Auxiliary Pulse Research Articles

Vibrational squeezing via spin inversion pulses

Magnetic resonance force microscopy (MRFM) describes a range of approaches to detect nuclear spins with mechanical sensors. MRFM has the potential to enable magnetic resonance imaging with near-atomic spatial resolution, opening up exciting possibilities in solid state and biological research. In many cases, the spin-mechanics coupling in MRFM is engineered with the help of periodic radio frequency pulses. In this paper, we report that such pulses can result in unwanted parametric amplification of the mechanical vibrations, causing misinterpretation of the measured signal. We show how the parametric effect can be canceled by auxiliary radio frequency pulses or by appropriate post-correction after careful calibration. Future MRFM measurements may even make use of the parametric amplification to reduce the impact of amplifier noise.

Study on temperature field in the process of induction heat treatment with current assisted weld double side method

At present, in the process of weld induction heat treatment, the common method is to carry out centralized induction heating in the weld area, which will lead to large radial temperature difference of the weld, poor controllability of temperature distribution and easy to cause the defects of residual stress concentration in the weld area. To solve the above problems, this paper adopts the two-sided method to conduct induction heating on both sides of the weld, and at the same time, the auxiliary pulse current is passed into the weld to improve the quality of the weld. ANSYS finite element software is used to establish a multi-field coupling prediction model of electric-magnetic-thermal structure, and explore the distribution law of the auxiliary pulse current and the temperature field of the weld. Finally, an experimental study of pulsed current assisted two-sided induction heating is carried out. Temperature test and metallographic test were carried out respectively to verify the effectiveness of pulsed current assisted induction heating technology.

Study on pulse current auxiliary heating process of submerged arc welding

During the welding process, temperature filed distribution of weldment is one of the key factors which influence welding quality. In order to improve the mechanical properties of welding joint, a technology for heating process of weldment using auxiliary pulse current was proposed in this article. Firstly, through metallographic experiment, strength experiment and hardness experiment, it was proved that the auxiliary pulse current not only can refine grain size but also improves the mechanical property of the welding joint. Then the paper used ANSYS and its ANSYS Parametric Design Language parametric design language to simulate the welding process with assistant pulse current, and the temperature field, the pulse current density distribution and the time of effective pulse current in the welded joint were obtained. Quantitative analyses were undertaken on the influence laws of auxiliary pulse current parameters on weld temperature field, auxiliary pulse current density distribution and the time of effective pulse current. A new parameter was defined as time-current density (the time integral of current density) to demonstrate the change rule of auxiliary pulse current density distribution with time. Finally, analyzing the reasons for raising the welding quality. There were two reasons for such phenomenon: one was auxiliary pulse current change the state of heat distribution in the weld seam area, the other was that the impulse oscillation of the auxiliary pulse influences the nucleation process of melting region.

Local enhancement in transient absorption spectroscopy by gating the resonance in the time domain

The concept of resonant perfect absorption, enabled by the combined action of pulse propagation and an auxiliary gate pulse, was recently proposed and demonstrated in a group of two-level systems [Y. He , ]. Here we exploit this method in a more realistic scenario by solving the coupled time-dependent Schrödinger equation and the Maxwell wave equation in helium. Through emptying the population of the 1s2p excited state after its excitation, we explore the evolution of the spectral profile with time delay and propagation distance and link the observations to the controlled interference between the original field and the gated new field. We find that resonant absorption for higher-lying states can also be strongly enhanced, in spite of the congestion of multiple resonances and the presence of complex laser-induced couplings. Our results show that interferometric control of absorption using intense laser fields can be applied selectively in both the temporal and spatial domains. Published by the American Physical Society 2024

Ion trap and release dynamics enables nonintrusive tactile augmentation in monolithic sensory neuron.

An iontronic-based artificial tactile nerve is a promising technology for emulating the tactile recognition and learning of human skin with low power consumption. However, its weak tactile memory and complex integration structure remain challenging. We present an ion trap and release dynamics (iTRD)-driven, neuro-inspired monolithic artificial tactile neuron (NeuroMAT) that can achieve tactile perception and memory consolidation in a single device. Through the tactile-driven release of ions initially trapped within iTRD-iongel, NeuroMAT only generates nonintrusive synaptic memory signals when mechanical stress is applied under voltage stimulation. The induced tactile memory is augmented by auxiliary voltage pulses independent of tactile sensing signals. We integrate NeuroMAT with an anthropomorphic robotic hand system to imitate memory-based human motion; the robust tactile memory of NeuroMAT enables the hand to consistently perform reliable gripping motion.

Self-consistent soliton evolution in single-two-mode fiber lasers.

Ultrafast few-mode fiber lasers have received increasing attention from basic research to practical applications due to their unique pulse performance and intriguing nonlinear dynamics. Here, we experimentally and numerically reveal the formation and evolution behaviors of a soliton in a mode-locked fiber laser composed of two-mode and single-mode fibers. The LP11 pulse walks away from the LP01 pulse in the two-mode fiber due to modal dispersion and then transforms into an auxiliary LP01 pulse after entering the single-mode fiber. After re-entering the two-mode fiber, the LP01 pulse excites the LP11 pulse via mode coupling; therefore, the LP11 pulse also consists of dominant and auxiliary pulses. Such a soliton fiber laser converges to an asymptotic steady state with unlocked spatial modes arising from the interplay between the strong modal dispersion and weak mode coupling.

Collimated particle acceleration by vortex laser-induced self-structured “plasma lens”

A micrometer-scale “plasma lens” self-constructed by the prepulse and main pulse of the Laguerre–Gaussian (LG) laser is realized to enhance the collimation and acceleration of proton beams in a target normal sheath field acceleration mechanism. Hydrodynamic FLASH and particle-in-cell simulations are carried out and find that a collimated proton source with beam divergence ∼2.7° is generated by the LG laser, which is smaller than the case driven by the traditional Gaussian laser. It demonstrates that the curved sheath field on the “plasma lens” plays an important role in the beam collimation. Such an approach considerably relaxes the constraints of complex design for the target fabrication and auxiliary laser pulse, opening new doors for high-repetition-rate collimated proton accelerations for innovative applications in upcoming high-repetition-rate petawatt laser systems.

Free‐Electron Tomography of Few‐Cycle Optical Waveforms

AbstractUltrashort light pulses are ubiquitous in modern research but the electromagnetic field of the optical cycles is usually not easy to obtain as a function of time. Field‐resolved pulse characterization requires either a nonlinear‐optical process or auxiliary sampling pulses that are shorter than the waveform under investigation and pulse metrology without at least one of these two prerequisites is often thought to be impossible. Here is reported how the optical field cycles of laser pulses can be characterized with field‐linear sensitivity and no ultrashort probe events. A free‐space electron beam is let to cross with the waveform of interest. Randomly arriving electrons interact by means of their elementary charge with the optical waveform in a linear‐optical way and reveal the optical cycles as the turning points in a time‐integrated deflection histogram. The sensitivity is only limited by the electron‐beam emittance and can reach the level of thermal radiation and vacuum fluctuations. Besides overturning a common belief in optical pulse metrology, the idea also provides practical perspectives for in situ characterization and optimization of optical waveforms in higher‐harmonics experiments, ultrafast transmission electron microscopes, laser‐driven particle accelerators, free‐electron lasers, or generally any experiments with waveform‐controlled laser pulses in a vacuum environment.

Effect of spontaneous emission on the shortcut to adiabaticity in three-state systems

The shortcut to adiabaticity (STA) is a powerful technique to speed up population transfer via quantum coherent control. This paper demonstrates that STA provides a fast, robust, and efficient population transfer compared to the stimulated Raman adiabatic passage. In the ideal situation of a closed system, STA is insensitive to the detunings and Rabi frequencies, and the undesired diabatic transitions could be eliminated by the auxiliary pulses, so the complete population transfer from the initial state to the target state in the designed adiabatic passage can be rapidly achieved against the inevitable amplitude noises of the interactions and systematic errors. When we consider the situation including the environment noises, spontaneous emission from the intermediate state $|2\ensuremath{\rangle}$ in STA can be sufficiently ignored in the cases of the dark-state evolution and quantum overdamping, since the state $|2\ensuremath{\rangle}$ is thoroughly separated from the three-state system. Moreover, the diabatic transitions induced by the spontaneous emission are also sufficiently suppressed in STA.

Actively tunable photonic crystal-based switch via plasmon-analog of index enhancement

We propose a miniaturized photonic switch, which utilizes (recently discovered) plasmon analog of index enhancement. An index is tuned via a control (auxiliary) pulse. The operation principle of the proposed device, composed of a few layers of nanorod dimers, is different than the conventional photonic switches. In the proposed device, a stop band is created at the desired frequency determined by the control pulse frequency. Calculated modulation depths are quite large, and response time is determined by the plasmon lifetime. The method we propose here is based on linear operation that requires low power and has very small foot-print that satisfies the major needs to be the choice of a switching scheme for integrated optics.

Laser-driven collisionless shock acceleration of protons from gas jets tailored by one or two nanosecond beams

It was proposed recently that laser-ion acceleration in gas jets may be significantly improved if each side of a gas jet target is tailored by an auxiliary nanosecond laser pulse [Marquès et al., Phys. Plasmas 28, 023103 (2021)]. In the present study, the proton acceleration by electrostatic shock in these one- or two-side tailored plasmas is investigated using particle-in-cell simulations. It is demonstrated that the formation of a thin plasma layer with a steep density profile and a maximum density of the order of the critical density strongly improves the proton acceleration in the forward direction with a maximum ion energy of tens of MeV with mildly relativistic laser pulses. Proton acceleration up to tens of MeV is predicted using realistic plasma density profiles obtained from tailored gas jet targets compared to a few MeV reported in other publications.

Optically Switchable MeV Ion/Electron Accelerator

The versatility of laser accelerators in generating particle beams of various types is often promoted as a key applicative advantage. These multiple types of particles, however, are generated on vastly different irradiation setups, so that switching from one type to another involves substantial mechanical changes. In this letter, we report on a laser-based accelerator that generates beams of either multi-MeV electrons or ions from the same thin-foil irradiation setup. Switching from generation of ions to electrons is achieved by introducing an auxiliary laser pulse, which pre-explodes the foil tens of ns before irradiation by the main pulse. We present an experimental characterization of the emitted beams in terms of energy, charge, divergence, and repeatability, and conclude with several examples of prospective applications for industry and research.

Analysis of the Influence of Diesel Spray Injection on the Ignition and Soot Formation in Multiple Injection Strategy

Multiple injection strategies have increased their capabilities along with the evolution of injection system technologies up to the point that nowadays it is possible to inject eight different pulses, permitting to improve the engine performance, and consequently, emissions. The present work was realized for two simplified strategies: a pilot-main and a main-post, in order to analyze the influence of an auxiliary pulse on the main and otherwise, in reactive conditions for two pilot/post quantities and four hydraulic dwell times. The study was carried out by employing two optical techniques: diffused back-illumination with flame bandpass chemiluminescence for measuring soot, represented by soot-maps distribution, and single-pass schlieren for ignition delay (ID). Furthermore, a novel methodology for decoupling the start of combustion (SOC) of the second pulse was developed and successfully validated. From the ignition delay results, it was found for all test points that the pilot injection enhanced conditions, which promote a faster ignition of the main pulse, also at higher chamber temperatures, all conditions presented a separate combustion event for each injection. In emission terms, soot increased in the pilot-main strategies compared to its single injection case, as well as, in conditions that promote faster-premixed combustion.

Interfacial structure and joint strength on Ti(C, N)–Al2O3 cermet/40Cr steel joints with diffusion bonding

The [Formula: see text]–[Formula: see text] cermet to 40Cr steel joint was conducted by liquid phase diffusion bonding under the auxiliary pulse current and using 73Cu–27Ti amorphous foil/Cu foil/72Ag–28Cu foil sandwich foils as the interlayer. The effect of holding time and duty ratio of the pulse current on interfacial structure at the [Formula: see text]–[Formula: see text] cermet side and joint strength were studied. The results showed that the longer bonding time can improve the melting of Cu–Ti foil and the dissolution of Cu interlayer to obtain a higher joint strength. The interfacial structure was composed of the TiCu compounds and Cu solid solution at the cermet side, and [Formula: see text] compounds and Cu solid solution at the Cu interlayer side. The auxiliary pulse current was beneficial to reach a higher joint strength in a shorter holding time. A higher duty ratio would accelerate the dissolution and reaction of cermet to the interlayer, but continuous increase on the duty ratio would result in the over dissolution of cermet into the interface to produce the Ti(C, N) and [Formula: see text] ceramic particles and the decrease on the joint strength.

Fast preparing W state via a chosen path shortcut in circuit QED

We present a scheme of choosing a dressed state as an evolutive path to prepare three-superconducting qubit (SQ) W state. In the circuit quantum electrodynamics, there are three SQs trapped, respectively, in three coplanar waveguide resonators, which are coupled to a superconducting coupler qubit. With the help of quantum Zeno dynamics, we get the effective Hamiltonian of the system. Our strategy is adding two auxiliary pulses to the effective Hamiltonian. New driving pulses can cancel non-adiabatic transitions, so the whole system will evolve exactly along the chosen path. By setting boundary conditions, the W state can be obtained in a short time. Furthermore, in the chosen evolutive path state, the intermediate state’s population can be restricted by setting appropriate parameters, which is very useful for resisting the effects of dissipation. Numerical simulations indicate that the proposed scheme is robust against spontaneous emissions, dephasing, the cavity photon leakage and the parameter fluctuations.

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.

Reconstruction of coherent anti‐Stokes Raman scattering signals generated by means of laser pulses with asymmetric amplitude and phase

AbstractTime and frequency asymmetries in ultrashort chirped laser fields might appear as a consequence of dispersive propagation, pulse shaping techniques, or generation of auxiliary light pulses needed in nonlinear optics. Here, we try to find an answer to the question of how to solve analytically coherent anti‐Stokes Raman scattering (CARS) under asymmetric conditions of chirped femtosecond laser pulses. The approach breaks in two parts. One for the field amplitudes and the other for the phases. The former revolves around Gaussian dependences that, besides being rather common in ultrashort laser physics, can be arranged and mixed to reproduce spectrally asymmetric laser amplitudes. The latter is limited to field phases with cubic frequency dependence (i.e., second‐order chirp) whose asymmetry is simulated by adding a linear term to the quadratic phase. Both approximations for amplitudes and phases of the three laser pulses are mandatory to guarantee the solution to the complexity posed by the CARS problem. Comparisons with known experimental and numerical results support the validity of the model.

Analysis of transient-absorption pump-probe signals of nonadiabatic dissipative systems: "Ideal" and "real" spectra.

We introduce and analyze the concept of the "ideal" time and frequency resolved transient-absorption pump-probe (PP) signal. The ideal signal provides the most direct link between the "real" (measurable) PP signal and the material system dynamics. The simulation of PP signals involves two steps. (i) The ideal signal, which exhibits perfect time and frequency resolution, is calculated. For this purpose, the probe pulse is replaced by an auxiliary continuous-wave pulse. (ii) The real signal is obtained by the convolution of the ideal signal with the appropriate time- and frequency-gate function, which depends on the envelope of the actual probe pulse. This concept has been used to simulate integral and dispersed PP signals for a model system exhibiting nonadiabatic and dissipative dynamics. The ideal signal is computed with the two-pulse equation-of-motion phase-matching approach which has been extended to take excited-state absorption into account. We demonstrate how the ideal signal, an object exhibiting the features of moving wave packets as well as stationary spectra, is related to real signals detected with short (good temporal resolution) or long (good frequency resolution) probe pulses.

AUXIN PULSE IN THE INDUCTION OF SOMATIC EMBRYOS OF Eucalyptus

ABSTRACT The objective of this study was to evaluate the effect of auxin pulse intervals on the induction of somatic embryos of Eucalyptus grandis x E. urophylla and to describe the embryogenic behavior of callus under the effect of auxinic stress. Cotyledons were inoculated in culture medium containing 207.07 µM picloram, a treatment considered as auxin pulse. Explants that were in the auxin pulse treatment were transferred to semisolid or liquid medium containing 20.71 µM picloram after one, two, four or eight days of auxin pulse. In a second experiment, explants that were on auxin pulse treatment were transferred to semi-solid medium containing 20.71 µM picloram after one, two or three days of auxin pulse. Auxiliary picloram pulse treatments (207.02 µM) can be used as an initial source of stress for the acquisition of embryogenic competence. The oxidation of cotyledonary explants may be considered as an indication of the formation of embryogenic calli. The presence of pectins in peripheral regions of somatic pro-embryos can be considered as a marker of somatic embryogenesis in cotyledonary explants of Eucalyptus grandis x E. urophylla.

Experimental Extraction of the Charge Centroid of Holes Trapped in Metal–Oxide–Nitride–Oxide–Semiconductor Memories

In metal-oxide-nitride-oxide-silicon (MONOS)-type memories with an ultrathin tunnel oxide film, electrons and holes are injected from the silicon substrate to the silicon nitride charge trapping film owing to the quantum mechanical tunneling and are trapped in the film. In the previous studies, the constant-voltage carrier injection method has been used to determine the charge centroid of trapped carriers [1-4]. This method requires the application of an auxiliary pulse before injecting carriers. To determine the auxiliary pulse level, another set of measurements of the programming and erasing characteristics is needed in preliminary step. Such a sequence would generate an error in the charge centroid estimation due to the variation of the programming and erasing characteristics among individual memory elements. Therefore, we have developed the constant-current carrier injection (CCCI) method which does not require the application of the auxiliary pulse and any additional measurements [5]. The CCCI method is effective to obtain the accurate charge centroid of trapped carriers. On the other hand, these two methods can be used only in the case that the number of carriers passing through the silicon nitride film during the carrier injection is negligible as compared to that of carriers trapped in the nitride film. Therefore, neither of the two methods is usable with high gate voltages which induce a large number of carriers passing through the nitride film. In the present work, in order to obtain the charge centroid of holes trapped in the silicon nitride film at high gate voltages, we proposed a method based on the analysis of Fowler-Nordheim (F-N) tunneling current through the blocking oxide film. We determined the charge centroid and the density of holes trapped at high gate voltages by means of the proposed method and the CCCI method. Memory capacitors with the blocking oxide (SiOx)/silicon nitride/tunnel oxide stacked films were used in this work. A tunnel oxide film of 2.4 nm in thickness was grown by rapid thermal oxidation of silicon. A 30.4-nm-thick silicon nitride film was deposited at 600 °C in an LPCVD reactor. A blocking oxide film of 17.2 nm in thickness was grown at 400 °C using a PECVD method. The thickness of the blocking oxide film was designed to be sufficiently thick for electrons to obey the F-N tunneling mechanism and to gain a high kinetic energy in the oxide film. High-energy electrons entering the nitride film from the blocking oxide film would pass through the nitride film without interaction with nitride trap centers. Figure 1 shows the charge centroid of holes trapped in the nitride film, which was obtained by means of the analysis of F-N current under negative gate bias and the CCCI method. The charge centroid of trapped holes was initially located near the middle of the nitride film, and moved toward the blocking oxide-nitride interface as the flat-band voltage shift ΔVfb,h increased. Finally, the charge centroid reached 2.3 nm from the blocking oxide-nitride interface after the ΔVfb,h value was saturated. We also have estimated the density of trapped holes. A maximum of the density of trapped holes was determined to be 1.0×1013 holes/cm2 by means of the analysis of F-N tunneling current. The proposed method is useful to determine the maximum density of trapped holes which the charge trapping film in MONOS-type memories can achieve. Acknowledgment- We would like to express gratitude to S. R. A. Ahmed, K. Kato and H. Koizumi for their valuable discussions. This work was partly supported by JSPS KAKENHI Grant Number 26420280.