High-power Nanosecond Research Articles

High average power nanosecond pulsed single longitudinal mode diamond Raman laser in the 1.6 µm waveband

High average power nanosecond pulsed single longitudinal mode diamond Raman laser in the 1.6 µm waveband

Laser hardening of aerospace structural materials

The work is devoted to the study of laser shock treatment of structural materials used in aviation and space technology with powerful nanosecond pulses in order to reduce surface damage, as well as resistance to crack growth. The hardening effect is achieved due to the mechanical deformation produced by the shock wave from the laser pulse due to the rapidly expanding plasma in the area of the irradiation spot. In this work, laser parameters for processing structural materials are calculated to ensure the required laser radiation power density. The results of laser processing with high-power nanosecond pulses of materials such as oxygen-free copper, aluminum alloy and germanium at various energy densities, with and without a protective coating and a water layer are shown.

High average power and high repetition rate eye-safe Raman laser driven by a two-crystal Nd:YVO4 laser.

We report on a high average power and high repetition rate nanosecond pulsed eye-safe KGW Raman laser intracavity driven by an acousto-optic Q-switched 1342 nm two-crystal Nd:YVO4 laser. Taking advantages of the carefully selected two-composite-laser-crystal configuration, the thoroughly optimized gate-open time of acousto-optic modulator and the ingeniously designed U-shaped resonator, substantial power and efficiency enhancements as well as superior mode matching have been enabled. Under the injected pump power of 64.5 W, the average output powers of the first-Stokes fields at 1496 and 1527 nm can be up to 8.1 and 9.5 W with 25 kHz repetition rate and 3.2 µs gate-open time, respectively, corresponding to the optical power conversion efficiencies of 12.6% and 14.7%. Meantime, the resultant pulse widths are determined to be 4.6 and 6.3 ns with the peak powers of approximately 70 and 60 kW, respectively. The beam quality can be maintained with M2 < 1.5 across the entire output power range.

On the Dendrite-Suppressing Effect of Laser-Processed Polylactic Acid-Derived Carbon Coated Zinc Anode in Aqueous Zinc Ion Batteries.

A major bottleneck limiting the commercialization of aqueous zinc ion batteries (AZIBs) is dendrite formation on the zinc (Zn) anode during the plating/stripping process, which leads to rapid deterioration in performance and, consequently to the device failure. In this regard, researchers are trying to design more stable anodes toward suppressing dendrite formation. One possible solution to tackle this problem and to extend the cycling life of AZIBs is to modify the zinc anode surface by coating carbonaceous materials, enabling more controlled charge flux and uniform ion distribution. This work reports sustainable and bio-derived polylactic acid (PLA) as a coating layer on the zinc anode. Carbonizing this polymer under ambient conditions using a high-power nanosecond laser forms a carbon-coated zinc foil, which was directly utilized as the anode in aqueous zinc ion batteries. The fabricated laser-processed PLA-derived carbon-coated zinc anode demonstrated an extended cycling life of almost 1600 hours, significantly outperforming the bare zinc anode. A full aqueous zinc ion battery assembled from as-modified anode and as-prepared V2O5 nanofibers as cathode was able to deliver a specific capacity of 238 mAh g-1 at 1.0 A g-1 with a capacity retention of 70 % after 1000 cycles.

High-power and narrow-linewidth nanosecond pulsed intracavity crystalline Raman laser operating at 1.7 µm

We report on a high-power and narrow-linewidth nanosecond pulsed intracavity crystalline Raman laser at 1.7 µm. Driven by an acousto-optically Q-switched 1314 nm two-crystal Nd:YLF laser, the highly efficient cascaded YVO4 Raman laser at 1715nm was obtained within the well-designed L-shaped resonator. Thanks to the absence of spatial hole burning in the stimulated Raman scattering process, significant spectral purification of second-Stokes radiation was observed by incorporating a fused silica etalon in the high-Q fundamental cavity. Under the repetition rate of 4 kHz, the highest average output power for single longitudinal mode operation was up to 2.2 W with the aid of precision vibration isolation and precision temperature controlling, corresponding to the pulse duration of ∼2.8 ns and the spectral linewidth of ∼330 MHz. Further increasing the launched pump power, the second-Stokes laser tended toward be always multimode, and the maximum average output power amounted to 4.8 W with the peak power of ∼0.8 MW and the spectral linewidth of ∼0.08 nm. The second-Stokes emission was near diffraction limited with M2 &lt; 1.4 across the whole pump power range.

High power nanosecond optical vortex laser oscillation in mode-selection slab resonator

High power nanosecond optical vortex laser oscillation in mode-selection slab resonator

New advance in high-reliability high-power nanosecond green laser developed domestically

New advance in high-reliability high-power nanosecond green laser developed domestically

Spectral behavior in ZnGeP2 and CdSiP2-based high-power nanosecond pulsed mid-IR parametric sources

Spectral behavior in ZnGeP₂ and CdSiP₂-based high-power nanosecond pulsed mid-IR parametric sources

Creation of High-Power Technological Nanosecond Frequency-Pulse Solid-State Lasers: Problems and Solutions

A review analysis of the problematic aspects of creating high-power nanosecond frequency-pulse solid-state lasers for use in various technological fields, including the electronics industry, has been carried out. Considered installations with various pumping methods (lamp and diode) in the frequency (about 100 Hz) of generation in the micron region of the infrared range. The possibilities of increasing the energy potential of influencing pulses in master oscillator-amplifier circuits, including two-pass amplification, are analyzed. Discussed possibilities and prospects for the use of lasers with active elements (AEs) on glass, as well as the synthesis of large-sized garnet single crystals with an admixture of rare earth elements and opticalceramics for the production of AEs.

Creation of High-Power Technological Nanosecond Frequency-Pulse Solid-State Lasers: Problems and Solutions

Creation of High-Power Technological Nanosecond Frequency-Pulse Solid-State Lasers: Problems and Solutions

Experimental investigation of high-power broadband all-fiber nanosecond superfluorescent source

In this work, we demonstrate a broadband nanosecond superfluorescent fiber source (ns-SFS) with an average power of several hundred watts and an adjustable repetition frequency of 25 kHz–100 kHz. To figure out a suitable active fiber length for ns-SFS seed, the impact of active fiber length on the output spectrum of SFS is investigated theoretically and experimentally. The results indicate an evident redshift in the central wavelength of output spectrum with increasing fiber length. By scaling the power of the ns-SFS seed employing three amplifier stages, the maximum average power and pulse energy are obtained with a value of 463 W, 17.6 mJ, respectively. To the best of our knowledge, this work is the first demonstration of a broadband ns-SFS amplifier with output power exceeding hundred watt and pulse energy exceeding 10 mJ.

A Generator of Nanosecond High-Voltage Pulses Based on Shock-Ionized Dynistors

—A generator of high-power nanosecond pulses consisting of four stages that are switched on in a relay-race mode is described. Each stage contains a storage capacitor with an operating voltage of 8 kV and an assembly of series-connected shock-ionized dynistors. The possibility of switching current pulses with an amplitude of 800 А to a load of 30 Ω a rise time of 4 ns, and a repetition rate of 100 Hz is demonstrated. The prospects for increasing the output voltage and the output energy of the generator are determined.

Technology of experiments on non-thermal effects of powerful lectromagnetic pulses on natural and artificial environments

The features of the technology of experiments on the non-thermal effects of high-power nanosecond pulses are considered using the example of a setup used to modify biological media and other objects with heterogeneous electrophysical characteristics. An experimental setup has been created to study the non-thermal effects of high-power pulses on samples of various materials, which generates pulses with a repetition frequency of up to 500 Hz, amplitude up to 60 kV and duration 5 ns. Simulation of transient processes in the equivalent electrical circuit of the load was carried out, and a biological one was used as a load material placed in a microplate.

Mutual influence of intermodal and fundamental four-wave mixing of 1.0 µm and 1.5 µm nanosecond pulses in a dual-wavelength fiber laser.

We introduce the experimental and theoretical investigation of the mutual influence of two four-wave mixing (FWM) processes during the propagation of high-power nanosecond pulses at 1030 nm and 1562 nm wavelengths in the few-mode optical fiber. Both fundamental mode FWM (FM FWM) of laser pulses at these wavelengths, and intermodal FWM (IM FWM) of 1030 nm pulses, have common anti-Stokes components at 1003 nm wavelength. This leads to the mutual influence of FWM effects. As a result, the decrease of optical power of the fundamental mode is observed at both 1030 nm and 1562 nm wavelengths. The method for the suppression of such an adverse effect is proposed. It is based on the attenuation of the 1030 nm higher LP11 mode at the few-mode optical fiber input.

NONLINEAR PHENOMENA DURING THE PROPAGATION OF POWERFUL NANOSECOND ELECTROMAGNETIC PULSES IN A LARGE-SCALE STRIPE LINES WITH A GAS AT REDUCED PRESSURE

Experiments of propagation of the high-power high-voltage nanosecond and subnanosecond pulses in large-scale transmitting lines in various gases make it possible to solve a wide range of fundamental and applied problems, from simulating the propagation of electromagnetic pulses (EMP) through the atmosphere to estimating the electrical strength of elements of pulsed high-voltage gas-filled systems. At the IAP RAS, experiments with stripe lines up to 5 m in length are performed in Krot and Sprite devices. During the propagation of EMP with an electric field strength up to 100 kV/m in a low pressure gas, the effects are observed such as the formation of non-uniform and essentially non-stationary glow, nonlinear absorption and dispersion transformation of the shape of high-power pulses, due to gas ionization in the EMP field.

Improved Marx Pulse Generator With Auxiliary Trigger Topology (2022)

Marx multi-stage circuits based on avalanche transistors are widely used in high-power nanosecond pulse applications. In response to the low reliability of the conventional Marx circuit, this paper analyzed the corresponding failure mechanism and discovered that the conduction modes were the main cause of failure. Based on this, a new topology is designed, by changing the conduction mode from "overvoltage switching-on" to "triggering switching-on". The simulation and measurement results show that the new structure has the advantages of high efficiency, stable operation, low output delay and short output pulse front. Meanwhile, to further improve the output efficiency,= a multiplexed stacking solution is designed based on the new structure, and the simulation results show that the output efficiency is up to 95%. The research in this paper can provide solutions for accurate and reliable synchronous triggering of key units such as gas switches in pulsed power systems, and also provide references for the design of high-efficiency nanosecond pulse generators.

Effect of double laser beam surface treatment on the surface morphological characteristics of Ti6Al4V at different heat source incidence angles

With the development of the high-end equipment manufacturing industry, the requirements for the surface performance of critical components are likewise increasing. To control the heat and mass transfer in the laser surface treatment process more efficiently and flexibly, the multiangle double laser surface treatment technology shows unique advantages. This study is focused on the experimental study of the laser surface treatment process for Ti6Al4V material. By changing the laser power and the incidence angle of the laser beam, the effects of single-laser beam surface treatment (SLST) and dual-laser beam surface treatment (DLST) on the surface morphology of the alloy were studied. The effects of laser treatment on the surface morphology, element distribution, roughness, surface chemical state, and surface structure of the alloy were emphatically analyzed. The mechanism of SLST and DLST at different incident angles of heat source and the effect of DLST on the formation of an oxide layer on the surface of the alloy were compared and analyzed. The results show that when the average power of the high-power nanosecond pulse width laser in DLST is 100 W and the incident angle is 135°, the surface oxygen content reaches the lowest, as low as 8.31%. The secondary effect of the laser makes the alloy surface remelt again, and then the best roughness after laser processing is obtained, with a roughness value of 2.801 μm. Finally, we obtain the optimal process for laser surface treatment and conclude that DLST can significantly optimize the surface state after a high-energy laser beam action.

Velocity Analysis of Supersonic Jet Flow in Double-Cone Ignition Scheme

Abstract In the double-cone ignition schemes (DCIS), the deuterium-tritium target shell is ablated and compressed by a high-power nanosecond laser in u-cones to generate plasmas. Under the actions of spherical symmetric compression and acceleration along the Au cone, they will be ejected out of the cone mouth and collide with each other. The plasmas witness conversion from kinetic energy to internal energy at the vertex of the geometric center of two Au cones that are symmetric to each other, because of which, fusion high-density plasmas are preheated. This key physical process has undergone experimental verification on the Shenguang-II upgraded facility of China. Apparently, the improvement and optimization of the velocity of plasmas in hypersonic jet flow at the cone mouth are crucial for the success of DCIS. In the DCI-R7 experiment for the Shenguang-II upgraded facility, a velocity yield of approximately 130-260 km/s was achieved for the plasmas at the cone mouth, with a result of nearly 300 km/s based on numerical simulation. In this paper, theoretical analysis is performed as regards the process, in which target shells are ablated and compressed by laser to generate high-velocity plasmas ejected through jet flow. Based on this analysis, the formula for the velocity of plasmas in supersonic jet flow at the cone mouth is proposed. This study also provides measures that are more effective for improving the kinetic energy of plasmas and optimizing energy conversion efficiency, which can serve as theoretical references for the adjustment and optimization of processes in subsequent experiments.

Nanosecond Laser Annealing of NMC 811 Cathodes for Enhanced Performance

Improved performance of lithium-ion batteries (LIBs) plays a critical role in the future of next- generation battery applications. Nickel-rich layered oxides such as LiNi0.8Mn0.1Co0.1O2 (NMC 811), are popular cathodes due to their high energy densities. However, they suffer from high surface reactivity, which results in the formation of Li2CO3 passive layer. Herein, we show the role of nanosecond pulsed laser annealing (PLA) in improving the current capacity and cycling stability of LIBs by reducing the carbonate layer, in addition to forming a protective LiF layer and manipulating the NMC 811 microstructures. We use high-power nanosecond laser pulses in a controlled way to create nanostructured surface topography which has a positive impact on the capacity retention and current capacity by providing an increased active surface area, which influences the diffusion kinetics of lithium-ions in the electrode materials during the battery cycling process. Advanced characterizations show that the PLA treatment results in the thinning of the passive Li2CO3 layer, which is formed on as-received NMC811 samples, along with the decomposition of excess polyvinylidene fluoride (PVDF) binder. The high-power laser interacts with the decomposed binder and surface Li+ to form LiF phase, which acts as a protective layer to prevent surface reactive sites from initiating parasitic reactions. As a result, the laser treated cathodes show relative increase of the current capacity of up to 50%, which is consistent with electrochemical measurements of LiB cells.

Spatiotemporal shaping of high power laser pulses based on stimulated brillouin scattering

We proposed and numerically demonstrated the combination of temporal and spatial shaping of high power nanosecond laser pulses based on stimulated Brillouin scattering (SBS) in this paper. With the intensity-dependence characteristic of SBS, the higher intensity parts of the laser beam obtain higher reflectivity, and the incident non-uniform high power laser beam would be well smoothed. A parameter adjustable feedback control loop was used to tailor the output temporal profile by pre-compensating the temporal profile of the input pump. In our numerical simulation, a 3 ns super-Gaussian shaped single-frequency laser pulse with a 527 nm wavelength was used as the pump. And the heavy fluorocarbon FC-70 was chosen as the Brillouin medium. Simulation results show that the laser spatial modulation can be significantly pulled down when the energy efficiency is maintained above 90% in our beam smoothing system with suitable laser intensity. The flat-toped laser pulses both in temporal and spatial domain were demonstrated to be achievable simultaneously. The method proposed here paves a simple and effective way to optimizing the near field pattern and temporal shape of high power laser systems.