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The spectral and laser output characteristics of Cr:ZnSe single crystals optically polished at four different lengths of 2, 3, 5, and 10 mm combined with or without antireflection (AR) coatings were investigated under pulse and continuous wave (CW) laser diode excitation at the wavelength of ~1.7 μm. The absorption and fluorescence spectra of Cr2+ ions were measured at room temperature. Optimization of laser system efficiency was performed step-by-step in dependence on the active length of the crystal sample, output coupler reflectivity, the duration of the pump pulse, and the repetition rate. For a given 1 : 1 transferring optics, a 3-mm thick AR-coated Cr:ZnSe crystal was chosen as optimal in pulse mode of operation: The ~10% higher maximum slope efficiency of ~39% with respect to optical-to-optical power conversion was obtained with the 3-mm thick AR-coated sample compared to the uncoated one. The laser system was characterized by an optimal repetition rate of 10 Hz and a pump pulse duration of 20 ms selected for its best efficiency performance. In CW mode, better results were observed with a thicker sample (5 mm, AR-coated). Specifically, the output power of ~2.7 W at the wavelength of ~2.4 μm with a slope efficiency of ~24% was obtained. In this case, the M2 beam parameter was measured as low as ~1.1 ± 0.1. Using a 0.8 mm thick MgF2 birefringent filter plate, the laser oscillations were continuously tunable in the range of ~2.1–2.7 μm within narrow spectral linewidths (5–10 nm FWHM) and a Gaussian beam profile in both the pulse and CW regimes. [ABSTRACT FROM AUTHOR]

In this study, we analyzed the laser cutting characteristics of pulse transverse electrical discharge in gas at atmospheric pressure (TEA) CO2 and ultraviolet (UV) pulse laser processing in a multilayer display panels. First, the numerical calculation for was performed to confirm the thermal characteristics of each materials and optical field distribution at the interface of different material layers. Also, processing characteristics were experimentally confirmed by measuring cutting profile and adhesion characteristics of layer interface. Experimental results show that the characteristics of multi layers polymer cutting have different trend from those in a single‐layer because of the optical and thermal properties of each layer. In particular, the interface of layers had a substantial affect due to optical field distributions and thermal characteristic difference. Also, the optical absorbance of layers affect adhesion at the interface. The result suggests proper processing condition to enhance the laser ablation processing quality of multilayer display panel. In conclusion, understanding the characteristics of multilayer laser cutting processing is important for determining the optimal conditions for display panel micromachining and enhancing the quality of laser cutting for the cutting edge technology. [ABSTRACT FROM AUTHOR]

In this study, CZTS (Copper Zinc Tin Sulfide) thin films were fabricated using the pulse laser deposition (PLD) technique. Pellets formed under a pressure of 5 tons were ablated with a Nd:YAG laser at a pulse energy of 700 mJ. The resulting plasma plume was generated through a range of pulse counts--200, 250, 300, 350, and 400--at a consistent frequency of 6 Hz. The structural properties of the films were investigated via X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD analysis revealed a polycrystalline tetragonal structure of the CZTS thin films, with an increase in peak quantity correlating to higher pulse counts. Concurrently, variations in grain size, strain, dislocation density, and lattice constants (a,c) manifested an irregular pattern as a function of pulse count. AFM assessments--comprising parameters such as root-mean-square (RMS) roughness, average diameter, and arithmetic mean height--indicated a peak in surface roughness at the maximum pulse quantity of 400. Optical properties were characterized using a UV-Visible Spectrophotometer (2700) across a spectrum ranging from 300 to 1100 nm. An increment in absorbance was noted with the rise in pulse number, whereas the direct bandgap exhibited a decrease from 3.6 to 2.8 eV. The films demonstrated exceptional potential for sensor applications, evidenced by transmittance levels exceeding 90%. Optical constants, including refractive index and extinction coefficient, were derived from the spectral data. The comprehensive analysis suggests that by manipulating the pulse count during PLD, not only can the structural properties of CZTS thin films be tailored, but their optical attributes can be optimized, paving the way for advanced applications in photonic sensors and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

A passively mode-locked Er-doped fiber laser employing ethylene glycol as a saturable absorber (SA) has been proposed and experimentally validated. The ethylene glycol-SA is fabricated by filling the space between the end facets of two optical patch cords inserted into a cannula with ethylene glycol. Utilizing such an SA with a modulation depth of 9.6 %, stable mode-locking operation are manifested in the laser cavity, including the production of bright pulse and bright-dark pulse pair. The generated bright pulse has a center wavelength at 1562.28 nm, a 3 dB bandwidth of 0.21 nm, a repetition frequency of 20.24 MHz, and a signal-to-noise ratio (SNR) of 57 dB. Through precisely manipulating the polarization state and the pump power in the laser cavity, the bright-dark pulse pairs can be successfully attained at the same repetition frequency. This is the first demonstration of a passively mode-locked fiber laser utilizing ethylene glycol as the saturable absorber. Due to their superior optical absorption characteristics, low cost, simplicity in fabrication and non-volatile nature, ethylene glycol-SAs have enormous potential in the field of nonlinear optics and ultrafast photonics.

Samples with different surface microstructures and elemental composition were fabricated by pulsed lasers with different pulse duration, including the millisecond laser remelting (RE), the bioceramic coating (BC), and nanosecond laser processing (NL) samples. The morphologies, chemical elements, phases, and valences of these samples were analyzed and characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The contact angles of the samples were measured in air and under water. Their cell activity and behavior were analyzed by cell proliferation and cytoskeleton staining experiments. The results show that the hydrophilicity and aerophobicity increase after laser treatment, and the wetting behavior of underwater bubbles is strongly related to the wettability of the sample in the air. None of the samples examined in the experiment are cytotoxic. During the initial culture, the greater unevenness of the BC and NL sample surfaces hinders the initial expansion of the cells. In contrast, the cell spreading area of the ground (G) and the RE samples is larger. The inclined sidewall in the V-shaped structure weakens the energy barrier in the groove-ridge combination (NL sample), allowing cells that rarely adhere to the sidewall to adhere successfully. In addition, the orderly distribution of adhesion sites created by laser processing further promotes cell adhesion on the inclined sidewalls. When the cells have been cultured to Day 7, the NL sample forms a clear directional distribution of cells with its unique V-shaped structure mimicking the placoid scale on the shark skin surface. [ABSTRACT FROM AUTHOR]

When a missile-borne pulsed laser forward detection system flies at supersonic speed, the laser beam will be distorted by the uneven outflow field, resulting in a significant reduction in ranging accuracy. In this paper, the impact of high flight speed on a pulsed laser detection system is studied. First, a new ray tracing method with adaptive step size adjustment is proposed, which greatly improves the computational efficiency. Second, the aerodynamic environment of a munition flying at high speed is simulated by an intermittent transonic and supersonic wind tunnel to obtain the schlieren data of the flow field at various Mach numbers. The schlieren data present a shock wave structure similar to that of the simulation. In addition, the variation patterns of the pulsed laser echo waveform of the model under different aerodynamic conditions are studied to evaluate the detectability and operational stability of the laser detection system under static conditions. The test results match the simulation results well, and the two offer relatively consistent shock wave structures, which verifies the correctness and effectiveness of the flow field simulation model. The test echo waveforms are in good agreement with the simulated echo waveforms; the relative errors between the peak values of test and simulated echo waveforms at various Mach numbers do not exceed 20%, and the correlation coefficients between the test and simulated echo waveforms all exceed 0.7, indicating high correlations between the two. [ABSTRACT FROM AUTHOR]

As the fatigue strength of metallic components may be affected by residual stress variation at small length scales, an evaluation method for studying residual stress at sub-mm scale is needed. The sin2ψ method using X-ray diffraction (XRD) is a common method to measure residual stress. However, this method has a lower limit on length scale. In the present study, a method using at a 2D XRD detector with ω-oscillation is proposed, and the measured residual stress obtained by the 2D method is compared to results obtained from the sin2ψ method and the slitting method. The results show that the 2D method can evaluate residual stress in areas with a diameter of 0.2 mm or less in a stainless steel with average grain size of 7 μm. The 2D method was further applied to assess residual stress in the stainless steel after treatment by laser cavitation peening (LCP). The diameter of the laser spot used for LCP was about 0.5 mm, and the stainless steel was treated with evenly spaced laser spots at 4 pulses/mm2. The 2D method revealed fluctuations of LCP-induced residual stress at sub-mm scale that are consistent with fluctuations in the height of the peened surface.

Silver nanoparticles (NPs) were made using double-distilled deionized water (DDDW) and pulsing laser ablation in liquid (PLAL) with Q-switched technology (Nd:YAG) laser (energy: 80 mJ, number of pulses: 500) at various wavelengths (1064 nm and 532 nm). The surface plasmon extinction (SPE) peaks were used to measure the PLAL process's formation quality. The SPE spectra showed a single sharp peak at about 400 nm, suggesting that pure and spherical silver was produced. The formation of silver particles was verified by UV–vis spectrophotometer absorption results. According to the AFM findings, as the wavelength of the laser beam used for preparation increased, the average grain size of the particles decreased. Finally, SEM images pointing to the produced silver nanoparticles spherical in their shape, were shown. The elemental analysis and chemical characterization with energy-dispersive X-ray spectroscopy (EDX) were performed on the produced samples. This confirmed the high purity of the obtained samples and the existence of Ag NPs. [ABSTRACT FROM AUTHOR]

The objective of this article was to investigate the dynamic evolution behaviors of plasma expansion plumes by pulses laser irradiating centimeter-scale spherical space debris. A calculated model of centimeter-scale spherical space debris irradiated by pulses laser was firstly deduced based on FEM (finite element method)/COMSOL, and the action rules of plasma expansion plumes by pulses laser-generated irradiating the debris were simulated for different laser powers and action times. The results showed that the velocity of plasma expansion plumes was increased with the increase of laser powers and action times. Especially, when the laser power was 700 kW and the action time was close to 25 µs, the maximum velocity of plasma expansion plumes approached 1.91 km/s, and the diffusion radius of plasma expansion plumes was increased by about 2.5 mm. Further, the diffusion radius was about twice that of 400 kW when the action time reached about 48 µs. As a result, by simulating the transient flow process of nanosecond pulses laser irradiating small spherical space debris, the flow field evolution information and plasma plumes evolution characteristics of centimeter-scale space debris at nanosecond time resolution were revealed. [ABSTRACT FROM AUTHOR]

A multi-wavelength pulse is generated using chemical vapor deposition method (CVD) to fabricate the topological crystalline insulator (TCI) Pb1-XSnXTe as a saturated absorber (SA). Compared with other SA materials, Pb1-XSnXTe have advantages of narrow bandgap and high optical absorption in the near-infrared region. The laser produced a stable four-wavelength lasing configuration characterized by a wavelength spacing of approximately 2 nm, with pulse duration, repetition rate, and signal-to-noise ratio (SNR) of 0.899 to 0.854 µs, 1.08 to 1.15 MHz, and 31.5 dB, respectively. The results indicate that the Pb1-XSnXTe-SA is suitable for pulsed generation in the near-infrared region and its potential in various fields, including super-resolution imaging, high-density optical storage, and three-dimensional laser lithography.

Single-event transient (SET)-induced soft errors are becoming a more significant threat to the reliability of electronic systems in space, especially for advanced technologies. The SET pulse width, which is vulnerable to SET propagation, is a critical parameter for developing SET mitigation techniques. This paper investigates the pulse-broadening effect in the process of SET propagation in logic circuits and the SET-sensitive region distribution in the layout using the pulsed-laser mapping technique in logic circuits implemented with 28 nm Ultra-Thin Body and BOX (UTBB) FDSOI technology. The experiments were carried out at the Naval Research Laboratory (NRL) to measure the SET-induced errors and map the SET-sensitive region distribution at various clock frequencies and laser energy levels. The results illustrate that the number of errors increases with the clock frequency and energy for combinational logic circuits and that the flip-flop SEU rate is less sensitive to clock frequency. The SET pulse-broadening effect was also observed using SET mapping for an OR gate chain at different laser energy levels. In addition, the simulation results revealed the mechanism of the SET pulse-broadening effect in an OR gate chain. [ABSTRACT FROM AUTHOR]

A numerical study of a model photoconductor under pulsed and continuous-wave laser excitation is presented. From the solution of a system of partial differential equations related to the populations of the conduction and valence bands, we analyze the time behavior of the photoexcited concentrations of electrons and holes where the diffusion phenomena and the presence of electric field are neglected. Additionally, for the three-level model, the population of trap levels is also introduced and analyzed as a third variable. The dynamics of electrons, holes and traps levels concentrations are studied in the presence of different types of pulse and harmonic laser photoexcitations. We show that an improved physical insight is obtained through a systematic analysis of the influence of the main physical parameters, such as generation and recombination rates, between the available energy levels. [ABSTRACT FROM AUTHOR]

Aiming at the problem of optical parameter estimation for semitransparent media， an inversion model for optical parameters of semitransparent media exposed to pulse laser irradiation is established. The quantum particle swarm optimization (QPSO) algorithm is adopted to estimate the refractive index and absorption coefficient. The effects of measurement error and thermophysical parameters on the inversion results are analyzed. The relationship between the inversion accuracy and measurement error is revealed by sensitivity analysis. The calculation results show that the established inversion model and the QPSO algorithm can accurately estimate the refractive index and absorption coefficient. Even with measurement error of 10%， the retrieval results still have strong robustness and high accuracy. This study can provide technical reference for obtaining the physical parameters of semitransparent media. [ABSTRACT FROM AUTHOR]

SRAM with high density CMOS technology is extremely sensitive to single event latch�up, so it is necessary to adopt corresponding protection strategies in space applications. For CTOS with reduced radiation resistance, circuit level protection becomes an important part to improve system reliability. A series of single event latch�up effect tests were carried out on CY62167DV30LL SRAM of CYPRESS Company by using laser single event effect test device. Through the linear fitting of the experimental results, the holding voltage of the SRAM is 1�5�1�6 V, and the holding current is 9�9�11�2 mA. According to the holding current, holding voltage, working current and working voltage, judge whether circuit level protection can be adopted. Two circuit level protection methods of power supply current limiting and divider resistor were proposed, and the value range of power supply current limiting and divider resistor were calculated quantitatively. In the previous literature, resistor is only used as a means of current limiting after latch�up trigger, which can not prevent the device from latch�up. It is found that the divider resistor can also achieve the purpose of preventing the latch�up under certain conditions. The two protection methods were verified by pulse laser test.

• By utilizing the liquid phase exfoliation technique, NbSe 2 nanosheets was transformed into a nonlinear optical modulation device, marking its inaugural use in 2 µm solid-state pulse lasers for the first time. • In the current study, we studied the electronic structure and optical properties of NbSe 2 through density functional theory (DFT). • A standard nonlinear saturable absorption test was conducted on NbSe 2 , demonstrating its excellent nonlinear saturable absorption characteristics. • The results demonstrate the great potential of NbSe 2 as an ultrafast photonic device and provides a huge impetus for the miniaturization of solid-state pulse lasers. Two-dimensional (2D) NbSe 2 is a new material with a variety of excellent properties. In this article, 2D NbSe 2 nanosheets are prepared using liquid phase exfoliation (LPE) and spin coating methods. At the same time, the properties of NbSe 2 were calculated by using density functional theory (DFT), exploring the changes in the electronic band structure of NbSe 2 with the number of layers, and studying the optical properties of NbSe 2. The nonlinear optical properties caused by the Pauli blocking effect and the absorption spectra are studied through typical nonlinear testing techniques and an ultraviolet–visible-near-infrared (UV–VIS-IR) spectrophotometer. In addition, 2 µm solid-state pulse lasers have important applications in a variety of fields. For the first time, 2D NbSe 2 nanosheets are prepared as saturable absorbers (SA) and applied them to solid-state lasers as nonlinear optical modulation devices, successfully achieving the generation of ultra-short pulse lasers with a pulse duration of 445.4 ps in 2 µm band. Our research results prove that 2D NbSe 2 nanosheets is a promising nanomaterial, can be prepared into nonlinear optical modulation devices with excellent performance, and show great application potential as ultrafast photonic devices. It is beneficial to the miniaturization of solid-state pulse lasers in subsequent applications. [ABSTRACT FROM AUTHOR]

• Diode pumped Nd: KNaY (WO 4) 2 crystal has been used for the first time to obtain laser output operating at 1.07 µm. • A stable passively Q-switched Nd: KNaY (WO 4) 2 laser with pulse width of 6 ns had been successfully achieved. • The effect of Cr4+: YAG initial transmission on the output pulse of passively Q-switched was studied by simulation. To our knowledge, a compact diode-pumped Nd: KNaY (WO 4) 2 laser operating at 1.07 µm has been successfully achieved for the first time. The passively Q-switched Nd: KNaY (WO 4) 2 pulse laser with the narrowest pulse width of 6.23 ns and peak power of 1.34 kW was obtained by experiment, and its laser characteristics were studied in detail. The effect of Cr4+: YAG initial transmission for pulse width of Nd: KNaY (WO 4) 2 output laser was investigated by theoretical analysis and numerical simulation. Finally, it was found that the theoretical and experimental results are basically in agreement. [ABSTRACT FROM AUTHOR]

When a missile-borne pulsed laser forward detection system flies at supersonic speed, the laser beam will be distorted by the uneven outflow field, resulting in a significant reduction in ranging accuracy. In this paper, the impact of high flight speed on a pulsed laser detection system is studied. First, a new ray tracing method with adaptive step size adjustment is proposed, which greatly improves the computational efficiency. Second, the aerodynamic environment of a munition flying at high speed is simulated by an intermittent transonic and supersonic wind tunnel to obtain the schlieren data of the flow field at various Mach numbers. The schlieren data present a shock wave structure similar to that of the simulation. In addition, the variation patterns of the pulsed laser echo waveform of the model under different aerodynamic conditions are studied to evaluate the detectability and operational stability of the laser detection system under static conditions. The test results match the simulation results well, and the two offer relatively consistent shock wave structures, which verifies the correctness and effectiveness of the flow field simulation model. The test echo waveforms are in good agreement with the simulated echo waveforms; the relative errors between the peak values of test and simulated echo waveforms at various Mach numbers do not exceed 20%, and the correlation coefficients between the test and simulated echo waveforms all exceed 0.7, indicating high correlations between the two.

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Aiming at the problem that the current Quantum Random Number Generator (QRNG) cannot simultaneously meet the high-speed and real-time requirements of random number generation in quantum key distribution communication, this paper improves the QRNG scheme based on pulse laser as light source to extract phase information. The random phase information is converted into right intensity information by single-mode Michelson interferometer, and then converted into electrical signal by high-speed Photo Detector (PD). Finally, the real-time quantum random number generation rate of 1. 1 Gbt/s is obtained by using 16 bit Analog-to-Digital Converter (ADC) with 250 MHz sampling rate and 50% extraction rate. A high-speed, real-time and integrated QRNG equipment is realized. At the same time, the advantages of this scheme and continuous laser as light source on principle and system design are compared. QRNG based on pulsed laser light source has passed various tests of China Academy of Information and Communications. The random number output by the product in the process of stable operation can pass 15 test standards specified on the State Cryptography Administration randomness test document GB/T 329152016 and Na¬tional Institute of Standards and Technology (NIST) test standards. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the current Quantum Random Number Generator (QRNG) cannot simultaneously meet the high-speed and real-time requirements of random number generation in quantum key distribution communication, this paper improves the QRNG scheme based on pulse laser as light source to extract phase information. The random phase information is converted into light intensity information by single-mode Michelson interferometer, and then converted into electrical signal by high-speed Photo Detector (PD). Finally, the real-time quantum random number generation rate of 1.1 Gbit/s is obtained by using 16 bit Analog-to-Digital Converter (ADC) with 250 MHz sampling rate and 50% extraction rate. A high-speed, real-time and integrated QRNG equipment is realized. At the same time, the advantages of this scheme and continuous laser as light source in principle and system design are compared. QRNG based on pulsed laser light source has passed various tests of China Academy of Information and Communications. The random number output by the product in the process of stable operation can pass 15 test standards specified in the State Cryptography Administration randomness test document GB/T 32915-2016 and National Institute of Standards and Technology (NIST) test standards.

The pulsed laser has gradually become the standard method of studying the single-event effects of micro-nano devices, and it is a powerful supplement to heavy ion experiments on single-event effects. In particular, with the continuous improvement of the technological range and operating frequency of electronic devices, the femtosecond pulse laser has the potential for broad applications and practical value in the single-event effects testing and radiation hardness evaluations of devices. The single-event effects of single-photon and two-photon absorption were studied with a laser of 1064 nm and 1260 nm, and the influences of SPA (single-photon absorption) and TPA (two-photon absorption) on the single-event transient voltage under different pulse laser energies were analyzed. The test results of the TPA SEE (single-event effect) were basically consistent with those of the SPA SEE, and the trend of the change in the transient voltage pulse was consistent. These results lay a foundation for the application of the femtosecond pulse laser in the performance evaluation and screening of space electronic devices and the radiation hardness evaluation of satellite electronic systems. [ABSTRACT FROM AUTHOR]

In the process of wood surface processing, it is easy to cause safety accident. Therefore, it is very necessary to find a new and clean processing method instead. In this paper, the laser automatic processing method is used instead of manual work, exploring the ablation of milled wood surfaces with nanosecond pulse laser. Four commonly used kinds of wood were selected, and milled separately in three different directions. The generation mechanism of micro burrs was analyzed under different working conditions. Then, a laser ablation experimental platform was established, and used to ablate the milling-induced burrs on the four kinds of wood. The ablated surfaces were observed under a scanning electron microscope (SEM). Based on the observations, the interaction between laser and surface burrs was investigated, and laser ablation deburring was modelled on ABAQUS. On this basis, the authors discussed how laser ablation deburring is affected by multiple laser parameters. The results show that cross-grain milling leads to more burrs on wood surface than parallel-to-grain milling and against-grain milling; for nanosecond laser ablation of wood surface burrs, the ablation efficiency and ablated surface quality could be optimized, when the output power falls between 300 mJ and 400 mJ; when the other parameters of the laser remain unchanged, there exists an optimal power density that helps to remove the surface burrs, without greatly affecting the nearby areas. The research results shed important new light on the deburring of wood products with the aid of pulse laser. Finally, it is proved that the mode of laser machining instead of traditional manual operation is feasible.

The silver acetylene silver nitrate loading technology of the light initiated high explosive, as one of important means to simulate the structural response of powerful pulsed X-ray, adopts the pulse laser initiation. It has advantages of improvement of practical control, heterogenous loading realization and simultaneous loading timeliness. In this paper, the physical and mathematical models of hot spot initiation and photochemical initiation of energetic materials under the action of laser are firstly established, and then the laser initiation mechanism of the light initiated high explosive is specifically analyzed, and the laser initiation experiment is conducted based on the optical adsorption property of the light initiated high explosive. From this study, the laser initiation thresholds of 193 nm, 266 nm, 532 nm, 1064 nm wavelengths are given, and they are 5.07 mJ/mm2, 6.77 mJ/mm2, 7.21 mJ/mm2 and 10.61 mJ/mm2, respectively, and the complete detonation process is verified by detonation velocity. This work technically supports the study of pulse laser initiation process, mechanism and explosion loading rule as well as the loading technology of the light initiated high explosive to simulate the structural response of X ray. [ABSTRACT FROM AUTHOR]

In this study, silver nanoparticles (AgNPs) were synthesized concurrently by use of a green method and pulsed liquid laser fragmentation (PLFL). The AgNP's, which were generated in an extract solution of Spincia Olercea in order to regulate their size, were focused on the laser wavelength of 532 nm. The influence on the characteristics of manufactured NPs of liquid medium concentration and irradiation time were investigated. While the pattern of X-ray diffraction (XRD) verified AgNPs, the UV–VIS spectrophotometry indicated a large absorption peak at about 406 &458 nm attributable to the typical plasm surface resonance (SPR) peak of the AgNPs acquired. The SPR peak changed to a shorter wavelength by increasing the irradiation period and the concentration of spincia olercea extract. This movement shows the size of the NPs being reduced. The influence from transmission electron microscopy images of PLFL was clearly demonstrated on size reduction. The PLFL method decreased the size of the AgNPs produced to less than 10 nm, depending on the experimental conditions. Bacterial growth was also efficiently inhibited by AgNPs. When combined with a chemical reduction procedure, the PLFL approach has shown to be an effective tool for checking the volumes of NPs. [ABSTRACT FROM AUTHOR]

The purpose of the experiment was to study the influence of the laser beam in pulse mode on metallic foils in order to obtain a spot weld. The welding process was carried out using the overlap weld method, using spot welds in various quantities. The Nd - YAG BLS 720 pulsed laser was used to conduct the experiment. The impact of the number of spot welds on the value of force needed to break the sample was examined. A number of measurements were carried out to determine the best process parameters. Butt welding and overlap welding were also performed using a continuous weld consisting of spot welds. Weld strength tests were performed to select the most appropriate parameters for the process under consideration.

Surface finish is one of the most important quality characteristics of titanium implants in the medical field. In this paper, a laser-assisted thermochemical polishing system based on scanning galvanometer was designed and built for the ultrahigh-precision polishing of titanium. The influence of the laser processing parameters and initial surface roughness of the workpiece on the final polishing results were systematically studied, and the polishing mechanisms were discussed. The results show that the final polishing quality was closely related to the laser pulse energy, spot overlapping rate, scanning times, and properties of the material itself but not to the initial surface roughness of the workpiece. In addition, the laser destroyed the passivation layer on the surface of the workpiece, resulting in direct contact between the titanium and etching solution. On the other hand, it induced the generation of a thermo-electromotive force, which caused the electrochemical corrosion on the workpiece surface, accelerating the dissolution of peaks on the surface of the material. The workpiece surface finish was improved because of the difference between the material dissolution rates of the peaks and valleys. Finally, ultrahigh-precision polishing of a commercially pure titanium surface was achieved using the optimized process parameters. [ABSTRACT FROM AUTHOR]

• This is the first demonstration of a passively mode-locked fiber laser employing ethylene glycol as the saturable absorber. • By appropriately adjusting the polarization and pump power, both the bright pulse and bright-dark pulse pair can be successively achieved and switched. • Ethylene glycol-SAs can be utilized in ultrafast fiber lasers for obtaining the desired pulse type. A passively mode-locked Er-doped fiber laser employing ethylene glycol as a saturable absorber (SA) has been proposed and experimentally validated. The ethylene glycol-SA is fabricated by filling the space between the end facets of two optical patch cords inserted into a cannula with ethylene glycol. Utilizing such an SA with a modulation depth of 9.6 %, stable mode-locking operation are manifested in the laser cavity, including the production of bright pulse and bright-dark pulse pair. The generated bright pulse has a center wavelength at 1562.28 nm, a 3 dB bandwidth of 0.21 nm, a repetition frequency of 20.24 MHz, and a signal-to-noise ratio (SNR) of 57 dB. Through precisely manipulating the polarization state and the pump power in the laser cavity, the bright-dark pulse pairs can be successfully attained at the same repetition frequency. This is the first demonstration of a passively mode-locked fiber laser utilizing ethylene glycol as the saturable absorber. Due to their superior optical absorption characteristics, low cost, simplicity in fabrication and non-volatile nature, ethylene glycol-SAs have enormous potential in the field of nonlinear optics and ultrafast photonics. [ABSTRACT FROM AUTHOR]

The pulsed laser has gradually become the standard method of studying the single-event effects of micro-nano devices, and it is a powerful supplement to heavy ion experiments on single-event effects. In particular, with the continuous improvement of the technological range and operating frequency of electronic devices, the femtosecond pulse laser has the potential for broad applications and practical value in the single-event effects testing and radiation hardness evaluations of devices. The single-event effects of single-photon and two-photon absorption were studied with a laser of 1064 nm and 1260 nm, and the influences of SPA (single-photon absorption) and TPA (two-photon absorption) on the single-event transient voltage under different pulse laser energies were analyzed. The test results of the TPA SEE (single-event effect) were basically consistent with those of the SPA SEE, and the trend of the change in the transient voltage pulse was consistent. These results lay a foundation for the application of the femtosecond pulse laser in the performance evaluation and screening of space electronic devices and the radiation hardness evaluation of satellite electronic systems.

In the process of wood surface processing, it is easy to cause safety accident. Therefore, it is very necessary to find a new and clean processing method instead. In this paper, the laser automatic processing method is used instead of manual work, exploring the ablation of milled wood surfaces with nanosecond pulse laser. Four commonly used kinds of wood were selected, and milled separately in three different directions. The generation mechanism of micro burrs was analyzed under different working conditions. Then, a laser ablation experimental platform was established, and used to ablate the milling-induced burrs on the four kinds of wood. The ablated surfaces were observed under a scanning electron microscope (SEM). Based on the observations, the interaction between laser and surface burrs was investigated, and laser ablation deburring was modelled on ABAQUS. On this basis, the authors discussed how laser ablation deburring is affected by multiple laser parameters. The results show that cross-grain milling leads to more burrs on wood surface than parallel-to-grain milling and against-grain milling; for nanosecond laser ablation of wood surface burrs, the ablation efficiency and ablated surface quality could be optimized, when the output power falls between 300 mJ and 400 mJ; when the other parameters of the laser remain unchanged, there exists an optimal power density that helps to remove the surface burrs, without greatly affecting the nearby areas. The research results shed important new light on the deburring of wood products with the aid of pulse laser. Finally, it is proved that the mode of laser machining instead of traditional manual operation is feasible. [ABSTRACT FROM AUTHOR]

This study experimentally demonstrates a Q‐switched fibre laser using a new tungsten tri‐oxide (WO3)‐based saturable absorber (SA). Using the drop and casting approach, we managed to prepare a thin film that contained WO3 powders in polyvinyl alcohol. A small bit of the film was used to form an SA which was placed in a ytterbium‐doped fibre laser cavity to generate a Q‐switched laser. The laser, operating at 1063.78 nm, was realised at the threshold pump power of 85 mW with a repetition rate of 23.87 kHz and a pulse width of 5.56 μs. At the pump power of 147 mW, the laser produced the maximum pulse energy of 625 nJ, signal‐to‐noise ratio of 59 dB, the repetition rate of 39.79 kHz and pulse width of 2.37 μs. To the best of our knowledge, this is the first demonstration of using WO3 SA to generate the pulse laser in the 1 μm region. [ABSTRACT FROM AUTHOR]

• Investigated dependence of the impulse on beam profile for various metal targets. • The ablation impulse, laser energy, and beam profile were observed simultaneously. • Derived equation connecting the profile and impulse using a simple physical model. In many previous studies, laser ablation impulse was evaluated using fluence, which is obtained by dividing the beam energy by the beam projection area on the target. This method does not consider the difference in the spatial profile of the beam energy. However, in certain applications, the effect of the profile should be evaluated for a more precise estimation of the impulse. In this study, the dependence of the ablation impulse of a nanosecond pulse laser on the beam profile was investigated. Pure aluminum, extra-super duralumin, and oxygen-free copper were used as the ablation target materials. The ablation impulse, laser energy, and beam profile were simultaneously observed. A dependence of the impulse on the beam profile was observed for all the target materials. A novel equation containing two tuning parameters that connect the profile and impulse was derived using a simple physical model. By fitting these parameters, the parameters with which the impulse could be predicted from the beam profile with sub- μ N · s precision was obtained for all the target materials. This work not only establishes a method for predicting the ablation impulse from a given profile, but also proposes parameters that are independent of the profile's effect. These parameters can be used to quantitatively evaluate impulse generation. [ABSTRACT FROM AUTHOR]

In this paper, a neodymium-doped fiber laser (NDFL) was integrated with Ti 3 C 2 T x -PVA SA to generate Q-switched operations, pertaining mainly for material processing, biomedical research, and optical communications. The Ti 3 C 2 T x -PVA SA was fabricated by using a solution casting technique, left to dry in the petri dish for 48 h and then secured inside the cavity by fitting it in between two fiber ferules. The NDFL operated at the center wavelength of 1088 nm with maximum repetition rate of 50 kHz. The attained pulse energy and peak power were 5.77 nJ and 3.17 mW, respectively. [ABSTRACT FROM AUTHOR]

In the present work, silver nanoparticle was synthesis by pulse laser ablation by using (Q-switched Nd:YAG) pulse duration10ns and (E=80mJ, λ=532nm) of silver metal target in deionize-water and ethanol. The results of XRD explain that not found any impurity in diffraction peaks in the pattern and Ag nanoparticles have high quality from of crystalline, which evidences the presence of silver particles with FCC structure. The optical properties were studied with Ultraviolet- Visible (UV-Vis) spectrophotometer which showed blue-shaft with pulse number, and atomic force microscope (AFM) indicates the size in nanometer (nm) range abut(40-80)nm.

Copyright of Iraqi Journal of Laser is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • RF sputter deposited thin films of TiO 2 , Ta 2 O 5 , HfO 2 and Gd 2 O 3 have been subjected to laser irradiation. • Samples were irradiated by varying laser fluence or number of pulse shots across their damage threshold. • XAFS and XANES measurements have been carried out on the irradiated spots of the samples. • The effect on the local structure in the sample during the onset of laser damage has been studied thoroughly. • Samples have also been characterized by optical microscopic imaging, GIXRD and GIXR measurements. Abstract Study of laser induced damage mechanism and effort to increase the damage threshold of oxide thin films is of immense technological importance because as improved laser-damage resistant optical materials and better fabrication technologies are developed, laser designers can increase the system operating energies and powers to the limits of these new materials. Although, many efforts have been made to investigate how stoichiometry or long range order structure plays a role in describing the laser damage process, to the best of our knowledge, efforts to understand the local structural changes in the materials due to laser irradiation around the damage threshold has not been made so far. In this communication, a set of RF sputter deposited dielectric refractory oxide thin film samples have been subjected to laser irradiation across their damage threshold. In case of TiO 2 , Ta 2 O 5 , and HfO 2 thin films, the samples were irradiated with optimized laser fluence and different locations on the samples were irradiated with varying number of pulse shots, while in case of Gd 2 O 3 films, different locations of the samples were irradiated with fixed number of pulse shots and with varying laser fluence. The irradiated samples have subsequently been subjected to X-ray absorption spectroscopy (XAS) studies to find out change in the local structure of the samples under laser irradiation. Apart from XAS measurements, various other characterization techniques such as optical microscopic imaging, grazing incidence X-ray reflectivity and grazing incidence X-ray diffraction have also been employed to study the laser irradiated zones. The results indicate interesting local structural evolution in oxide thin films with the onset of laser induced damage which gives novel insight about the laser damage mechanism. [ABSTRACT FROM AUTHOR]

• All-fiber laser configurations for Q-switching operation at 1.55- and 2-µm regions. • A 10 cm long Chromium-doped fiber (CrDF) as passive fiber saturable absorber. • The CrDF was fabricated through a MCVD in conjunction with solution doping method. • Signal-to-noise ratio of the generated pulses was about 71 dB. We demonstrate a Q-switching operation laser at 1.55- and 2-µm region using a homemade 10 cm long of Chromium-doped fiber (CrDF) as a passive saturable absorber (SA). Erbium-doped fiber (EDF) and Thulium-doped fiber (TDF) as a gain medium cooperate in the all-fiber ring cavity configuration. CrDF was fabricated by Modified Chemical Vapour Deposition (MCVD) technique in conjunction with conventional solution doping (SD) method. The CrDF has a saturable absorption of 9% at 1.55-µm region with a saturation intensity of 22 MW/cm2. Therefore, a stable pulse train obtainable within 75–173 mW, with a repetition rate increases from 68.12 kHz to 115.9 kHz. At the maximum pump level, a shorter pulse width, maximum output power, and maximum pulse energy are 3.85 µs, 10.86 mW, and 94.1 nJ, respectively. In TDF laser cavity, the laser pulsing generates from 363 mW to 528 mW, where the repetition rate increases from 13.02 kHz to 27.62 kHz. At maximum pump power, a shorter pulse width, maximum output power, and pulse energy are obtained with 4.48 µs, 6.36 mW, and 230.27 nJ, respectively. Both pulse trains at 1.55- and 2-µm region are stable with a signal-to-noise ratio (SNR) of 71 dB and 44 dB, respectively. These findings are important to the discovery of robust passive saturable absorber development in a form of fiber which has a similar melting point to the rest of the silica fiber in the proposed cavities. Thus, it will be a kick-started to alternative form of passive SAs in developing a future high-power fiber lasers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Kufa - Physics is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Laser rock breaking is a novel rock breaking technology to raise the rock breaking efficiency in deep and ultra-deep strata. Continuous and pulse lasers are two types of laser that are usually used in laser rock breaking research at present. However, the present studies' main focus is on the breaking mechanism and character optimization of continuous laser. Studies to pulse laser and the differences between the two types of laser are rarely reported. The pulse and continuous laser with 800 W power were used in the laser rock breaking experiment, and the morphology of ablation pits was measured and compared. Then, a FEM simulation model was established by the results of the experiment. The distribution condition and the evolution process of temperature, ablation pit, yield condition, and equivalent strain at test points generated by two types of laser were measured and compared. The experiment results show a thick enamel layer covering the ablation pit generated by the continuous laser, which referring a higher ablation ability but with a shallower ablation pit in measurement. And the simulation results not only represent the higher ablation ability of continuous laser at the end of simulation but also show the circular heating–cooling process, stepping expansion process of ablation pit, faster ablation pit generation speed (0.03 s earlier), higher yield volume, and higher equivalent plastic strain (about three times higher) in radiated part with a pulse laser. Referring that it has higher ablation ability in short radiation time, stronger thermal stress effects on the radiated part, and less molten materials generated in the laser rock breaking process than continuous laser. This research can offer some references to the laser type selection in laser rock breaking and explain the rock breaking theory more comprehensively. • A comparative laser rock breaking experiment were made and analyzed. • Various physical parameters are compared based on simulation model. • The advantages of pulse laser used in laser rock breaking process are discussed based on the results and formers' works. [ABSTRACT FROM AUTHOR]

Laser annealing of polyimide enhances the characteristics such as actuation and substrate-to-film adhesion of the NiTi shape memory alloy (SMA) bimorph. This work investigated the laser annealing of Kapton polyimide with 355 nm Nd: YAG laser for varying fluence and % line overlap (% LO). The laser annealing has enhanced the crystallinity of the polyimide surface below the laser fluence of 1630 mJ/cm2. Furthermore, annealing at 500 mJ/cm2 fluence at 90% LO and 1630 mJ/cm2 at 50% LO and 70% LO yielded low contact angles of 58.1° ± 3.6°, 42.7° ± 1.5°, and 57.5° ± 2.1°, respectively. The deposited film adhesion has significantly improved for annealing at 1630 mJ/cm2 at 70% LO. The bimorph fabricated on the mentioned substrates has produced higher tip displacement than the pristine substrate in the electrical actuation study. The maximum increment in tip displacement of the NiTi SMA bimorph was 1.5 mm in samples with annealed substrate compared to the as-fabricated bimorph. Moreover, the laser-annealed bimorph has shown the capability of enhanced tip displacement even with a loading of 45 mg. [Display omitted] • Enhanced the surface capability of polyimide towards SMA bimorph for better film deposition and actuation characteristics. • Laser annealing reduces contact angle of polyimide from 82° to 42.7° for laser fluence of 1630 mJ/cm2 at 50% line overlap. • Laser fluence of 1630 mJ/cm2 at 70% line overlap has improved the deposited NiTi film adhesion. • Tip displacement of the bimorph with laser annealing increased by 1.5 mm without external load and 1 mm with external load. [ABSTRACT FROM AUTHOR]

The most popular surface modification technology used to enhance the mechanical properties of metallic materials is shot peening. Shot peening improves fatigue life and strength by introducing local plastic deformation pits. However, the pits increase surface roughness, which is a disadvantage for fatigue properties. Recently, cavitation peening, in which cavitation bubble collapse impacts are used, has been developed as an advanced surface modification technology. The advantage of cavitation peening is the lesser increase in surface roughness compared with shot peening, as no solid collisions occur in cavitation peening. In conventional cavitation peening, cavitation is generated by injecting a high-speed water jet into water. However, cavitation peening is different from water jet peening, in which water column impacts are used. In the present review, to avoid confusing cavitation peening and water jet peening, fundamentals and mechanisms of cavitation peening are described in comparison to water jet peening, and the effects and applications of cavitation peening are reviewed compared with the other peening methods.

Light-matter interactions are greatly enhanced and spatially well-confined in plasmonic nanostructures in the spectral resonance range. In colloidal plasmonic nanoparticle (NP), this effect is manifested by the strong absorption caused by the collective oscillation of conduction electrons in NPs, known as the localized surface plasmon resonance (LSPR). The strong spectral resonance due to LSPR also contributes to the large enhancement in optical nonlinearity, such as nonlinear absorption and optical Kerr effect, and the ultrafast transient photo-bleaching in those materials making them ideal platforms for exploring optical switching behavior that is needed in all optical devices. Here, we review the recent advances in the use of colloidal processed noble metal, metalloid, chalcogenide and oxide plasmonic NPs for ultrafast optical switches to drive pulse laser generation in both solid state and fiber lasers. The broadband and ultrafast response of these plasmonic NPs offers a significant advantage in devices performance and allows the pulse generation from near infrared (NIR) to middle infrared (MIR) spectral range with pulse duration down to 100-femtosecond level. Compared with commercial products and other optical switches based on 2D materials, these plasmonic NPs are expected to provide a competitive and cost-efficient material solution to compact ultrafast pulse lasers and relevant devices.