after 200 cycles. For protic liquids like water and ethylene glycol, the initial velocity is independent of the chemical composition of the liquid, possibly due to the contribution of exothermic oxidative reactions at high temperatures. For alkane liquids, the initial velocity decreases with increasing molecular weight, consistent with a simple model that relates it to physical properties like the heat of vaporization. The results suggest that nanosecond pulsed laser heating for liquid→gas actuation may be a relatively efficient way to transform photons into mechanical energy. [ABSTRACT FROM AUTHOR]

Consumption of fossil fuels has led to yearly increases in emissions of CO2, a main component of the greenhouse gases that contribute to global warming. As such, methods to reduce CO2 emissions and treat the emitted CO2 are being researched around the world. One method of interest in treating CO2 is the use of non-thermal equilibrium plasma, which is low in cost and highly efficient. Nanosecond (NS) pulsed power generators with very short voltage durations of 5 ns have recently been developed. Such power generators feature minimal loss of heat and high electron energy. This study examined the characteristics of NS pulsed discharges when used to convert CO2 in order to determine its decomposition and conversion efficiency and compare it with other discharge methods. The effects on the CO2 conversion rate of changing the diameter of the central wire electrode and adding Ar were investigated. It was confirmed that the wire diameter of the central electrode has a significant effect on CO2 decomposition performance because it changes the nature of the discharge itself. A larger central electrode diameter is suitable for higher CO2 conversion rates The addition of Ar had a minimal effect on decomposition performance. A maximum conversion rate of 19.2 % was achieved by NS pulsed discharge, indicating the possibility of contributing to the reduction of CO2. [ABSTRACT FROM AUTHOR]

Simple Summary: Standard microsecond electrochemotherapy (μsECT) is used in clinical trials for the elimination of tumours, while the first studies on nanosecond electrochemotherapy (nsECT) only started to appear recently. Nanosecond pulses enable more homogeneous treatment and better control of pulse burst energy, and thus the whole field of electroporation is moving towards the shorter pulse range. In order to ensure a full anticancer response and potentially prevent any metastases, the immunomodulatory effects should also be induced. Therefore, in this work, we used nsECT protocols based on kHz and MHz pulse bursts and characterized the response of the immune system to the novel modality of nano-electrochemotherapy. The results of this study are useful for the development of effective anticancer treatment strategies based on high frequency nanosecond electric fields. In this work, a time-dependent and time-independent study on bleomycin-based high-frequency nsECT (3.5 kV/cm × 200 pulses) for the elimination of LLC1 tumours in C57BL/6J mice is performed. We show the efficiency of nsECT (200 ns and 700 ns delivered at 1 kHz and 1 MHz) for the elimination of tumours in mice and increase of their survival. The dynamics of the immunomodulatory effects were observed after electrochemotherapy by investigating immune cell populations and antitumour antibodies at different timepoints after the treatment. ECT treatment resulted in an increased percentage of CD4+ T, splenic memory B and tumour-associated dendritic cell subsets. Moreover, increased levels of antitumour IgG antibodies after ECT treatment were detected. Based on the time-dependent study results, nsECT treatment upregulated PD 1 expression on splenic CD4+ Tr1 cells, increased the expansion of splenic CD8+ T, CD4+CD8+ T, plasma cells and the proportion of tumour-associated pro inflammatory macrophages. The Lin− population of immune cells that was increased in the spleens and tumour after nsECT was identified. It was shown that nsECT prolonged survival of the treated mice and induced significant changes in the immune system, which shows a promising alliance of nanosecond electrochemotherapy and immunotherapy. [ABSTRACT FROM AUTHOR]

With rising prevalence of bone and skeletal diseases around the world, combatting implant failure through novel approaches has become a growing area of research. A novel way to produce tailored implants is additive manufacturing, which offers unprecedented design flexibility. On the other hand, the osseointegration of such implants can be optimized by applying periodic micro-textures on the surface, using laser-based techniques. In particular, the technique of Direct Laser Interference Patterning (DLIP) offers both high throughput and the possibility to produce structures with small feature sizes. In this work, DLIP is applied to produce line-like micro textures on additively manufactured Ti-13Nb-13Zr parts. Using different solid-state lasers, the effect of pulse durations in the nanosecond to femtosecond regime and laser wavelengths from the ultraviolet to near infrared spectrum on the micro texture topography is reported. For each wavelength and pulse duration, laser parameters are varied systematically. The surface topography of the specimens is characterized through scanningelectron microscopy, and surface roughness is measured with confocal microscopy. Interaction with nanosecond pulses is characterized by melting, resulting in mostly smooth textures, whereas picosecond and femtosecond pulses produce hierarchical textures with laser-induced periodic surface structures. [ABSTRACT FROM AUTHOR]

We investigate the gain bandwidth and wavelength-tuning range of an erbium-doped fluoride fibre amplifier. The presented experimental setup consisted of a widely wavelength-tunable optical parametric oscillator (OPO), which was amplified in a single-stage Er-doped fluoride fibre amplifier. The OPO laser provided seed pulses with a pulse width of 5.2 ns and a repetition rate of 10 kHz. The fibre section consisted of 2.2 m of double-clad, single-mode fibre with a doping concentration of 7 mol%. Wavelength-tuning was analysed at gain values of up to 26 dB and amplified pulse energies of up to 37.4 $\mu \mathrm{J}$. Using this setup, we demonstrate continuous wavelength tuning of more than 100 nm, covering the wavelength range from 2712 nm to 2818 nm. [ABSTRACT FROM AUTHOR]

In this study, nanosecond-pulse lasing was achieved using a vertical-external-cavity surface-emitting laser (VECSEL) with only a single gain chip. A simple linear-cavity setup was used for the VECSEL, and pulsed lasing with a pulse width of ∼9 ns and a repetition frequency of ∼54 MHz was achieved. Dual-wavelength lasing at 974 and 978 nm was observed. The average output power during pulsed operation exceeded 100 mW. As the pumping power was increased, the laser output power could be switched off. However, stable dual-wavelength emission was maintained. The maximum output power under dual-wavelength operation could reach 455 mW.

We investigate the gain bandwidth and wavelength-tuning range of an erbium-doped fluoride fibre amplifier. The presented experimental setup consisted of a widely wavelength-tunable optical parametric oscillator (OPO), which was amplified in a single-stage Er-doped fluoride fibre amplifier. The OPO laser provided seed pulses with a pulse width of 5.2 ns and a repetition rate of 10 kHz. The fibre section consisted of 2.2 m of double-clad, single-mode fibre with a doping concentration of 7 mol%. Wavelength-tuning was analysed at gain values of up to 26 dB and amplified pulse energies of up to 37.4 $\mu \mathrm{J}$. Using this setup, we demonstrate continuous wavelength tuning of more than 100 nm, covering the wavelength range from 2712 nm to 2818 nm.

In this research, we aimed to investigate the linear and non-linear optical properties of Ag-La 2 (MoO 4) 3 @RGO nanocomposites. For this purpose, Graphene Oxide (GO) was synthesized by Modified Hummer's method after which GO was chemically reduced to Reduced graphene oxide (RGO). The nanocomposite Ag-doped La 2 (MoO 4) 3 is prepared by a simple and facile co-precipitation method. The prepared nanocomposite was characterized by Fourier transform infrared (FTIR), Ultraviolet-Visible (UV-Vis) absorption, X-ray diffraction (XRD), Scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDX). XRD and EDX analysis indicated the reduction of GO and successful synthesis of Ag-doped La 2 (MoO 4) 3 nanocomposite. FESEM images portray the presence of thin layers of graphene sheets and Ag-doped La 2 (MoO 4) 3 on the sheets of reduced graphene oxide. Ground state absorption studies show that the reduction of graphene oxide causes a hypsochromic shift in the absorption maxima of the graphene layers. The photoluminescence of Ag- La 2 (MoO 4) 3 @RGO demonstrates the utmost emission in the UV range caused by the valence band and conduction band's direct transitions in the band gap region. Z-scan method using Nd: YAG laser exposes that both nanocomposite and specific counterparts hold reverse saturable absorption behaviour. The source of optical limiting action is attributed to the excited state absorption process, emerging from the influence of the plasmon resonance state of Ag nanoparticles. Strong nonlinear absorption and lower onset limiting threshold make the Ag-La 2 (MoO 4) 3 @RGO nanocomposite desirable material for laser safety devices. [Display omitted] • Graphene Oxide (GO) was synthesized by Modified Hummer's method after which GO was chemically reduced to Reduced graphene oxide (RGO) and a nanocomposite with Ag-doped La 2 (MoO 4) 3 was prepared by a simple and facile co-precipitation method. • Linear and non-linear optical properties of Ag-La 2 (MoO 4) 3 @RGO nanocomposites were studied. • Z-scan experiment was performed using Nd: YAG laser which exhibits both nanocomposite and individual counterpart possess reverse saturable absorption behaviour. • The Nonlinear absorption coefficient and optical limiting threshold of the RGO nanocomposite is in the order of 10−10 m/W and 1012 W/m2 respectively. [ABSTRACT FROM AUTHOR]

With the increasing processing power of micro-electronic components and increasing spatial limitations, ensuring sufficient heat dissipation has become a crucial task. This work presents a microscopic approach to increasing the surface area through periodic surface structures. Microstructures with a periodic distance of 8.5 µm are fabricated via Direct Laser Interference Patterning (DLIP) on stainless steel plates with a nanosecond-pulsed infrared laser and are characterized by their developed interfacial area ratio. The optimal structuring parameters for increasing the surface area were investigated, reaching peak-to-valley depths up to 12.8 µm and increasing surface area by up to 394%. Heat dissipation in a natural convection environment was estimated by measuring the output voltage of a Peltier element mounted between a hot plate and a textured sample. The resulting increase in output voltage compared to an unstructured sample was correlated to the structure depth and developed interfacial area ratio, finding a maximum increase of 51.4%. Moreover, it was shown that the output voltage correlated well with the structure depth and surface area.

Calcium electroporation (CaEP) is an innovative approach to treating cancer, involving the internalization of supraphysiological amounts of calcium through electroporation, which leads to cell death. CaEP enables the replacement of chemotherapeutics (e.g., bleomycin). Here, we present a standard microsecond (μsCaEP) and novel high-frequency nanosecond protocols for calcium electroporation (nsCaEP) for the elimination of carcinoma tumors in C57BL/6J mice. We show the efficacy of CaEP in eliminating tumors and increasing their survival rates in vivo. The antitumor immune response after the treatment was observed by investigating immune cell populations in tumors, spleens, lymph nodes, and blood, as well as assessing antitumor antibodies. CaEP treatment resulted in an increased percentage of CD4+ and CD8+ central memory T cells and decreased splenic myeloid-derived suppressor cells (MDSC). Moreover, increased levels of antitumor IgG antibodies after CaEP treatment were detected. The experimental results demonstrated that the administration of CaEP led to tumor growth delay, increased survival rates, and stimulated immune response, indicating a potential synergistic relationship between CaEP and immunotherapy.

Laser surface texture is very effective in antifriction systems, but its applications and research in dry friction are not enough. In this study, the groove texture was prepared on the surface of 0Cr17Ni7Al stainless steel, a common material of sliding bearing, by nanosecond and femtosecond laser, respectively. The tribological properties of the two kinds of laser groove textures with different collision frequencies were studied in depth. The results show that the friction coefficients of groove texture prepared by nanosecond and picosecond lasers are lower than that of the untextured surface. The antifriction characteristics of the laser texture are very good. The average friction coefficient of nanosecond texture at the rotation radius of 15 mm is Z = 0.7318. The best friction-reducing effect is achieved. In general, the friction coefficient of nanosecond texture is lower than that of picosecond texture. When the friction radius is 22.5 mm and the number of collisions is 24,000, the lowest picosecond texture wear rate is H = 3.342 × 10−4 mm3/N·mm. However, when the radius is 15 mm and the collision frequency is 36,000 times, the wear rate of nanosecond texture reaches the highest H = 13.680 × 10−4 mm3/N·mm. The wear rate of the untextured surface has been exceeded. It can be seen that not all rotation radius textures are more wear-resistant than untextured surfaces. In addition, nanosecond groove texture and picosecond groove texture seem to produce different tribological properties. It is found that, under the same friction experimental conditions, different collision frequencies will affect the friction and wear properties of nanosecond and picosecond groove-textured surfaces. [ABSTRACT FROM AUTHOR]

Ultrashort-pulse lasers allow to deposit extremely large peak intensities into a material, albeit with an exquisite precision. Thus, they have become a prevalent tool in many processes that require micro-precision material modification. One such applications is the micro-structuring of functional surfaces in Liquid Chromatography Mass Spectrometry instruments. Laser light can be tailored to induce permanent changes to the surface properties of materials not easily achieved by other means, for example to change the local chemistry, the local crystal structure and the local morphology. Such methods are expected to affect the behaviour of electrodes in a Liquid Chromatography Mass Spectrometry instrument. Structuring the incident laser light enables tailored laser-material interactions to be controlled with very high spatial resolutions, leading to extremely accurate control of the local surface properties relative to the bulk and other regions on the surfaces. [ABSTRACT FROM AUTHOR]

In this study, nanosecond-pulse lasing was achieved using a vertical-external-cavity surface-emitting laser (VECSEL) with only a single gain chip. A simple linear-cavity setup was used for the VECSEL, and pulsed lasing with a pulse width of ∼9 ns and a repetition frequency of ∼54 MHz was achieved. Dual-wavelength lasing at 974 and 978 nm was observed. The average output power during pulsed operation exceeded 100 mW. As the pumping power was increased, the laser output power could be switched off. However, stable dual-wavelength emission was maintained. The maximum output power under dual-wavelength operation could reach 455 mW. [ABSTRACT FROM AUTHOR]

This paper aims to study the mechanism of glass deep-hole micro-drilling by the Laser-Induced Plasma-Assisted Ablation (LIPAA) process. The Micro-drilling of glass was studied under various laser intensities. Nd:YAG nanosecond pulsed laser with 12 ns pulse duration was used as the laser light source. Copper was used as the metal target for the experiments. It is shown that laser glass micro-drilling is divided into two ablation stages. In the first stage, ablation is done by the brittle failure of glass caused by the collision of plasma plume with the glass surface. Exertion of mechanical pressure is also an important factor in the first few laser shots. Due to mechanical failure, glass microstructure changes in the focal spot. Second stage ablation is directly conducted by the thermal mechanism through absorption of laser by the glass. The hole produced on the glass by thermal mechanism is free of cracks. Cylindricity and roundness of the hole are very desirable. Laser intensity plays a vital role in material removal rate, hole depth and diameter. The process can be used for high-speed deep-hole micro-drilling of transparent materials to laser with good surface integrity and high-aspect ratio. [ABSTRACT FROM AUTHOR]

• Semiconductor laser processing with mid-infrared 2.8-μm and 2.5-ns pulses. • Multiphoton-initiated front, bulk, and rear surface processing of Si, InP, and GaAs. • Si volume processing through germanium for multilayered chips. • 3D pattern writing with positive refractive index variation of 0.5% The advent of more powerful mid-infrared nanosecond laser sources allows using them as attractive tools in material laser processing. For semiconductor bulk processing, laser intensities must remain modest to avoid detrimental nonlinear propagation and pre-focal plasma screening effects. Accordingly, nanosecond pulses are usually appropriate to locally initiate energy deposition by multiphoton absorption and subsequent modification, hardly achievable with ultrashort pulses. Employing a 2.8-μm 2.5-ns laser source, we explore the possibility to modify silicon and other semiconductors. With interactions initiated by three-photon absorption, we modify and determine the surface and bulk modification thresholds of Si, GaAs, and InP. For Si, compared to previous studies at telecom wavelengths, we report on a reduction of the energy threshold for volume modification with processing depth, and repeatable rear-surface modifications. Compared to Si, we find for GaAs and InP important fluctuations in the modification responses, which we attribute to an absorption mechanism initially triggered by a greater presence of defects. We also study germanium, as this narrower bandgap semiconductor very interesting for mid-infrared electro-optical applications is transparent at the newly introduced wavelength. Despite the ability to modify the surface, the bulk of Ge remains inaccessible in this two-photon regime, mainly attributed to beam aberrations and nonlinearities. Nonetheless, we demonstrate the ability to process Si chips integrating Ge layers. All these results showcase the potential of mid-infrared wavelengths to offer new degrees of flexibility for 3D laser processing technologies turned to silicon photonics and microelectronics packaging. [ABSTRACT FROM AUTHOR]

• This is the first report, to our knowledge, of a study on Mo 2 Ga 2 C DSF saturable absorber in Erbium doped fiber laser cavity. • The modulation depth of Mo 2 Ga 2 C DSF SA is 7.2 %. • The microsecond and nanosecond pulse has a pulse width of 7.02 µs–5.92 µs. Meanwhile, the repetition rate showed measurements between 64.6 to 64.6 kHz corresponding to the maximum pulse energy of 150.15 nJ. • Besides that, the dual wavelength nanosecond pulse began at the pump power of 95.22 mW with a pulse width of 273.7 ns corresponding to the repetition rate of 961.8 kHz. This paper elaborated the generation of microsecond and nanosecond pulse fiber laser using Mo 2 Ga 2 C coating onto DSF. The microsecond pulse commenced at the pump power of 39.826 mW and increased to 81.37 mW with a pulse width of 7.02 µs–5.92 µs. Meanwhile, the repetition rate showed measurements between 42.63 kHz to 64.6 kHz corresponding to the maximum pulse energy of 150.15 nJ. Besides that, the nanosecond pulse was generated with an additional length of 200 m for the SMF. The dual wavelength nanosecond pulse began at the pump power of 95.22 mW with a pulse width of 273.7 ns corresponding to the repetition rate of 961.8 kHz. Maximum pulse energy and maximum peak power were 8.75 nJ and 28.15 mW, respectively. The Mo 2 Ga 2 C coated DSF acted as the SA and was integrated into an erbium doped fiber laser cavity. The modulation depth of the Mo 2 Ga 2 C DSF SA was approximately 7.2 %. [ABSTRACT FROM AUTHOR]

• High throughput layer-by-layer laser milling. • Low surface roughness laser milling. • Laser milling of aluminum molds for LED diffusers. • Comparative study of ablation efficiency using ns, ps, and hybrid ns-ps pulses. • The highest values of laser milling efficiencies recorded in the literature. This paper reports a comparative study of ablation efficiency and quality using conventional nanosecond (ns), conventional picosecond (ps), and novel hybrid ns-ps irradiation modes. The aluminum alloy was machined using a laser with the traditional ns and ps pulses at various repetition rates. Also, the hybrid ns-ps irradiation regime was applied for the first time in laser milling. Laser fluence was optimized to ensure the efficient utilization of laser pulse energy for the maximal rate of material removal. For hybrid ns-ps, conventional ns, and conventional ps pulse processing regimes, direct comparisons of surface roughness of laser-milled cavities as well comparisons of ablation efficiencies with literature values were conducted. Experimental results coincided well with the theory of efficient ablation. The layer-by-layer efficient laser milling technique was applied for the fabrication of aluminum molds designed for LED diffusers. [ABSTRACT FROM AUTHOR]

In this work, a unified numerical model is used to determine the melting thresholds and to investigate the early stages of melting of several crystalline semiconductors (Si, Ge, GaAs, CdTe and InP) irradiated by nanosecond laser pulses. A molten fraction approach is used for continuous transition over the melting point. The results are compared with previously published theoretical and experimental data. A survey on the thermophysical and optical properties of the selected materials has been carried out to gather the most relevant data on temperature dependent properties for the solid and liquid states of these semiconductors where such data are available. A generalization of the obtained results is established that enables evaluation of the melting thresholds for different semiconductors based on their properties and irradiation conditions (laser wavelength, pulse duration).

The detailed study of the initial and collapse processes of the laser-induced cavitation requires nanosecond resolution (both nanoseconds exposure and nanoseconds interframe time) of the photography measurement system. The high-speed video cameras are difficult to achieve nanoseconds interval time. The framing and streak cameras are able to reach the nanosecond resolution, but their complex technology and expensive prices make them far from being commercially available. The present study builds a nanosecond resolution photography system based on PIV dual-head laser and conventional industrial camera. The exposure time of the photography system is controlled by the laser pulse width, which is 5 ns. The two heads of the PIV laser are operated independently thus the smallest time interval between two laser pulses can be set to less than 10 ns. A double-pulse per-exposure imaging technique is used to record the information from two laser pulses on single frame on a low-speed industrial camera. The nanosecond resolution photography system was applied to the laser-induced cavitation experiments to verify the reliability of the measurement results. The measurement of the shock wave velocity demonstrates the ability of the system to capture ultrafast phenomena, which reduces from 3611 m/s to approximately 1483 m/s within 400 ns. The experimental results also reveal the asymmetric evolution of laser-induced cavitation bubbles. The major axis of the ellipsoidal bubble has twice reversals along the laser propagation and perpendicular direction from the laser-induced breakdown to the first collapse.

In this work, a time-dependent and time-independent study on bleomycin-based high-frequency nsECT (3.5 kV/cm × 200 pulses) for the elimination of LLC1 tumours in C57BL/6J mice is performed. We show the efficiency of nsECT (200 ns and 700 ns delivered at 1 kHz and 1 MHz) for the elimination of tumours in mice and increase of their survival. The dynamics of the immunomodulatory effects were observed after electrochemotherapy by investigating immune cell populations and antitumour antibodies at different timepoints after the treatment. ECT treatment resulted in an increased percentage of CD4+ T, splenic memory B and tumour-associated dendritic cell subsets. Moreover, increased levels of antitumour IgG antibodies after ECT treatment were detected. Based on the time-dependent study results, nsECT treatment upregulated PD 1 expression on splenic CD4+ Tr1 cells, increased the expansion of splenic CD8+ T, CD4+CD8+ T, plasma cells and the proportion of tumour-associated pro inflammatory macrophages. The Lin− population of immune cells that was increased in the spleens and tumour after nsECT was identified. It was shown that nsECT prolonged survival of the treated mice and induced significant changes in the immune system, which shows a promising alliance of nanosecond electrochemotherapy and immunotherapy.

Objective: To examine the effectiveness of a recently developed nonthermal technology, nanosecond pulse-field ablation (nsPFA), for surgical ablation of the atria in a beating heart porcine model., Methods: Six pigs underwent sternotomy and ablation using an nsPFA parallel clamp. The ablation electrodes (53 mm long) were embedded in the jaws of the clamp. Nine lesions per pig were created in locations chosen to be representative of the Cox-maze procedure. Four lesions were intended to electrically isolate parts of the atrium: the right atrial appendage, left atrial appendage, right pulmonary veins, and left pulmonary veins. For these lesions, exit block testing was performed both after ablation and before euthanasia; the time between the 2 tests was 3.3 ± 0.5 hours (range, 2-4 hours). Using purse string sutures, 5 more lesions were created up to the superior vena cava, down to the inferior vena cava, across the right atrial free wall, and at 2 distinct locations on the left atrial free wall. The clamp delivered a train of nanosecond duration pulses, with a total duration of 2.5 seconds, independent of tissue thickness. The heart tissue was stained with 1% triphenyltetrazolium chloride after a dwelling period of 2 hours. Subsequently, each lesion was cross sectioned at 5-mm intervals to assess the ablation depth and transmurality. In some sections, transmurality could not be established on the basis of triphenyltetrazolium chloride staining alone; for these lesions, Gomori-trichrome stains were used, and the histologic sections were evaluated for transmurality., Results: The ablation time was 2.5 seconds per lesion, for a total of only 22.5 seconds ablation time to create 9 lesions. A total of 53 lesions were created, resulting in 388 separate histologic sections. Transmurality was established in 386 sections (99.5%). Mean tissue thickness was 3.1 ± 1.5 mm (range, 0.2-8.6 mm). Exit block was confirmed in 23 of the 24 lesions (96%) postablation and 23 of 24 (96%) before the animals were humanely killed. Over the course of the procedure, neither pulse-induced arrhythmias nor any other complications were noted., Conclusions: The novel nsPFA clamp device was effective in creating acute conduction block and transmural lesions in both the right and left atria in an acute porcine model. This nonthermal energy source has great potential to both shorten procedural time and enable effective ablation in the beating heart., Competing Interests: Conflict of Interest Statement Dr Zemlin holds stock in Pulse Biosciences, Inc, and receives research funding from Pulse Biosciences, Inc. Dr Damiano reported research funding from Pulse Biosciences, Inc; speaker and receives research funding from AtriCure, Inc; and speaker and consultant for Medtronic and Edwards Lifesciences. All other authors reported no conflicts of interest. The Journal policy requires editors and reviewers to disclose conflicts of interest and to decline handling or reviewing manuscripts for which they may have a conflict of interest. The editors and reviewers of this article have no conflicts of interest., (Copyright © 2024. Published by Elsevier Inc.)

Background: Nano-Pulse Stimulation (NPS) therapy applies electric pulses in the nanosecond domain to initiate regulated cell death in the treated tissues. This nonthermal therapy has been used to treat a wide range of murine tumors and has been shown to activate the immune system to inhibit the growth of rechallenge tumors, as well as untreated, abscopal tumors when accompanied by the injection of immune system stimulants into the treated tumors. Clinical trials have begun using NPS to treat basal cell carcinoma and hepatocellular carcinoma., Methods: Murine tumors can be easily imaged when the tumor cells are injected intradermally so that they grow within the mouse skin. Pulling the skin over a translucent light post shines light through the skin and makes it easy to treat the tumor and identify the treatment zone., Results: Original research using murine tumor models is described, including melanoma, squamous cell carcinoma, lung carcinoma, breast carcinoma, and pancreatic carcinoma. The energy required to ablate these tumors has been determined with pancreatic carcinoma and lung carcinoma exhibiting 90% ablation with 240 mJ/mm 3 , lung carcinoma and squamous cell carcinoma requiring 360 mJ/mm 3 , and melanoma requiring 480 mJ/mm 3 . NPS therapy initiated a variable immune response indicated by the rejection of injected rechallenge tumor cells with melanoma and hepatocellular carcinoma exhibiting the strongest response and lung carcinoma, the weakest response. Following the original research data, a review of human clinical trials using NPS therapy is presented., Conclusions: NPS therapy offers a nonthermal, drug-free approach for oncology, which is limited only by applying energy to the tumor. This new immunogenic modality is just beginning to be applied in the clinic. The 87% efficacy of the first large clinical trial conducted by several medical personnel is impressive and indicates that NPS is an effective new modality for cancer treatment., (Copyright 2024, Mary Ann Liebert, Inc., publishers.)

CFRP plates are important advanced material used in the aerospace field, high-quality and high-efficiency drilling is the main application processing demand of CFRP. In this paper, a 532 nm nanosecond fiber laser with adjustable pulse duration is used and the scanning path was planned as Z-direction up-bottom incremental cutting, and X-Y direction concentric circle cutting scanning mode to realize the CFRP plates hole drilling, and obtain high drilling performance. The mechanisms of material removal for CFRP plates hole drilling under 532 nm nanosecond laser is explored, and it is mainly attributed to thermal evaporation accompanied by certain heating carbonization. The results show that a narrow width of HAZ can be obtained with short pulse duration, the minimum value of HAZ width at hole entrance edge is 18.74 µm, and the matrix material damage near the HAZ becomes small. Reducing the pulse duration also helps to decrease the drilling taper (minimum taper value 0.046), the taper of the drilling hole is smaller than that of the drilling dicing. But the drilling efficiency is reduced due to the low pulse energy with short pulse duration. [ABSTRACT FROM AUTHOR]

The formation of a gradient of atomic oxygen is demonstrated by means of a nanosecond non-equilibrium plasma for a varying gap size plane-to-plane electrode. Using a flat high-voltage electrode in front of a rounded triangle a 2.9 to 5 cm gap is formed over a 9.8 cm span. ICCD imaging determined an adequate ground electrode shape and slope to create a gradient. The plasma is formed by three consecutive high voltage pulses of -30, -40 and -50 kV in 100 mbar of air. O-TALIF measurements confirm that atomic oxygen production changed with gap size within the same plasma. This setup will be used to test detonation initiation by Zel'dovich gradient mechanisms in stoichiometric H 2 :O 2 mixtures. Novelty and Significance: A novel configuration of a nanosecond non-equilibrium discharge was developed to create a controllable gradient of atomic oxygen. This was achieved by using varying gap plane-to-plane electrodes to generate an electric field of varying strength along the length of the gap. This setup will be tested in combustible mixtures to initiate a detonation wave using a gradient mechanism of Zel'dovich. [ABSTRACT FROM AUTHOR]

Laser surface texture is very effective in antifriction systems, but its applications and research in dry friction are not enough. In this study, the groove texture was prepared on the surface of 0Cr17Ni7Al stainless steel, a common material of sliding bearing, by nanosecond and femtosecond laser, respectively. The tribological properties of the two kinds of laser groove textures with different collision frequencies were studied in depth. The results show that the friction coefficients of groove texture prepared by nanosecond and picosecond lasers are lower than that of the untextured surface. The antifriction characteristics of the laser texture are very good. The average friction coefficient of nanosecond texture at the rotation radius of 15 mm is Z = 0.7318. The best friction-reducing effect is achieved. In general, the friction coefficient of nanosecond texture is lower than that of picosecond texture. When the friction radius is 22.5 mm and the number of collisions is 24,000, the lowest picosecond texture wear rate is H = 3.342 × 10−4 mm3/N·mm. However, when the radius is 15 mm and the collision frequency is 36,000 times, the wear rate of nanosecond texture reaches the highest H = 13.680 × 10−4 mm3/N·mm. The wear rate of the untextured surface has been exceeded. It can be seen that not all rotation radius textures are more wear-resistant than untextured surfaces. In addition, nanosecond groove texture and picosecond groove texture seem to produce different tribological properties. It is found that, under the same friction experimental conditions, different collision frequencies will affect the friction and wear properties of nanosecond and picosecond groove-textured surfaces.

We demonstrate a more than 50-fold enhancement in the upconversion of methane to higher order hydrocarbons by discharging a nanosecond-pulsed plasma across Au nanoparticles. Here, the enhancement occurs as a result of the local field enhancement provided by the nanoparticles. The transient nature of the pulsed plasma enables the structure of these delicate nanoparticles to be preserved during the plasma discharge by producing a low-temperature plasma. Plasma emission spectroscopy shows signatures of the C2 Swan bands with and without the presence of these nanoparticles. Mass spectrometry demonstrates that methane is converted into higher order hydrocarbons with different groups of peaks representing species with molecular masses of 35–45, 45–60, and 60–70 amu, corresponding to C3, C4, and C5 species, respectively, under plasma discharge conditions. Electrostatic simulations show that a 3–4× enhancement in the field is produced at the nanoparticle surfaces. The exponential relation between electric field strength and plasma formation gives rise to a 50× increase in highly reactive, plasma-initiated radical species that are responsible for driving the methane upconversion process. This upconversion is important for several applications including mitigation of greenhouse emissions and improving the combustion of natural gas. [ABSTRACT FROM AUTHOR]

An effective strategy to produce grooves on carbon steel substrates by nanosecond laser radiation is proposed. The aim is to increase the productivity of grooves creation. In this study, two different modes of laser treatment are compared. The first mode focuses on the evaporation of material, while the second focuses on the formation of melted material and its removal by the action of pressure vapors produced by evaporated material. Within some ranges of processing parameters, the shape of the groove can be linearly controlled. The dependence of the groove depth also has a logarithmic nature when the number of passes is increased. Using the liquid phase mode in some ranges of parameters can reduce the amount of evaporated material in comparison with standard techniques in which the material is removed in the form of gas, and fine dust is emitted.

Nanosecond pulsed electric fields, also known as Nano-Pulse Stimulation or NPS, can trigger regulated cell death to clear skin lesions that are cellular in nature. Before treating facial lesions, it is important to demonstrate the effects of these pulses on normal facial skin. Here we have applied a range of NPS energies to the epidermis and dermis of normal facial skin scheduled for excision to establish a safe dose range of energies prior to use in clinical applications. This was an open-label, non-randomized study under the direction of a single Principal Investigator. The time course of the treated tissue changes was determined by histological analysis. All energy settings generated a delayed epidermal loss followed by re-epithelialization by day 7 and a normal course of healing. One day after NPS treatment, the cellular membranes of the treated epidermis were intact, but their nuclei no longer stained with H&E, resulting in a hollow appearance that has been referred to as "ghost cells." Cellular structures in the dermis, such as sebaceous glands and melanocytes, exhibited regulated cell death observed by 1 day post treatment. Melanocytes recovered to their normal density within 7 days. The 60-day samples indicated that epidermis, hair follicles, and eccrine glands appeared normal. The selective effect of NPS treatment on cellular structures in the epidermal and dermal layers suggests that this non-thermal modality of energy delivery is ideal for treating cellular targets including benign and malignant skin lesions. NPS skin treatments provide a promising method for clearing skin lesions with a cellular basis. [ABSTRACT FROM AUTHOR]

• High-power cavity-dumped Tm laser, with high repetition frequency about 100 kHz is developed with a dual-end pumped configuration. • A plano-convex lens is used to compensate severe thermal lens inside the Tm:YAP crystal. • Maximum output power for the cavity-dumped Tm lasers, with a value of 10.07 W at 1.94 μm is obtained with pulse duration of 26.4 ns at 110 kHz. We demonstrate a high-repetition-frequency, cavity-dumped Tm:YAP slab laser, producing short nanosecond pulse at 1.94 μm. A thermal-lens-compensated cavity with a dual-end pumping configuration is developed for high-power operation. The achieved maximum Tm laser power is 10.7 W, with a pulse width of 26.4 ns at a frequency of 110 kHz, resulting in a peak power of 3.68 kW. To the best of our knowledge, this represents the highest output power for the cavity-dumped Tm laser. The results provide a robust scheme to develop high-power, high-repetition-frequency diode-pumped 2 μm lasers with a constant sub-50 ns pulse duration, opening avenues for versatile applications including medical treatment, material processing, and nonlinear frequency conversion towards the mid-infrared region. [ABSTRACT FROM AUTHOR]

Aims: Pulsed field ablation (PFA) is emerging as a non-thermal, tissue-specific technique for pulmonary vein isolation (PVI) in atrial fibrillation therapy. This pre-clinical study aims to investigate the feasibility and safety of PVI using a novel PFA system including a nanosecond-scale PFA generator, a novel lotos PFA catheter, and a customized 12 Fr steerable sheath., Methods and Results: A total of 11 Yorkshire swine were included in this study, with 4 in the acute cohort and 7 in the chronic cohort. Under general anaesthesia, transseptal puncture and pulmonary vein (PV) angiography was initially performed. The PFA catheter was navigated to position at the right and left PV antrum after the electroanatomic reconstruction of the left atrium. Biphasic PFA applications were performed on PVs in both the spindle-shaped and the lotos-shaped poses. Pulmonary vein isolation and PFA-associated safety were assessed 30 min after ablation in both cohorts and 30 days later in the chronic cohort. Detailed necropsy and histopathology were performed. Additional intracardiac echocardiography and coronary angiogram were evaluated for safety. All target PVs (n = 20) were successfully isolated on the first attempt. No spasm of coronary artery or microbubble was seen during the procedure. Eleven of 12 PVs (91.6%) remained in isolation at the 30-day invasive study. No evidence of PV stenosis was observed in any targets. However, transient diaphragm capture occurred in 17.6%. Histopathological examinations showed no evidence of collateral injury., Conclusion: This study provides scientific evidence demonstrating the safety and efficacy of the novel PFA catheter and system for single-shot PVI, which shows great potential., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.)

We present a linearly polarized narrow-linewidth nanosecond fiber amplifier with a repetition rate of 400 kHz, pulse width of 2.8 ns, and a peak-power of up to 75 kW. The pulsed source is realized by modulating a continuous-wave 1064 nm single frequency laser fiber from an arbitrary waveform generator using an elctro-optic intensity modulator. The amplifier is achieved by Master Oscillator Power-Amplifier(MOPA) which is constituted by two Pre amplifier stage and a final amplifier stage. Good beam quality is found with measured beam propagation factor of M2 = 1.29. [ABSTRACT FROM AUTHOR]

We fabricate Au microneedle structures by irradiating nanosecond optical vortex pulse, possessing orbital angular momentum (OAM), to Au thin film. Twisted microneedle associated with the handedness of optical vortex is formed. The partial liquid motion of the molten Au film and the OAM transfer effects play a role to establish a twisted Au microneedle. An Au microsphere on a twisted pillar is also achieved. Non-twisted structure is fabricated with picosecond optical vortex pulse irradiation due to unoptimized condition such as laser fluence, film thickness and unavoidable imperfections of the optical vortex. [ABSTRACT FROM AUTHOR]

Highlights • LIPSS formation with single NIR ns-pulses in SiO 2 was observed for the first time. • The LIPSS period can be adjusted by the laser parameters and deposited layers. • The LIPSS periods found were in a range between 400 nm and 600 nm. Abstract High-quality submicron pattern formation in dielectrics by lasers is challenging, in particular with regard to large areas. Self-assembly and self-organization mechanisms, which arise from the interaction of the laser photons with the material of the sample, can provide conditions for efficient micron patterning of large surface areas. This study demonstrates the formation of submicron ripples in fused silica (SiO 2) by nanosecond laser irradiation, which extends the category of lasers capable of the controllable manufacturing of laser-induced surface structures (LIPSS). A newly designed layer system was deposited on the surface of samples, comprising, on top of the dielectric substrate, an interlayer, an absorber, and a confinement layer. The samples were irradiated though the dielectric substrate with single nanosecond (λ = 1064) nm laser pulses. It was found that the period of the LIPSS can be tuned by changing the nanosecond laser energy, the confinement strength, and the laser pulse length from 5 ns to 25 ns. LIPSS with periods in the range of 400–600 nm, with a depth of up to 140 nm and with an orientation perpendicular to the polarization direction of the laser light, were found experimentally. The design of the sample finally enables an intra-pulse modification of the dielectric surface that provides temporal conditions near the dielectric substrate surface for surface plasmon polaritron (SPP) generation. The proposed mechanism of LIPSS formation thus comprises the ablation of the absorber layer and a plasma formation confined between the substrate surface and the confinement layer. This process causes a modification of the substrate surface. In consequence, temporary SPP generation occurs at the modified SiO 2 surface, resulting in a lateral intensity modulation of the nanosecond laser beam within the pulse duration. This lateral intensity modulation of the laser pulse causes localized variation of the ablation, which finally results in the LIPSS found. The experimentally observed dependencies of the LIPSS period on the pulse energy, the confinement layer thickness, and the pulse length can be explained with the proposed model. The findings of this work provide a method of enabling local adjustment of the LIPSS period, which can be used in applications such as writing hierarchical structures of variable sizes. [ABSTRACT FROM AUTHOR]

Highlights • A range of structures were generated on stainless steel using laser surface texturing. • The durability of sustaining dry under different conditions of water was tested. • The surfaces of dual scale topography sustained dry under water for longer time. • Hybrid surfaces were prepared using simple, repeatable and durable method. Abstract Stable superhydrophobic and superhydrophilic surfaces were created using laser surface micro/nano patterning. These were based on periodic 3D micro/nanostructures produced on 316L stainless steel over large areas using nanosecond and picosecond laser surface fabrication. The effects of laser processing parameters on controlling the micro-/nano-topographical characteristics of 24 different types of structures were presented. Surface roughness, surface chemical composition and wettability (via water contact angle) of these surfaces were characterised. Aging experiments were carried out for up to 8 months to analyse the durability of the prepared surfaces under three conditions of water (hot, normal and icy). Samples with superhydrophobic characteristics, processed with the ps or ns lasers in air, kept dry (water repellent) for over 8 months when tested in ice water (0 °C–4 °C), whilst those stored in hot water (80 °C) or room temperature water could only be kept dry for 3–14 weeks. Samples processed in water had shorter water repellent life and samples processed with the ns laser in air had the longest water repellent periods. The hybrid superhydrophobic and superhydrophobic surfaces had a stability life for water repellent and water spreading of over 6 months. [ABSTRACT FROM AUTHOR]