Nanosecond Pulse Generator Research Articles

Sub-hundred nanosecond pulse generation from a black phosphorus Q-switched Er-doped fiber laser.

Black phosphorus (BP), a prosperous two-dimensional optoelectronic material, has been deeply developed for various optoelectronics applications. Here, we demonstrate a sub-hundred nanosecond passively Q-switched Er-doped all-fiber laser with BP as the saturable absorber (SA). The BP-SA is fabricated by a controllable optical deposition technique. To achieve the sub-hundred nanosecond Q-switching output, we deliberately enlarge the modulation depth of the BP-SA by suitably increasing the time and laser power of the optical deposition and shortening the laser cavity length with an integrated multifunctional component. A stable Q-switched pulse train was obtained with a pulse duration as narrow as 91 ns, and the Q-switched lasing characteristics based on the BP-SA have also been investigated and discussed. The experimental results indicate that the BP material can be employed as an effective SA for the nanosecond pulse generation.

Self-Triggering High-Frequency Nanosecond Pulse Generator

With the increasingly extensive and in-depth applications of all solid-state high-voltage nanosecond pulse generators in the defense and industrial fields, the development of traditional pulse generators faces many key issues, such as high-voltage drive isolation, compact design, and reduced weight. Hence, a novel circuit topology for a self-triggered high-frequency nanosecond pulse generator is proposed. Through high potential energy-gaining technology of the interstage capacitance, this generator does not need a complicated metal–oxide–semiconductor field-effect transistor isolation drive circuit, and there are also no switching dynamic and static voltage equalization problems. This kind of generator is very suitable for compact assembly with only a single external gate driver. High voltage output can be realized by quantizing multilevel module stacking according to actual needs. At the same time, the generator has a high repetition rate and long life. The characteristic parameters of the 20-stage superposition experimental prototype are as follows: an output voltage amplitude of 15.3 kV with a rising time of approximately 45 ns, a repetition rate of 10 kHz in the pulse train, and a pulsewidth of 200–1000 ns.

Compact nanosecond pulse generator based on IGBT and spark gap cooperation

Compact nanosecond pulse generator based on IGBT and spark gap cooperation

The activation of cancer cells by a nanosecond-pulsed magnetic field generator

Cancer treatment is a challenge in modern medicine. Several novel modalities have been invented to selectively treat cancer cells. The reactive species such as reactive oxygen species and reactive nitrogen species play important role in the anti-cancer capacity of several modalities, such as cold atmospheric plasma. In this study, we first demonstrated that a nanosecond-pulsed magnetic field (NMF) generator could sensitize the melanoma cell line B16-F10 to the cytotoxicity of an important ROS, H2O2. The magnetic field strength and the frequency were two key factors to control the activation level of NMF treatment. This study provided a novel strategy to use electromagnetic modality in cancer treatment particularly for the treatment on deep tumors such as brain, pancreatic, etc.

A High Voltage Diode-Transistor Generator of Nanosecond High Voltage Pulses

A small generator of high-power high voltage nanosecond pulses with a 12 V power source is considered. At a load of 75 Ω, it provides the generation of pulses with an amplitude of ~17 kV, a front of ~4 ns, and an energy of ~15 mJ. The maximum pulse repetition rate is 15 kHz. The generator contains an inductive energy storage device and a capacitive storage device with an operating voltage of 1 kV. The formation of high voltage pulses is carried out by a high voltage current chopper in the form of a block of drift diodes with a sharp recovery. The conditions for the effective operation of the diodes are provided by a block of parallel-connected IGBT transistors with an operating voltage of 1.2 kV. The possibility of using a generator for multispark ignition of the spark plug of an internal combustion engine is shown.

Лазерно-индуцированный графен на полиимидной пленке: наблюдение эффекта увлечения

Porous graphene film structures were produced by irradiation of polyimide film with focused continuous wave CO2 laser. Generation of nanosecond pulses of photocurrent was observed in the obtained structures upon excitation by nanosecond laser pulses in a wide range of wavelengths. It is shown that the photocurrent linearly increases with pulsed laser power and its dependence on the angle of light incidence on the film structure is symmetric about the origin. Wavelength dependence of light-to-photocurrent conversion coefficient was measured. The obtained results are explained by photon-drag effect photocurrent generation.

Fundamental and harmonic mode-locked h-shaped pulse generation using a figure-of-9 thulium-doped fiber laser.

Herein, we present a fundamental and harmonic mode-locked figure-of-9 thulium-doped fiber laser using a nonlinear amplifying loop mirror. The generated fundamental mode-locked h-shaped pulse is centered at 1889 nm with an average output power reaching 282 mW and a pulse energy up to 1.23 µJ, which is the highest power and pulse energy of an h-shaped pulse. In the harmonic mode-locked regime, up to the 8th harmonic h-shaped pulse is obtained. The detailed characteristics of the h-shaped pulse are discussed. The proposed study shows that the figure-of-9 fiber laser can generate h-shaped pulses and also allows the generation of nanosecond pulses with a µJ-level pulse energy.

A Compact Series-Connected SiC MOSFETs Module and Its Application in High Voltage Nanosecond Pulse Generator

Nanosecond pulse discharge plasma has many prospects in industrial applications, and high-voltage repetitive nanosecond pulse generators with compact design and light weight have become one of the key issues limiting its development in some applications. This paper presents a high voltage series-connected silicon carbide (SiC) metal-oxide -semiconductor field effect transistor ( MOSFET s) module which can be served as the main switch in a repetitive high-voltage nanosecond pulse generator. This kind of series-connected MOSFET s module with only single external gate driver requiring very few components is very suitable for compact assembly. By analyzing the working principle, three topologies of series-connected MOSFET s module are proposed. The switching behaviors of the three different topologies with four SiC MOSFET s series-connected are compared experimentally. The variation of switching characteristics of series-connection SiC MOSFET s module with different numbers of devices are investigated. The layout is also optimized to shorten pulse front time and improve output pulse quality. Furthermore, a 10 kV SiC MOSFET s module with a turn- on transition time ∼10 ns is developed. The double pulse test result demonstrates excellent switching performances. Finally, a compact and high-voltage pulse generator composed of three 10 kV SiC MOSFET s module is tailored, with a typical rise time ∼40 ns and peak voltage of ∼30 kV.

High-Efficiency Relativistic Generators of Nanosecond Pulses in the Millimeter-Wavelength Range

We propose and study a scheme of a microwave pulse generator operating in the frequency ranges near 37 and 73 GHz, in which the electron interaction with both the (−1)st harmonic of the counterpropagating TM02 mode and the synchronous slowed-down TM01 mode is combined in a sectionalized slow-wave system with an average diameter of 2.5λ. An efficient current modulation at the input of the slow-wave system is ensured in the region of the cathode–anode gap and the matching section, which reduces the diffraction loss of the energy flow directed towards the cathode. Numerical modeling shows that the efficiency of converting the electron-beam power to microwave radiation is up to 50%. Experiments demonstrate a stable regime of generation of subgigawatt pulses at an efficiency of more than 40% in the upper part of the millimeterwavelength range, which have a reproducible spatial wave structure corresponding predominantly to the TM01 mode at the input of the emitting horn.

Semiconductor generator of high voltage nanosecond pulses for plasma technologies

A generator of nanosecond pulses is discussed in the paper. The main output parameters of the generator are as follows: the maximum output voltage amplitude is 20 kV, the output current strength is 300 A, the maximum frequency is 3 kHz, the output pulse rise time is 4 ns, the output pulse energy is 25 mJ. The generator is based on a current interrupter, which is an assembly of drift step recovery diodes (DSRD). Effective operation of the DSRD is provided by assemblies of IGBT-transistors connected in series, the operating voltage of each assembly is 4 kV. It is shown that the generator can be effectively used for purification of air from organic pollutants and for ignition of car spark-plugs.

An improved pulsed electroacoustic system for space charge measurements under high temperatures and arbitrary waveform voltages

This paper presents the design and calibration method of an improved pulsed electroacoustic (PEA) system for space charge measurements, including a novel nanosecond pulse generator and an improved electrode system, which can be used under various temperatures and arbitrary waveform voltages. The measurement principle of the PEA system is first analyzed, and the calibration method for the applied voltage is proposed to solve the problem of waveform distortion caused by voltages with different frequency components. For the pulse generator, the main parameters of output pulses are an amplitude of ∼700 V, a full width of 4.6 ns, a jitter of 0.24 ns, and a repetition rate of 10 kHz on the 50 Ω load. For the electrode system, the flexible upper electrode design is first introduced to achieve consistently close contact between the sample and the electrode. Besides, the hybrid heating method and the replaceable coupling capacitor and high voltage electrode head are adopted. Space charge measurements are conducted at different conditions using this PEA system, which includes different temperatures and different voltage waveforms. The experimental results verify the effectiveness of the calibration method and the feasibility of the improved PEA system.

Gain-switched dysprosium fiber laser tunable from 2.8 to 3.1 μm.

We demonstrate a tunable gain-switched Dy3+-doped ZBLAN fiber laser around 3 μm, for the first time, to the best of our knowledge. The pump source is a homemade actively Q-switched Yb3+-doped silica fiber laser at 1.1 μm, yielding a repetition rate of 80 kHz and a pulse width of 300 ns. A plane-ruled grating in a Littrow configuration functions as the tuning element. At the launched pump power of 2.78 W, stable gain-switched pulses tunable within a ~300 nm range of 2800~3095 nm are achieved. When tuning the wavelength to 2946.5 nm, a maximum output power of 218.6 mW with a repetition rate of 80 kHz is obtained. The corresponding pulse width and energy are 530 ns and 2.73 μJ, respectively. The results imply that gain-switching of Dy3+-doped ZBLAN fiber laser is an alternative way for mid-infrared nanosecond pulse generation around 3 μm.

MXene saturable absorber for nanosecond pulse generation in a mid-infrared Ho,Pr:LLF bulk laser

In this paper, high quality few-layer MXene-Ti3C2Tx was fabricated by the LPE method and successfully applied as saturable absorber for a passively Q-switched (PQS) Ho,Pr:LLF laser operating at 2.95 µm. The maximum average output power was determined to be 105 mW with a slope efficiency of 5%. The shortest pulse width and the largest pulse repetition rate were determined to be 266.7 ns and 83.24 kHz, corresponding to the single pulse energy and pulse peak power of 1.26 µJ and 4.73 W, respectively. It is the first demonstration of MXenes applied in mid-infrared (MIR) PQS solid-state bulk lasers, to the best of our knowledge. The results not only verify the broadband nonlinear saturable absorption properties of MXenes, but also pave the way for exploring their applications in photonic devices.

An overvoltage driver with inductive adder pulse for fast switching of series-connected MOSFETs module

A novel overvoltage driver is proposed to speed up the turn-on transition of series-connected MOSFETs module which serves as the main switch in high voltage pulse generator. In order to realize the overvoltage driver, a nanosecond pulse with the amplitude of hundreds of volts is superposed on a square driving signal by linear transformer driver scheme. The results show that, comparing to the commercial high current driver, the turn-on time of a 10kV MOSFETs module including ten devices with the proposed driving scheme can be shortened from ∼25ns to ∼7ns. The proposed overvoltage driver can be used to conveniently modulate the rise time and pulse width of high voltage nanosecond pulse generator constructed by MOSFETs. In addition, it is demonstrated that there is almost no influence of the overvoltage driver on the gate-source characteristics of device by analyzing the variation of C-f curves of input capacitances.

Nanosecond pulses generation with rose gold nanoparticles saturable absorber

We demonstrate a mode-locked nanosecond erbium-doped fiber laser using gold nanoparticles saturable absorber. The gold nanoparticles were obtained through sodium borohydrate reduction method and made into a film structure by embedding into poly (vinyl alcohol). The laser directly produces nanosecond pulses with stable mode locking at a pump threshold of 157 mW. Resultant output pulses have central wavelength, pulse duration and repetition rate of 1561 nm, 436 ns and 1 MHz, respectively. The average output power was measured to be 6.94 mW under the pump power of 245 mW, corresponding to single pulse energy of 6.8 nJ. The experimental results show that gold nanoparticles are a promising material for ultrafast laser systems.

Nanosecond Pulses Generation with Samarium Oxide Film Saturable Absorber**Supported by the INTI Research Grant Scheme 2018 under Grant No INTI-FITS-01-06-2018.

Nanosecond pulse generation is demonstrated in a mode-locked erbium-doped fiber laser (EDFL) utilizing a samarium oxide (Sm2O3) film. The Sm2O3 film exhibits a modulation depth of 33%, which is suitable for mode-locking operation. The passively pulsed EDFL operates stably at 1569.8 nm within a pumping power from 109 to 146 mW. The train of generated output pulses has a pulse width of 356 nm repeated at a fundamental frequency of 0.97 MHz. The average output power of 3.91 mW is obtained at a pump power of 146 mW, corresponding to 4.0 nJ pulse energy. The experimental result indicates that the proposed Sm2O3 saturable absorber is viable for the construction of a flexible and reliably stable mode-locked pulsed fiber laser operating in the 1.5 μm region.

High-Voltage Diffused Step Recovery Diodes: II. Theory

Approximate analytical formulas are derived to evaluate the main characteristics of diffused step recovery diodes, which operate as current interrupters in high-power nanosecond pulse generators with intermediate inductive energy storage: the spurious prepulse voltage, characterizing the resistive loss in diffused step recovery diodes; amplitude; front duration; maximum voltage rise rate, and duration of the pulse formed on an active load. Similar formulas for epitaxial step recovery diodes, partially obtained for the first time and partially refining previous results, are given for comparison.

High-Voltage Diffused Step Recovery Diodes: I. Numerical Simulation

The operation of diffused step recovery diodes (dSRDs) as current interrupters in high-power nanosecond pulse generators is studied in detail for the first time by numerical computer simulation. One of the necessary conditions for minimizing the loss in dSRDs is specified. The dependences of the prepulse voltage, front duration, amplitude and duration of the pulse formed on a resistive load, and the switching-loss energy in a dSRD on the device area and break current density are obtained. It is shown that the simulation results can be described by simple analytical formulas obtained in the second part of the work with an error of 10–20% if the pulse amplitude does not exceed the dSRD avalanche breakdown voltage. A generalized figure of merit of dSRDs is proposed, which can be used to optimize the dSRD parameters and operation mode and compare the efficiency of current interrupters of different types.

High-Power Nanosecond Pulse Generators With Improved Reliability by Adopting Auxiliary Triggering Topology

Marx bank circuits (MBCs) based on avalanche transistors are widely used to generate nanosecond pulses with high power, high repetition rate, and low jitter. However, it was observed that avalanche transistors in the first and second stages of traditional M × N -stage MBCs have high failure rates. This paper proposes an auxiliary triggering topology (ATT) for improving the reliability of high-power MBCs based on avalanche transistors. The operation principles of ATT and failure mechanisms of traditional MBCs are analyzed. By adopting ATT, the auxiliary triggering pulse is generated between the base and emitter of the transistor, and the switching mode is changed from “overvoltage switching- on ” to “triggering switching- on . ” The combined effect of overvoltage ramp and auxiliary triggering pulse significantly reduces the failure rate and prolongs the lifetime of easily damaged transistors. Two high-power nanosecond pulse generators, 3 × 12-stage and 6 × 10-stage MBCs adopting ATT, are developed to verify the feasibility of the proposed configuration. The output amplitude and the rising time are 8.5 kV/6 ns and 17 kV/6 ns at the open end of coaxial cable with 75-Ω impedance, respectively. Both generators are tested continuously at the repetition rate of 2 kHz for 60 min and no failure occurs, which shows much better performance in repetition rate and reliability than traditional M × N -stage MBCs.

Push–pull configuration of high-power MOSFETs for generation of nanosecond pulses for electropermeabilization of cells

AbstractA power MOSFET-based push–pull configuration nanosecond-pulse generator has been designed, constructed, and characterized to permeabilize cells for biological and medical applications. The generator can deliver pulses with durations ranging from 80 ns up to 1 µs and pulse amplitudes up to 1.4 kV. The unit has been tested for in vitro experiments on a medulloblastoma cell line. Following the exposure of cells to 100, 200, and 300 ns electric field pulses, permeabilization tests were carried out, and viability tests were conducted to verify the performance of the generator. The maximum temperature rise of the biological load was also calculated based on Joule heating energy conservation and experimental validation. Our results indicate that the developed device has good capabilities to achieve well-controlled electro-manipulation in vitro.