Search

To calibrate non-contact sensors with fast response and high scale factor, it is critical to develop step pulse generators capable of generating standard high voltage step pulses and accurately measuring the generated waveform. In this paper, two types of step pulse generators are designed with output voltages of 2 kV and 100 kV. The 2 kV step pulse generator can generate a step pulse with a rise time of ~300 ps and an adjustable pulse width. A step pulse with a rise time less than 5 ns and a pulse width over 1 s can be generated with the 100 kV step pulse generator. The uncertainty of 2 kV step pulse generator is then analyzed by simulations and experiments. Finally, a performance comparison with step pulse generators in previous studies is carried out. Bandwidth, linearity and repeatability of the sensors can be verified with the designed two step pulse generators.

In this work, the influences of P-well design and turn-off gate-to-source bias on the surge robustness of SiC MOSFET’s body diode are studied. Devices with high and low P-well doping concentration designs are stressed with surge current pulses when gate-to-source is biased with 0V or -5 V. The gate-to-source bias is found to have effects on the surge capability of the low P-well doping designed device. In the case of 0 V bias, the channel is prone to turning on and acquires a higher surge capability than the devices under the -5 V. On the other hand, the surge capability of high P-well doping designed device is found less influenced by the gate-to-source bias. Furthermore, threshold voltage instability after repetitive surge pulses is also investigated. The device with low P-well doping shows better threshold stability due to its lower interface trap density. Based on the results above, a design methodology is proposed from the view of device mechanism and operation condition. Relatively low P-well doping design and negative gate bias are recommended for SiC MOSFET, as they can improve the single pulse surge robustness of body diode and minimize the threshold voltage instability in repetitive surge pulse events.

Selective harmonic elimination pulsewidth modulation (SHEPWM) is a modulation technique widely used to improve the efficiency and harmonic content in medium-voltage high-power converters. Among these converters, the three-level neutral-point-clamped (3L-NPC) converter is one of the most utilized topologies. However, the 3L-NPC converter requires a proper balancing of dc-link capacitor voltages. This paper presents a control technique, based on pulse shifting method, to regulate the neutral point voltage when SHE-PWM is utilized. The proposed technique performs well with any power factor and it can also be directly applied to T-type converters and easily extrapolated to other multilevel topologies. The proposed method is experimentally validated in a scaled-down power converter and a full-scale medium-voltage 3L-NPC converter.

The intersecting cortical model (ICM), initially designed for image processing, is a special case of the biologically inspired pulse-coupled neural-network (PCNN) models. Although the ICM has been widely used, few studies concern the internal activities and firing conditions of the neuron, which may lead to an invalid model in the application. Furthermore, the lack of theoretical analysis has led to inappropriate parameter settings and consequent limitations on ICM applications. To address this deficiency, we first study the continuous firing condition of ICM neurons to determine the restrictions that exist between network parameters and the input signal. Second, we investigate the neuron pulse period to understand the neural firing mechanism. Third, we derive the relationship between the continuous firing condition and the neural pulse period, and the relationship can prove the validity of the continuous firing condition and the neural pulse period as well. A solid understanding of the neural firing mechanism is helpful in setting appropriate parameters and in providing a theoretical basis for widespread applications to use the ICM model effectively. Extensive experiments of numerical tests with a common image reveal the rationality of our theoretical results.

This article presents the spatial and temporal dynamics of high-power Gaussian laser pulse in relativistic plasma. At higher intensities, the self-focusing and self-compression of laser pulse take place due to the variation in the mass of plasma electrons moving with speed comparable to the speed of light. The two non-linear coupled differential equations for spatial and temporal pulsewidth parameters have been obtained using the moment theory approach. These equations have been solved numerically using the Runga-Kutta method. The variation in the spatial and temporal pulsewidth parameters with the distance of propagation is then used to calculate the energy gained by the electrons, which are trapped by the excited electron plasma wave during laser-plasma interaction. It is observed that spatio-temporal dynamics play an important role in electron acceleration in relativistic plasma.

Deinterleaving mixtures of radar pulse sequences is the first and the most vital step for modern electronic reconnaissance systems to intercept and analyze the intentions of non-cooperative radars. Currently, these systems are facing great challenges due to the emerging complexity of radar modulations. This paper proposes a novel method for deinterleaving mixtures of radar pulse sequences based on the time series characteristics of each source (component pulse sequences). Firstly, the mathematical representations are established to describe the structural characteristics of each source. Then, the deinterleaving problem is formulated as a minimization of a maximum-likelihood cost function that can be solved efficiently through a supervised neural machine translation (NMT) network, i.e. to translate each received pulse in the interleaved pulse sequence to the corresponding source label. A sequence-to-sequence NMT model is proposed to capture the structural relationships among the non-adjacent pulses originated from the same source in the mixtures and assign the corresponding label to each pulse. The proposed method does not require the exact knowledge of each component pulse sequence. The experimental results based on the time of arrival sequence of mixed pulse sequences show that the proposed method outperforms the state-of-the-art deinterleaving methods and achieves satisfactory performance under highly non-ideal situations with measuring noise and lost pulse conditions. The proposed method can be directly applied to other fields involving deinterleaving problems and multi-variate input conditions.

We firstly propose a roadmap for the design of high repetition rate (~100 MHz) Tm-doped ultrafast fiber laser with an emission wavelength above 2000 nm. This roadmap is confirmed by both theoretical simulation and experimental verification. The designed Tm-doped fiber oscillator not only operates in continuous wave regime with a broad tunable wavelength range of ~ 100 nm, but also in mode-locking regime with an emission wavelength > 2000 nm (up to 2020 nm). A 470-fs laser pulse with a pulse repetition rate of ~96 MHz and the maximum average power of 50 mW are achieved at the output wavelength of 2007 nm, matching well with the theoretical prediction. In a further step, the seed laser pulse is amplified to 3.3 W, accompanied by a Raman frequency shift of the output wavelength to 2346 nm. The homogeneous intense broadband spectrum with a bandwidth of 240-nm centered at 2200 nm is also observed.

Although pulse charging strategy has many advantages, it is still controversial. The paradox is that it prolongs the charging time to eliminate the polarization voltage by the pulse interval, and the AC component in pulse current will increase the ohmic losses. In this paper, an optimal charging strategy with complementary pulse current of Lithium-ion is proposed to address and alleviate these issues. For the pulse frequency, the optimization can be achieved through the electrochemical impedance spectroscopy (EIS) analysis to reduce the battery’s AC impedance. For the pulse amplitude, based on the battery’s internal resistance characteristics, minimize the ohmic losses to obtain the optimal amplitude. For the pulse duty cycle, it is adjusted to achieve state of charge (SOC) balancing in the early charging stage, and battery’s terminal voltage balancing in the later stage. Based on the optimized charging strategy, a pulse charger concept is proposed, which can flexibly control the pulse charging currents and use complementary pulses to completely eliminate the prolonged charging time caused by the pulse interval. In the end, an experimental platform for pulse charger of lithium-ion batteries is designed, and the theoretical analysis is verified by the comparative experiments.

Bifurcation amplifiers are two-state systems that behave as flip-flops. We propose a two-bit shift register with coupled bidirectional bifurcation amplifiers. We consider a model of the amplifier that is based on a driven nonlinear vibrational system with Duffing nonlinearity. A discussed physical implementation is a nano-mechanical system. The analysis of bifurcation points provides a design framework for driving forces. We use a modulated two-level pulse at the first amplifier and a periodic three-level pulse at the second. We numerically demonstrate that these driving forces allow for the transfer of digital data between each amplifier. Our investigation provides an alternative approach for developing digital shift registers using nonlinear dynamics at the nanoscale.

International audience; In high dose per pulse charged particle beams, all online detectors saturate due to ion recombination. It is therefore impossible to count detector pulses separately. Silicon carbide due to its high band gap, high thermal conductivity and high displacement energy, is seen as an alternative. Analyzing waveforms in real time is challenging in terms of bandwidth, measurable energy range, sensor size, data rate. In this contexte, an Analog Front-End (AFE) was designed for radiation signal processing. It is based on a TransImpedance Amplifier (TIA) and Charge Sentitive Amplifier (CSA) to analyze the shape of generated signal. The methodology used to characterize AFE for high detector capacitance is described. The results extracted from simulations, experimental and measurements in radiative environment are also presented.

Acoustic levitation is considered one of the most effective noncontact particle manipulation methods, along with aerodynamic, ferromagnetic, and optical levitation techniques. It is not restricted by the material properties of the target. However, existing acoustic levitation techniques have some drawbacks that limit their potential applications. Therefore, in this article, an innovative approach is proposed to manipulate objects more intuitively and freely. By taking advantage of the transition periods between the acoustic pulse trains and electrical driving signals, acoustic traps can be created by switching the acoustic focal spots rapidly. Since the high-energy-density points are not formed simultaneously, the computation of the acoustic field distribution with complicated mutual interference can be eliminated. Therefore, compared to the existing approaches that created acoustic traps by solving pressure distributions using iterative methods, the proposed method simplifies the computation of time delay and makes it possible to be solved even with a microcontroller. In this work, three experiments have been demonstrated successfully to prove the capability of the proposed method including lifting a Styrofoam sphere, transportation of a single target, and suspending two objects. Besides, simulations of the distributions of acoustic pressure, radiation force, and Gor'kov potential were conducted to confirm the presence of acoustic traps in the scenarios of lifting one and two objects. The proposed tactic should be considered effective since the results of the practical experiments and simulations support each other.

Quantum cascade lasers are highly stable against optical feedback, where the reflection mirror is well aligned with the optical path. Therefore, it is challenging to produce pulse oscillations in quantum cascade lasers through normal optical feedback. In this work, we show that tilted optical feedback with a misaligned reflection mirror triggers quantum cascade lasers to generate low-frequency oscillations, including irregular pulse oscillations and square wave oscillations. The oscillation period is in the microsecond range, and generally decreases with increasing tilt angle. In addition, the duty cycle of the square waves is tunable through varying the tilt angle. It is also found that a weak feedback strength or a low pump current yields rare occurrence of the pulse oscillations.

A multistage signal estimation scheme is proposed for phase-and-amplitude modulated soliton communication systems. The estimator provides a significant mean-squared-error reduction in soliton amplitude estimation, which, in conjunction with detection of encoded phase information, results in spectral-efficiency improvements. A low-complexity version of the multistage estimation scheme is also proposed, whose performance is studied via numerical simulations under the distributed Raman amplification strategy. The achievable information rate is increased by about 1 bit/symbol for pulse bandwidth of 30 GHz, 40 GHz, and 50 GHz.

Under the frequency modulated continuous wave (FMCW) system, the “stop-and-go” echo model of traditional pulse synthetic aperture radar (SAR) is no longer applicable. The range-azimuth coupling term introduced by fast time going term cannot be ignored, or otherwise it will cause degradation in the quality of generated image. This paper proposes a Sliding Spotlight SAR imaging algorithm based on improved two-step method. To address the problems of big interval of FMCW SAR and difference from the pulse SAR echo model triggered by dechirp reception, the proposed algorithm has improved the ωk algorithm and realized great focusing of FMCW signal. Furthermore, this algorithm adopts the method of focusing azimuth deramp in frequency domain to prevent the aliasing problem in image domain encountered by the classic two-step method. The simulation and real data results prove that this method can realize good focusing of FMCW SAR Sliding Spotlight mode.

We propose an all-fiber passively mode-locked laser for high-purity high-order mode generation by combining a two-mode long period fiber grating (TM-LPFG) and a two-mode fiber Bragg grating (TM-FBG). The grating combination fully plays respective advantages: highly efficient mode conversion of the LPFG, mode selection and spectrum filtering of the TM-FBG. A semiconductor saturable absorber (SESAM) is used to achieve passively mode-locking. As a result, the mode-locked cylindrical vector beam (CVB) pulse with a 3-dB spectral width of 0.08 nm at a repetition rate of 12.88 MHz has been obtained, and the signal to noise ratio (SNR) is as high as 68 dB. Moreover, the azimuthally and radially polarized CVBs obtained after degeneracy elimination have high purity of 95.6% and 98.3%, respectively. This laser may have the potential for generation of high-purity CVB pulse.

International audience; Many-particle time domain methods are rising alternatives to particle-in-cell (PIC) or frequency methods to simulate the wave–beam interactions in traveling wave tubes (TWTs). We focus on two of those: our Hamiltonian discrete model DIMOHA is compared analytically against the pseudospectral method RUBEUS. Although based on two completely different approaches—the Gel’fand transform for DIMOHA and the telegraphist circuit for RUBEUS—we surprisingly find out that they share perfectly parallel sets of equations and variables. However, we conclude that DIMOHA is more flexible than RUBEUS in terms of pitch tapering and absorbing boundary conditions. It also shows excellent stability for steady-state simulation, allowing us to explain some discrepancies of RUBEUS with experimental results. These come from a standing wave pattern which is detectable in the vicinity of the sever. Finally, DIMOHA is tested for the first time with ultra-short pulses and exhibits excellent agreement with RUBEUS.

Dynamic degradation becomes a critical issue for thin-film transistors (TFTs) used in emerging new displays driven by high frequency gate voltage ${V}_{\text {G}}$ pulses. In this study, ${V}_{\text {G}}$ pulse rising edge dependent dynamic hot carrier degradation of poly-Si TFTs is investigated. It is demonstrated that rising edge of ${V}_{\text {G}}$ pulses which swing within the OFF-state of TFTs causes the degradation, while that of normal ${V}_{\text {G}}$ pulses which switch between the ON and OFF states across the flat band voltage ${V}_{\text {FB}}$ of TFTs does not. Based on transient TCAD simulation, the underlying mechanism of rising edge dependent degradation is proposed, which is based on the non-equilibrium PN junction degradation model previously proposed to explain ${V}_{\text {G}}$ pulse falling edge dependent degradation of poly-Si TFTs. Hence, the dynamic degradation model of poly-Si TFTs related to both rising and falling edge of the ${V}_{\text {G}}$ pulses can be unified now, which is applicable to fast gate pulses with steep rising and/or falling edges in sub- $\mu \text{s}$ level.

Nonlinear transmission lines (NLTLs) provide a means to generate high-repetition-rate, high-power microwaves with fewer auxiliary systems than conventional sources. They are typically driven by pulse forming networks (PFNs) or Marx generators, and one would intuitively hypothesize that the microwave generation would not depend significantly on the method used to generate the input pulse to the NLTL. This study examines the implications on microwave output by using a Blumlein pulse generator with a 10-ns pulse duration and 1.5-ns rise and fall times to drive coaxial NLTLs produced using composites with nickel zinc ferrite and barium strontium titanate (BST) inclusions. Applying a 30-kV pulse to the composite NLTLs produced frequencies ranging from 1.1 to 1.3 GHz with output powers over 20 kW. The output frequencies increased with increasing volume fraction of BST. Measured results and simulations using LT SPICE showed that Blumlein modulators were insufficient to drive NLTLs to produce high-power oscillations; however, LT SPICE simulations showed that applying a standard PFN to the same NLTL produced the expected oscillations. This difference arises because the mechanism for Blumlein pulse formation cancels the shockwaves responsible for inducing microwave production by the NLTL.

Ultra-short pulse lasers, generating coherent light pulses with pulse durations in the picosecond and femtosecond range, are becoming popular in precision laser microfabrication. They are benefiting not only from well-predicted laser ablation with the suppressed heat-affected zone but also by opening new processing opportunities, especially in transparent materials, due to enhanced non-linear interaction with the material. In this review, the evolution of various kinds of mode-locked lasers from a scientific toy to a robust industrial tool is reviewed. The utilization benefits of high-average-power, high-pulse-repetition-rate ultra-short pulse laser are closely related to beam shaping and manipulation techniques. Fast beam scanning with galvanometric and polygon scanners as well as multi-beam parallel processing methods were developed. Some hot applications areas are briefly described. The efficient use of photons from ultra-short pulse lasers pushed the development of optimization methods in the ablation process. Efforts toward upscaling the process by increasing the average power of mode-locked lasers made feedback to laser developers, and burst regime became a necessity as well as high-speed beam scanning devices. Unique opportunities of ultra-short pulses are successfully exploited in machining transparent materials, with glass separation being the leading application.

A high-energy Mamyshev oscillator was experimentally demonstrated with an all polarization-maintaining 10/125 fiber configuration, which is initiated by an external pulse radiation. A maximum output power of 787.3 mW with the single pulse energy of 83.5 nJ was achieved at a repetition rate of 9.43 MHz. The pulse width was compressed to 56 fs with a grating pair, corresponding to a peak power of 1.15 MW considering the insertion loss of the grating pair. The evolution of the pulse properties versus the enhancement of the energy was examined and an excellent long-time stability was verified. It is believed that such a compact all-fiber ultrafast oscillator could be a promising source for practical applications such as material processing, medicine, nonlinear microscopy and so on.

Distributed optical fiber vibration sensor (DOFVS) is suitable for remote monitoring of vibration signals generated by external perturbations. In order to improve the sensing performance, various pulse coding techniques are applied in DOFVS, which have attracted an increasing amount of research attention. In this paper, recent advances of pulse coding methods used in DOFVS are reviewed, from pulse compression, including linear frequency modulation (LFM) and nonlinear frequency modulation (NLFM), pulse coding modulation based on the linear combination and correlation operation, such as Simplex code, Golay code and random code, as well as pulse sequence modulation (PSM), such as phase-shift pulses, differential frequency pulses, etc. Characteristics, working principles and the latest research results of pulse coding methods are discussed. Furthermore, some application progresses of pulse coding for performance enhancement in DOFVS are also introduced. By combining these technologies, the sensing performance could be improved in aspects of sensing distance, spatial resolution (SR), and frequency response, which show considerable potential applications in perimeter security, oil and gas monitoring, pipeline leakage, and structural health monitoring.

All solid-state microchip lasers having the advantage of short cavity lengths give them tremendous potential as pulsed devices for short pulse laser generation. In this work, by constructing a compact microchip-like laser resonator, we have demonstrated continuous-wave (CW) Pr,Mg:SrAl12O19 (SRA) lasers at 622 nm and 643 nm, respectively with maximum output powers of 0.69 W and 1.18 W with excellent beam qualities, which is believed to be the highest powers that have achieved in Pr3+ microchip lasers. Based on this CW opeation, we, by using a Co:LMA saturabel absorber, have further demonstrated passively Q-switched operation of the two lasers. The shortest pulse widths reached about 28.5 ns (for the 622 nm laser) and 31.9 ns (for the 643 nm laser), which are relatively short pulse time durations for passively Q-switched Pr3+ lasers thanks to the compact laser configuration. This work has proposed a simple route for achieving compact high-power CW and short-pulse Q-switched visible lasers.

We characterize the frequency response of channel-interleaved photonic analog-to-digital converters (CI-PADCs) theoretically and experimentally. The CI-PADC is composed of a photonic frontend for photonic sampling and an electronic backend for quantization. The photonic frontend includes a photonic sampling pulse generator for directly high-speed sampling and an optical time-division demultiplexer (OTDM) for channel demultiplexing. It is found that the frequency response of the CI-PADC is influenced by both the photonic sampling pulses and the OTDM, of which the combined impact can be characterized through demultiplexed pulse trains. First, the frequency response can be divided into multiple frequency intervals and the range of the frequency interval equals the repetition rate of demultiplexed pulse trains. Second, the analog bandwidth of the CI-PADC is determined by the optical spectral bandwidth of demultiplexed pulse trains which is broadened in the OTDM. Further, the effect of the OTDM is essential for enlarging the analog bandwidth of the CI-PADC employing the photonic sampling pulses with a limited optical spectral bandwidth., Comment: 11 pages, 8 figures

This brief presents a low-power counter-based adaptive equalizer that does not require additional power-hungry comparators for an equalizer adaptation loop. A pulse generator in the proposed equalizer obviates the need for additional error sampling comparators. Instead, it allows the receiver to utilize an output of a data decision comparator for the equalizer adaptation by generating a pulse that indicates whether the comparator makes a firm decision for the incoming data. A single comparator is shared by the data recovery path and equalizer adaptation loop. Consequently, the proposed counter-based equalizer achieves a low power dissipation owing to the reduced number of comparators. Fabricated in a 28-nm CMOS technology, the prototype receiver occupies an active area of 0.004 mm2 and consumes only 0.99-pJ/b at 15-Gb/s.

We present a new approach of the passive microwave pulse compression for gigawatt power generation. Two stages of resonant-cavity-based pulse compressors are cascaded and the peak power gain is multiplied to 12. Candidate passive pulse compressors and cascaded schemes are studied theoretically from the perspective of a linear time-invariant (LTI) system. The compact $S$ -band (2.856 GHz) prototype system consists of six correction cavities and two storage cavities, with the ability to flatten the first-stage pulses and generate the two-stage compressed pulses with exponentially decaying waveforms. It compresses power pulses of 100 MW and $3.6~\mu \text{s}$ generated by commercial klystrons to the peak power of 1.2 GW and full-width at half-maximum (FWHM) pulse durations of 100 ns. The pulse phase is controllable and the power can be combined for either input sources or outputs. This would be attractive to various applications, such as high gradient accelerator and hot dense plasma generation.

Three types of pulses, namely the control, drive, and power pulses, coexist in power electronics systems. The transmission of them embodies the idea to control energy flow with signal flow. However, due to the nonideal performance of the semiconductor switches and the parasitic elements, significant delay and distortion are inevitable during the transmission, causing severe challenges in terms of both device- and system-level performance. Taking silicon carbide (SiC) MOSFET-based system as an example, this article studies the transmission of the three pulses. Time-domain studies are provided first to derive the characteristic parameters of the delay and distortion. Based on the time-domain expressions, a pulse decomposition method is proposed to study the frequency spectrum of the power pulse considering all major transient factors. Experimental results are provided to verify the proposed method and the acquired results. Based on the analyses, the impact of pulse delay and distortion on system performance is summarized, and the general idea of active gate controlling for the power pulse is briefly discussed. This article provides quantitative studies and relevant discussions from the perspective of pulse transmission to improve the analysis, gate-drive design, and active gate control of switching transient.

The linear–nonlinear step load control is proposed to meet the requirements of the pulse load. The nonlinear optimal step control from absolute no-load to full-load is able to force the converter to reach the full-load steady-state operation point with the minimum output voltage drop and minimum settling time. The key is to calculate the initial switching frequency and the duty cycle of the first switching period depending on the load condition. The proposed method is realized by analytic geometry analysis on the state trajectory and confirmed in a 6.6-kW 1-kV/48-V SiC LLC converter. From no-load to full-load, the output voltage drops by 2.24 V and the settling time is 0.76 ms, which reduce by 18.8% and 79.3% compared with the conventional linear control, respectively. Under 100-Hz pulse load with the duty cycle of 30%, the output voltage drop is limited within 2.30 V and overshoot by 1.68 V.

In this article, a new modular structure of Marx generators (MGs) based on interleaved boost converter is proposed. The converter operates in discontinuous conduction mode to generate a high-voltage pulsed power with a common low-voltage source. Unlimited stages can be added to the proposed structure to reach lower maximum voltage stress for the semiconductors or to generate several kilovolts of the output pulses, while the voltage of the semiconductors remains constant. This structure resulted in a higher pulse repetition rate, fewer semiconductor elements, and lower semiconductor voltage stress in comparison to conventional MGs. Hence, the proposed structure is applicable for and efficient in supplying plasma applications with high-voltage pulses. The theoretical foundation of the introduced converter is presented and its performance is simulated using OrCAD software. Based on the obtained results, the maximum voltage of the output pulse is 40 times the input voltage in a single-stage structure. An 80-W prototype of the proposed structure was built to validate the accuracy of the theoretical foundation and the simulation results.

As a kind of high power pulse power supply, the air-core compensated pulse alternator (CPA) is widely used in electromagnetic emission, laser weapon, pulse capacitor charging, and other fields. A brush structure or a brushless structure can be used in the air-core CPA. Because the brushless structure is more suitable for high-speed operation and has higher reliability, more and more scholars have studied the brushless structure air-core CPA. In this article, an electric excitation brushless air-core CPA which the equivalent pole-pairs number is one is proposed. The CPA adopts a brushless rotor winding designed based on the principle of magnetic field differential modulation, which can simultaneously produce two and three pole-pair magnetic fields rotating in the same direction. The rotor winding can couple the field winding and the armature winding at the same time, thus realize electromechanical energy conversion. Under the same conditions, the pulsewidth of pulse discharge current can be significantly increased by reducing the number of pole pairs of the CPA and the output energy of a single pulse can be improved. In this article, a detailed design method of the differential modulation rotor winding of the CPA is presented, and the harmonic content of the CPA is calculated by analytical and numerical methods. Finally, the finite element model is used to analyze the related performance of the CPA, and the analysis results verify the effectiveness of the design scheme.

Spatiotemporal mode-locked (STML) fiber lasers attract great interest owing to their distinctive spatiotemporal characteristics and potential to generate high-energy pulse. Herein, we report an all few-mode fiber figure-eight laser STML by a nonlinear amplifying loop mirror at 1.0 µm. The laser can generate single and multiple pulses at different central wavelengths. In particular, various types of bound-state solitons, such as conventional bound-state solitons and double bound-state solitons, are also achieved and further confirmed by the numerical simulations. The obtained results contribute to further understanding the nonlinear characteristics of STML fiber lasers and such a laser has potential applications in optical communications, especially in information coding.

In this paper, we present a compact memristor model for bipolar neuromorphic ReRAM devices. The proposed model focuses on the high level description of the device, and it reproduces some of the most important characteristics (i.e. conductance, energy dissipation) without needing a detailed electrical simulation. Its functionality is shown by using it to model the behavior of three different ReRAM devices that were fabricated and measured at the CNR-IMM, MDM Laboratory. The parameters extraction procedure is also discussed. The obtained results clearly show that the model proposed in this paper is able to capture the influence of the programming pulse parameters (i.e. pulse duration and height) changes. This is accomplished by the introduction of a parameter, which is related to the specific device technology.

With the technology scaling down, the single event transients produced in the combinational circuit lead to an increasing threat to reliability. In this paper, Dummy Gate Enhanced Charge Sharing (DGECS) technique is proposed to mitigate single event transients, and enhances the pulse quenching of logic cells by increasing the charge sharing between key transistors. Mixed-mode 3-D technology computer aided design simulations were carried out with commercial 65nm dual-well CMOS technology. The simulation results show that the proposed layout technique can significantly reduce single event transient pulse widths and even completely quench transient pulses.

Research is devoted to investigation of properties of pulsed explosive emission cathodes for X-ray tubes. Three types of annular explosive emission cathodes were studied: metal ceramic with slits (of a comb-shaped kind), ring metal ceramic, and carbon ceramic. A pulsed high-voltage generator used in experiments is characterized with the following parameters: voltage pulse full-width at half-maximum is about 20 ns, pulse voltage amplitude is up to 150 kV, and pulse repetition rate is up to 200 Hz. The installation makes it possible to study demountable models of pulsed X-ray tubes of different designs. Current and voltage waveforms corresponding to different operation modes and rates of rise of X-ray tube anode voltage were analyzed. The obtained characteristics of explosive cathodes depend on the cathode’s material, the shape, and the supply voltage of the primary energy storage. The current pulse duration for the ring carbon-ceramic cathode is considerably lower than that for the other cathodes, although it generates a higher radiation dose rate.

Moving the fiber laser emission to the region below one micron may provide a cheaper, more compact and robust alternatives to the existing solid state lasers. Here, for the first time we report a neodymium mode-locked fiber laser emitting at 905 nm in the all-fiber polarization maintaining configuration. We obtain a self-starting pulse generation in nonlinear amplifying loop mirror (NALM) cavity configuration. To suppress a dominant emission at 1064 nm corresponding to a 4-level laser scheme, we use an active fiber - 920/1064 division multiplexer - active fiber sandwich-like sequence in the NALM loop. A rectangular shape dissipative soliton had nJ energy, 30 pm spectral width and 80 - 430 ps width linearly depending on the pump power. Excellent agreement with numerical simulation allowed us to recover pulse shape and width for the pulses out of autocorrelation window., Comment: 7 pages, 4 figures

This article describes the performance of a multi-gap, multichannel (MGMC) spark gap switch, evaluated numerically and experimentally, to achieve multichanneling using a relatively low-magnitude trigger pulse. First, an electrostatic analysis of the switch geometry was carried out using COMSOL Multiphysics 5.5 to determine the electric field distribution during high-voltage hold-off before triggering and to determine the coupling parameters between trigger and other intermediate electrodes of the switch. Second, a circuit model was developed in PSpice Lite 16.6 for predicting the process of channel formation and its influence on adjacent channels. Based on the simulation results obtained, a six-gap, eight-channel, planar MGMC switch operating in air has been designed and developed. The developed switch was, then, incorporated into a compact experimental setup to experimentally evaluate various switch parameters such as inductance, switching delay, jitter, and closing time when triggered using a negative-polarity trigger pulse of magnitude −40 kV, generated using a compact, in-house developed trigger generator. In contrast to most of the reported MGMC switches that use complicated Marx-based generators to produce ≥120-kV trigger pulses for multichannel formation, the experimental results, thus obtained, report comparable switch performance using a low-magnitude (−40 kV) trigger pulse. In addition, framing and streak camera images taken during the current discharge indicate the presence of ~6 luminous channels. In addition, short-circuit experiments for estimating switch inductance by consecutively shorting one or more channels also indicate multichanneling in the switch using a low-magnitude trigger pulse.

Optical systems typically use galvanometers (galvos) and scanners. Galvos move, quasi-statically, from one static position to another. Scanners move in an oscillatory fashion, typically at the device resonant frequency. MEMS devices, which have many advantages and are often used in optical systems, are typically high Q devices. Moving from one position to another for a galvo or one amplitude to another for scanners, can take many periods to settle following the ring down. During these transitions, the optical system is inactive. Here, we show how precisely timed pulses can be used (in an open loop manner) to begin or end scanner motion without ring up/ring down time. The size of pulse required is found to depend on the Q of the device, and relationships are derived. The pulse can also be separated into multiple pulse spaced one period apart if pulses of the necessary size are not possible due to constraints of the physical device. For finite Q scanners, the amplitude decreases after the initial pulse due to damping. This can be eliminated by applying an excitation at the frequency of the scanner. The necessary amplitude for this excitation is derived. Finally, by combining this open loop control algorithm with an open loop control algorithm for galvo motion the device can seamlessly move between scanner and galvo functioning. These control algorithms are demonstrated using computer simulations, analytical models and a commercially available MEMS mirror (Mirrorcle Technologies, A8L2.2). [2020-0238]

We developed a fabrication process to establish large arrays of up to 5-stacked Josephson junctions for the Josephson Arbitrary Waveform Synthesizer (JAWS). SNS-type Josephson junctions with NbxSi1-x barriers are used for this application. By modifying our standard window process, e.g. to add a CMP (chemical mechanical polishing) and an ALD (atomic layer deposition) step, the yield of this process was increased. An output voltage of 1 V RMS could be achieved by using 4 JAWS arrays in series with a total number of 60,000 5-stacked junctions. The investigation of the current-voltage characteristics (IVC) showed an interesting and potentially useful feature. The required pulse amplitude per junction for getting the maximum Shapiro step width reduces for higher junction stacks. We found that the pulse power linearly reduces with the square of the junction number in the array. The origin of this effect might be a strong neighbour-neighbour interaction of the junctions, which are closely arranged within the stacked configuration. This might generate a strong self-synchronization of the junctions.

In order to eliminate the noise on the pulse interval of high-speed spike-based image sensor, a pulse interval compensation (PIC) algorithm is proposed. Based on the analysis of the principle of sensor noise generation, a pulse interval error model is constructed and the compensation algorithm is developed. First, raw pulse data is obtained from the sensor system, and then the coefficient matrix is used to compensate the non-uniform pulse interval caused by the dark current. Then, the guided filter separates high-frequency noise from scenes details and the pulse interval compensation matrix is obtained in the corresponding pulse interval. Finally, the pulse interval compensation is performed on the raw pulse data for correction. In static scene experiments, the proposed method is compared with the existing state-of-the-art methods and shows a clear advantage in denoising in both low texture and rich texture scenes. In the experiment to film a turntable at a rotation speed of 2000 r/min, 3000 r/min, 6000 r/min, the average roughness decreases from 0.2830 to 0.2034, 0.2937 to 0.2139 and 0.3252 to 0.2501 respectively. These experiments proved that the proposed method can effectively eliminate the noise of the spike-based image sensor.

In laser acceleration of ions by the radiation pressure acceleration (RPA) mechanism, the efficiency of energy and momentum transfer to ions increases if the shape of the laser pulse is suitably tailored. Numerical results are presented for the Gaussian, Lorentzian, and hyperbolic secant pulse shapes of the incident laser interacting with an ultrathin, ultra-dense plasma foil. The numerical results show that the energy and momentum imparted to the ions by the hyperbolic laser pulse are 1.17 and 1.11 times more compared to the Lorentzian shaped pulse of approximately the same intensity.

This brief presents an on-off keying (OOK) driven impulse radio ultra-wideband (IR-UWB) pulse generator (PG) for 3–5 GHz applications, featuring high sidelobe suppression (SLS), large bandwidth ( $BW_{-10dB}$ ), and robustness against process variations. To eliminate the need for a dedicated off-chip pulse-shaping filter, a transistor-sizing-based pulse shaping scheme is adopted to generate a broadband pulse with a triangular envelope, ensuring enhanced SLS with extended signal bandwidth. The proposed process compensating circuit mitigates the effects of process variations on the propagation delay of the logic gates to provide stable pulse timing characteristics. Implemented in 65-nm CMOS process, the prototype PG provides a UWB pulse with an amplitude of 634 ${\mathrm {mV}}_{pp}$ , $BW_{-10dB}$ of 1.12 GHz, and 27 dB SLS, while occupying a total chip area of 964 $\mu \text{m}\,\,\times $ 669 $\mu \text{m}$ . The proposed PG provides enhanced pulse characteristics with modest energy consumption among the reported works. Based on the proposed figure-of-merit considering the SLS and quality of pulse, the PG in this work shows a competitive FOM of $3.36\times 10^{9}$ .

A highly inclusive theory of Q-switched lasers is presented which applies to both actively and passively Q-switched lasers. The theory expands on the author’s previous publications on energy optimization to include: (1) saturable absorbers exhibiting excited state absorption and therefore a finite Figure of Merit (FOM); (2) unequal beam areas in the gain and absorbing media; and (3) both pulsed and CW pumping. Design curves for optimizing the output energy for pulse pumped lasers and CW pumped lasers at a desired pulse rate are provided. As in the author’s previous work, the optimization equation is obtained utilizing Lagrange Multipliers and yields the value of the parameter $\rho = ln(n_{i}/n_{f})$ which maximizes the single pulse energy, where $n_{i}$ and $n_{f}$ are the laser inversion population densities before and after Q-switching. Using this initial result, the associated optimum absorber transmission and mirror reflectivity, pulse energy, peak power, and pulse width can be computed sequentially via simple formulas. The aforementioned parameters can all be expressed as functions of two variables, $\alpha $ and $z_{eff}$ , which are slight modifications of the variables $\alpha $ and z previously introduced by the author for passively Q-switched lasers having infinite FOM and equal beam areas The term “plane wave theory” has sometimes been used by this and other authors in prior publications to describe a uniform pump profile in the laser medium, but we will refer to this special case more accurately as the “uniform pump theory”. The theory is extended here in the final section to include non-uniform pumping. The common case of a Q-switched laser end-pumped by a quasi-Gaussian CW laser is considered in detail and the theoretical results are found to agree well with experimental data.

J-PARC E16 is an experiment to examine the origin of hadron mass through a systematic measurement of spectral changes of vector mesons in nuclei. The measurement of $e^{+}e^{-}$ pairs from the decay of vector mesons will provide the information of the partial restoration of the chiral symmetry in a normal nuclear density. To resolve a pulse pile-up and achieve good discrimination of $e^{+}$ and $e^{-}$ from the background of a reaction rate of an order of 10 MHz, the data acquisition (DAQ) system uses waveform sampling chips of APV25 and DRS4. The trigger rate and data rate are expected to be 1 kHz and 120–330 MiB/s, respectively. The DAQ system for readout of APV25 and DRS4 were developed, where events were synchronized by common trigger and tag data. The first commissioning in beam, called Run-0a, was performed in June 2020 with about 1/4 of the designed setup. The DAQ worked with a trigger rate of 300 Hz in the Run-0a and the main bottleneck was a large data size of APV25. Further optimization of the DAQ system will improve the performance.

The nanosecond short pulse generator, which operates continuously at MHz repetition rates, plays an important role in high-energy accelerators, pulsed laser modulation, electromagnetic biological effects, and other fields. Pulse-forming lines based on gas spark gap are the main means to generate high-voltage nanosecond short pulses; but due to electrode ablation, it is difficult to operate at MHz repetition rates. The topologies based on the fully controlled semiconductor device can output multimode nanosecond pulse. But it is limited by the gate driver ability and system stray loss, so it is difficult to directly generate flexible and adjustable nanosecond short pulse with MHz repetition rates. In order to overcome the above shortcomings, this article proposes the Blumlein-based LC underdamped oscillation boost circuit and the Blumlein stack topology to achieve high voltage gain. And, the voltage wave process can be adjusted by controlling the switching sequence to change operating mode. Finally, multimode operation such as positive polarity, negative polarity, bipolar and pulse duration modulation can be realized with MHz repetition rates and high gain voltage.