Nanosecond Pulse Generator Research Articles

Extending mid-infrared wavelength to 6.84 μm in oxide nonlinear optical crystal via birefringence dispersion management.

Extending lasing wavelengths to the mid-infrared (MIR) spectrum is vital for both civilian and military applications; however, it remains challenging when employing oxide nonlinear optical crystals. In this study, we report the generation of MIR nanosecond pulses via difference frequency generation (DFG) with a near-IR pump using a newly designed langasite (LGS) crystal, La3(Nb0.6Ta0.4)0.5Ga5.5O14 (LGNT0.4), which incorporates birefringence dispersion management techniques with La3Ga5.5Nb0.5O14 (LGN) as a template. Due to the improved effective nonlinear coefficients and the maintained IR cutoff relative to LGN, the tunable DFG laser in LGNT0.4 extended from 4.24 to 6.84 μm, delivering a maximum pulse energy of 16.3 μJ at 5.02 μm. To the best of our knowledge, this is the first known oxide material capable of generating tunable nanosecond pulsed lasers beyond 6 μm at μJ-level energies, demonstrating promising potential for high-intensity MIR laser systems owing to its high laser damage threshold.

Review of Nanosecond Pulse Generator With High-Power Switching Devices

Review of Nanosecond Pulse Generator With High-Power Switching Devices

Design of an Electronic Interface for Single-Photon Avalanche Diodes.

Single-photon avalanche diodes (SPADs) belong to a family of avalanche photodiodes (APDs) with single-photon detection capability that operate above the breakdown voltage (i.e., Geiger mode). Design and technology constraints, such as dark current, photon detection probability, and power dissipation, impose inherent device limitations on avalanche photodiodes. Moreover, after the detection of a photon, SPADs require dead time for avalanche quenching and recharge before they can detect another photon. The reduction in dead time results in higher efficiency for photon detection in high-frequency applications. In this work, an electronic interface, based on the pole-zero compensation technique for reducing dead time, was investigated. A nanosecond pulse generator was designed and fabricated to generate pulses of comparable voltage to an avalanche transistor. The quenching time constant (τq) is not affected by the compensation capacitance variation, while an increase of about 30% in the τq is related to the properties of the specific op-amp used in the design. Conversely, the recovery time was observed to be strongly influenced by the compensation capacitance. Reductions in the recovery time, from 927.3 ns down to 57.6 ns and 9.8 ns, were observed when varying the compensation capacitance in the range of 5-0.1 pF. The experimental results from an SPAD combined with an electronic interface based on an avalanche transistor are in strong accordance, providing similar output pulses to those of an illuminated SPAD.

Nanosecond-pulse fiber laser mode-locked with iron phthalocyanine

Abstract In this paper, we demonstrated a passively mode-locked erbium doped fiber laser (EDFL) using iron phthalocyanine (FePc) material as a saturable absorber (SA). The FePc-SA was prepared via a casting method, integrating FePc powder with polyvinyl alcohol to form FePc-PVA film. When implemented into the mode-locked EDFL cavity, the laser generated 356 ns pulses at a repetition rate of 969 kHz. Operating at a wavelength of 1559 nm, the laser achieved pulse energy of 6.04 nJ, output power of 5.85 mW, and peak power of 0.014 W under a maximum pump power of 128.92 mW. The laser exhibited remarkable stability, evidenced by a signal-to-noise ratio of 71.7 dB at the fundamental frequency. These results demonstrate that FePc material effectively serves as a mode-locker for generating nanosecond pulses.

Nanosecond pulse electric field treatment initiates mitochondrial apoptosis pathway by inducing mitochondrial morphological changes in myocardial cells.

As an emerging myocardial ablation technique, the mechanism of nanosecond pulse electric field (nsPEF) ablation is currently less studied. Mitochondria are one of the important membrane structure organelles in cells, participating in numerous life activities within the cell. This study aimed to explore the morphological changes of mitochondria in living cells following nsPEF treatment. Myocardial cells were treated with a self-made solid-state LTD high-voltage nanosecond pulse generator with a pulse width of 100ns for 80 times. The changes in mitochondrial membrane potential and cell apoptosis in rat myocardial cells after nsPEFs were investigated using JC-1 assay kit, apoptosis double staining assay kit, and mitochondrial fluorescence probe. The results showed that after nsPEF treatment, the mitochondrial membrane potential decreased, apoptosis increased, and the average mitochondrial area decreased from 0.48 µm2 in live myocardial cells to 0.16 µm2. The average circumference ranges from 3.17µm dropped to 1.60µm. The shape factor decreased from 1.92 to 1.41. The aspect ratio has decreased from 2.16 to 1.59. nsPEF treatment induces changes in the morphology of myocardial cell mitochondria. Based on the results of mitochondrial membrane potential and apoptosis, it can be inferred that under this equipment and parameter conditions, nsPEF treatment first causes changes in mitochondrial morphology, and then initiates the mitochondrial apoptosis pathway, which may provide experimental basis for investigating the potential mechanism of nsPEF ablation of myocardial cells.

Development of All Solid State Nanosecond Pulse Transformer Fault Detection Device Based on Marx Circuit

Abstract a nanosecond pulse generator with a fast leading edge for transformer fault diagnosis is developed. The device is composed of a full solid-state nanosecond pulse generator based on Marx circuit and with a tail cut switch and a field programmable logic gate array (FPGA) device. Among them, the nanosecond pulse source is mainly composed of DC power supply, control circuit and main circuit. The main circuit is a 9-level modular Marx circuit, using MOSFET as the main switch and tail cut switch; The control circuit generates a synchronous trigger pulse signal, which drives the MOSFET to work synchronously after being isolated through the optical fiber. The output nanosecond pulse voltage parameters are adjustable amplitude 0-8kv, pulse width 100˜1000ns, repetition frequency 1hz˜1000hz, rising edge 30ns and falling edge 40ns. The transformer fault diagnosis platform is built, and the transformer off-line and on-line fault diagnosis is carried out, which paves the way for further exploration of transformer fault diagnosis technology.

Nanosecond pulse generation mode-locked by an artificial saturable absorber based on SMF-MMF-SMF structure

We present a noteworthy demonstration of nanosecond pulse generation utilizing an all-fiber artificial saturable absorber (SA) structure, composed of single-mode multimode single-mode fiber (SMF-MMF-SMF), integrated into a passively mode-locked erbium-doped fiber laser (EDFL). The SMS-based SA effectively phase-locked the longitudinal modes within the elongated EDFL cavity, resulting in the production of mode-locked pulses operating at 1567 nm. Mode-locking is achieved through the Kerr effect of nonlinear multimode interference. The pulse repetition rate is synchronized with the fundamental frequency at 1.28 MHz. At a pump power of 269.1 mW, the laser achieves a remarkable peak average pulse energy of 6.0 nJ. Demonstrating outstanding stability, the laser operation exhibits a peak-to-pedestal extinction ratio of 70 dB for the fundamental frequency. We are confident in the substantial potential of this SMS structure, positioning it as a compelling candidate for integration into ultrafast fiber lasers, with promising prospects in the field.

Nanosecond Pulse Generation in the C-Band Region Using Silver Sulfide as a Saturable Absorber

Nanosecond Pulse Generation in the C-Band Region Using Silver Sulfide as a Saturable Absorber

A 500-kV Nanosecond Pulse Generator Based on an Off-the-Shelf Solid-State Opening Switch

A 500-kV Nanosecond Pulse Generator Based on an Off-the-Shelf Solid-State Opening Switch

Compact Nanosecond Pulse Generator Based on Distributed Inductive Energy Storage of Twisted Pair Wire

Compact Nanosecond Pulse Generator Based on Distributed Inductive Energy Storage of Twisted Pair Wire

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.

Generation of Sub-Gigawatt Nanosecond Pulses of Microwave Radiation Based on a Coaxial Corrugated Transmission Line with Ferrite

Generation of Sub-Gigawatt Nanosecond Pulses of Microwave Radiation Based on a Coaxial Corrugated Transmission Line with Ferrite

New concept of two-cascade energy compression systems based on drift step recovery diodes

A new concept of effective high-voltage nanosecond pulse generators based on two compression cascades of drift step recovery diodes (DSRDs) is presented. The main advantage of the proposed approach arises from the decoupling of the operation cycles of DSRD cascades while using a single primary switch. This greatly improves the overall efficiency of the system. The first DSRD cascade operates with low pulse current densities. Its operation cycles can be extended resulting in an increase of the compression factor and pulse energy, whereas the loss level is kept at a minimum. The second DSRD cascade operates with high current densities, but the duration of its cycles can be chosen much shorter which ensures good efficiency too. Furthermore, an extension of the working cycle of the first DSRD cascade makes the requirement for the primary switch milder so that even relatively slow low-voltage switches can be employed.

Influence of avalanche transistor switching mode on waveform characteristics of solid-state pulse source.

The design of the Marx circuit based on avalanche transistors (ATs) is one of the effective techniques for developing solid-state pulse sources to generate nanosecond pulses. However, the influence of the avalanche transistor as a switching device on the output pulse characteristics is still unclear. In this study, investigating the switching mechanism of the AT with a mixed-mode simulation of the semiconductor device has been accomplished. An experiment has checked the simulation model's transient switching characteristics. The switching mechanisms of ATs in the Marx circuit were divided into base triggering mode (BTM) and voltage ramp mode (VRM). This paper proposes a modified circuit for adjusting the output pulse parameters of solid-state pulse sources. The results show that to satisfy the simulation accuracy, the width parameter of the AT model in the BTM must be 100μm, much less than the actual physical size. Because of the higher electric field when the initial impact ionization occurs, the AT operates at a higher switching speed in the VRM than in the BTM. In addition, since the carriers of initial impact ionization locate at the p-n0 interface or the n0-n+ interface, the AT switching process will oscillate in the VRM. All ATs in the modified Marx circuit switch to operate in the BTM. The leading edge of the output pulse increases from 275 to 1125ps, and the pulse trailing oscillation has disappeared. The research results provide an important technical means for optimizing the output waveform of solid-state pulse sources.

Hydrazone organics modulation for h-shaped nanosecond pulse generation in 1.3-km ultra-long mode-locked erbium-doped fiber laser

We report an ultra-long erbium-doped fiber laser based on hydrazone organisms that generates a tunable h-shaped pulse at the trailing edge and can readily convert nanosecond pulses into h-shaped pulse. By changing the polarization state in the cavity of the ultra-long laser, the nanosecond pulse can be converted to an h-shaped pulse at a certain power level. At this time, the pump power is increased, ranging from 208.2 mW to 393.2 mW, and the pulse trailing edge can be tuned regularly, with a tuning range from 8.2 ns to 17.9 ns. The experimental results show that the variation of the h-shaped pulse along the width is related to the clamping effect of the peak power and the weak birefringence effect. In conclusion, the investigation of ultra-long laser resonators based on real saturable absorbers is helpful to further explore the anomalous dispersion range of ultra-long round-trip pulses and their potential applications.

Multi-transversal mode pumping of narrow-bandwidth backward wave optical parametric oscillator.

A stable, narrow-bandwidth (274 MHz) backward wave optical parametric oscillator (BWOPO) generating mJ-level backward signal at 1885nm and forward idler at 2495 nm is presented. The BWOPO was pumped by a single-longitudinal mode, Q-switched Nd:YAG high-energy laser at 1064 nm. We show that multi-transversal mode pumping leads to the spectral broadening of the BWOPO backward signal and the generation of nanosecond pulses 2.7 times above the Fourier transform limit. We demonstrate over 100 GHz continuous tuning of the parametric output by adjusting the temperature of the BWOPO crystal, showcasing the significant role of thermal expansion in tuning performance. The BWOPO signal was used as a seed for a single-stage PPRKTP optical parametric amplifier (OPA) to boost the narrowband signal and idler energies to 20 mJ. This combination of mJ-level BWOPO seed with a single-stage PPRKTP OPA comprises a simple concept that would benefit long-range differential absorption lidar (DIAL) in the near and mid-infrared regions.

A Compact High-Stability Nanosecond Pulse Test System Using Corona-Stabilized Switch and Coaxial Resistance Divider

Due to the lack of a standard nanosecond high-voltage pulse generator for sensor calibration, a high-stability nanosecond high-voltage pulse test system was developed in terms of circuit analysis, structural design, and performance test. By establishing the equivalent circuit model of the nanosecond pulse generator, the circuit component parameters of the five-stage Marx loop and the one-stage compression steepening unit were simulated. The influence of the action performance of the steepening gap on the characteristics of output nanosecond pulse was analyzed. The nanosecond pulse test system was established through the structural design of the nanosecond pulse-generating circuit, the development of a high-performance corona-stabilized switch, and the measurement of a fast-response resistance divider made of metal oxide thin-film resistors. The nanosecond pulse test system has the capability to output a double exponential nanosecond pulse voltages in the amplitude range of 10–60 kV with a rise time of 2.3 ± 0.5 ns and a half-peak time of 23 ± 5 ns. In addition, the output pulse voltage has a high consistency and stability in the full amplitude range. The maximum relative standard deviation of the peak value is 1.517%, and the relative standard uncertainty is less than 5‰.

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.

Simulation study on beam chopper for an intense nanosecond pulsed neutron generator

This article reports about the design of the beam chopper for building up an intense nanosecond pulsed neutron generator, and the scheme of the accelerator and the features of its basic systems are presented. The effects of the fringing electric field of the sweeping plates and the space charge effect of the beam on the pulse duration and the emittance of the deuteron beam are studied. The chopper with an operating angular frequency of 60 MHz and the amplitude of the RF voltage is 1 kV, and it will transport deuteron beam with current of 5 mA and energy of 400 keV. The simulation results show that the full width of maximum height is about 12 ns when considering the space charge effect of the beam. However, the full width of maximum height is about 6 ns when the beam without the space charge effect. Compare to the calculated values and the simulation results, it is illustrated that the space charge effect plays an important role in the pulse width which produced by the chopper for the beam of current of several mA.

Broadband nanosecond pulse generation modulated by zirconium triselenide nanoflakes

Broadband nonlinear optical modulators are necessary for versatile applications in optical communication, laser radar, laser manufacturing, etc. Here, we report that the zirconium triselenide (ZrSe3) nanoflakes exhibit robust broadband nonlinear optical absorption and can modulate the Nd:YVO4 solid-state laser and erbium-doped ZBLAN fiber laser to deliver stable nanosecond pulse experimentally. The ZrSe3 nanoflakes have been prepared by the liquid phase exfoliation method successfully and exhibit broadband nonlinear optical absorption in the near-infrared and the mid-infrared regime. With the nonlinear absorption performance of the ZrSe3 nanoflakes, stable pulsed operation has been achieved with the output pulse width as short as 344.68 ns around 1 µm from the Q-switched Nd:YVO4 solid-state laser and 599 ns around 2.8 µm from the erbium-doped ZBLAN fiber laser successfully. The experimental results suggest that ZrSe3 nanoflakes can act as an excellent nonlinear optical modulator towards the mid-infrared regime and may make inroads toward developing high-performance broadband optoelectronic devices.