Driver Pulse Research Articles

Tunable UV ∼ IR frequency comb generation via high-order sideband generation

We propose the generation of a widely tunable UV-to-IR frequency comb by high-order sideband generation (HSB) spectrum emitted from semiconductors. In our theoretical simulations, we demonstrate the high-order sideband signals of two series (2m Ωseed + (2n + 1) ωdriver, and (2m + 1) Ωseed + 2 nωdriver ), where m and n are integers of a seed pulse and a driver laser frequency, respectively. The simulations also reveal the intensity of HSB scale with the driver laser power, both perturbatively and non-perturbatively. We find that the harmonic position and spacing of the high-order sideband emission can be controlled by varying the seed pulse and driver photon energies. In the experiment, we applied a visible ( ℏΩseed = 3.1 eV, ∼400 nm) seed pulse and mid-infrared (MIR, ℏωdriver = 0.4 eV, 3.1 μm) driver pulses to ZnSe target. Our experimental observations confirmed the UV (4.7 eV, 263 nm and 3.9 eV, 317 nm) HSB generation.

Dephasingless plasma wakefield photon acceleration.

Sandberg and Thomas [Phys. Rev. Lett. 130, 085001 (2023)0031-900710.1103/PhysRevLett.130.085001] proposed a scheme to generate ultrashort, high-energy pulses of XUV photons though dephasingless photon acceleration in a beam-driven plasma wakefield. An ultrashort laser pulse is placed in the plasma wake behind a relativistic electron bunch such that it experiences a comoving negative density gradient and therefore shifts up in frequency. Using a tapered density profile provides phase-matching between driver and witness pulses. In this paper, we give the details of the wakefield solutions and phase-matching conditions used to generate the phase-matching density profile. The short, high-density, and weak driver limits are considered. We show, explicitly, the numerical algorithm used to calculate the density profiles.

Sub-20 fs, 80 W, up to 2 mJ Yb-based laser multi-pass-cell post-compression: Experimental and numerical results

We report here on the experimental pulse duration compression down to sub-20fs of up to 2mJ, 330fs pulses of an 80W Ytterbium laser, using argon-filled multi-pass-cell reproduced by numerical calculations stressing the role of the driver pulse profile.

Lattice Boltzmann method for warm fluid simulations of plasma wakefield acceleration

A comprehensive characterization of lattice Boltzmann (LB) schemes to perform warm fluid numerical simulations of particle wakefield acceleration (PWFA) processes is discussed in this paper. The LB schemes we develop hinge on the moment matching procedure, allowing the fluid description of a warm relativistic plasma wake generated by a driver pulse propagating in a neutral plasma. We focus on fluid models equations resulting from two popular closure assumptions of the relativistic kinetic equations, i.e., the local equilibrium and the warm plasma closure assumptions. The developed LB schemes can, thus, be used to disclose insights on the quantitative differences between the two closure approaches in the dynamics of PWFA processes. Comparisons between the proposed schemes and available analytical results are extensively addressed.

Experimental and numerical demonstration of driver pulse spectral width and phase dependence in near-single-cycle pulse post-compression generation

For many years, light-matter interaction in the strong-field regime has benefited from continuous improvement of femtosecond lasers, in terms of peak power or repetition rate. One of the most current major challenges is the achievement of high-energy, near single-cycle pulses. Such performances are of primary interest in attosecond science for producing intense isolated bursts of extreme ultraviolet light through high-harmonic generation in gases or solids. We present here a detailed experimental and numerical study on a helium filled hollow-core fiber-based post-compression stage. Our measurements highlight the importance of the width and phase of the input spectrum on the spectral broadening, and on the resulting post-compressed pulse. Near Fourier-transform-limited pulses as short as 3.5 fs, carrying a 2.5 mJ energy centered at 750 nm at 1 kHz repetition rate, and leading to a compression factor greater than seven, are demonstrated. The numerical results are in good agreement with the experimental data. Here, spectral broadening is governed by the Kerr effect and the self-steepening on the trailing edge of the guided pulse.

Electron-beam-driven plasma wakefield acceleration of photons

The paper [R .T. Sandberg and A. G. R. Thomas, Phys. Rev. Lett. 130, 085001 (2023)] proposed a scheme to generate ultrashort, high energy pulses of XUV photons through dephasingless photon acceleration in a beam-driven plasma wakefield. An ultrashort laser pulse is placed in the plasma wake behind a relativistic electron bunch so that it experiences a density gradient and therefore shifts up in frequency. Using a tapered density profile provides phase-matching between the driver and witness pulses. In this paper, we study via particle-in-cell simulation the limits, practical realization, and 3D considerations for beam-driven photon acceleration using the tapered plasma density profile. We study increased efficiency by the use of a chirped drive pulse, establishing the necessity of the density profile shape we derived as opposed to a simple linear ramp, but also demonstrating that a piecewise representation of the profile—as could be experimentally achieved by a series of gas cells—is adequate for achieving phase matching. Scalings to even higher frequency shifts are given.

A novel hybrid discontinuous PWM algorithm for 3L-NPC inverter

Wider linear modulation range, less switching loss and simplicity are the goals pursued by various modulation methods of multilevel inverters. This paper proposes a new hybrid discontinuous pulse width modulation (HDPWM) strategy for 3L-NPC inverter that can achieve the above goals to a certain extent. According to the position of the reference voltage vector and the actual situation of the neutral point voltage, different control modes and clamping types are selected. The neutral point voltage is controlled by DPWM strategy, which cannot only greatly reduce the switch loss, but also maintain the balance of the neutral point voltage and expand the linear modulation range. The implementation of the algorithm combines the advantages of carrier-based PWM (CBPWM) and space vector PWM (SVPWM). There is no need to select the nearest three vectors (NTV) and calculate their dwell time. Only the reference voltage needs to be modified according to the control requirements, and then by comparing the modified reference voltage with the carrier, the driver pulse required by the switching devices can be generated. Compared with the existing PWM methods, it is more simple and easy to implement. Experimental results verify the validity of the method.

Parametric amplification as a single-shot time-resolved off-harmonic probe for laser–matter interactions

Abstract An optical probing of laser–plasma interactions can provide time-resolved measurements of plasma density; however, single-shot and multi-frame probing capabilities generally rely on complex setups with limited flexibility. We have demonstrated a new method for temporal resolution of the rapid dynamics ( $\sim 170$ fs) of plasma evolution within a single laser shot based on the generation of several consecutive probe pulses from a single beta barium borate-based optical parametric amplifier using a fraction of the driver pulse with the possibility to adjust the central wavelengths and delays of particular pulses by optical delay lines. The flexibility and scalability of the proposed experimental technique are presented and discussed.

Single-Cycle, Multigigawatt Carrier–Envelope-Phase-Tailored Near-to-Mid-Infrared Driver for Strong-Field Nonlinear Optics

A short-pulse, frequency-tunable idler-wave output of a two-stage optical parametric amplifier is compressed in a gas-filled antiresonance-guiding hollow-core photonic-crystal fiber to yield ultrashort field waveforms of near-to-mid-infrared (near-IR/mid-IR) radiation with a pulse energy of up to 28 μJ, a peak power of up to 4 GW, and a pulse width smoothly tunable, via gas-pressure adjustment inside the gas-filled hollow fiber, all the way down to a single field cycle at ≤6.6 fs. With the active carrier–envelope phase (CEP) stabilization extended to its entire multioctave bandwidth, the single-cycle near-to-mid-IR fiber output is CEP-stable within 140 mrad and can be finely tailored toward a desired CEP profile. High-order harmonics generated by such pulses in solids exhibit clear signatures of strong-field single-cycle nonlinear optics. Well-resolved harmonic peaks, which dominate the visible–ultraviolet spectrum of the nonlinear-optical response of a solid driven by multicycle near-to-mid-IR pulses, tend to broaden and merge together as the driver pulse width approaches the field cycle, eventually giving rise to visible–ultraviolet supercontinua as a signature of single-cycle light–matter interactions.

High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate

We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation (SHHG) on plasma mirrors at a kilohertz repetition rate, emitted simultaneously with energetic electrons. SHHG spectra and electron angular distributions are measured as a function of the experimentally controlled plasma density gradient scale length L g for three increasingly short and intense driving pulses: 24 fs and a 0 = 1.1 , 8 fs and a 0 = 1.6 , and finally 4 fs and a 0 ≈ 2.1 , where a 0 is the peak vector potential normalized by m e c / e with the elementary charge e , the electron rest mass m e , and the vacuum light velocity c . For all driver pulses, we observe correlated relativistic SHHG and electron emission in the range L g ∈ λ / 20 , λ / 4 , with an optimum gradient scale length of L g ≈ λ / 10 . This universal optimal L g -range is rationalized by deriving a direct intensity-independent link between the scale length L g and an effective similarity parameter for relativistic laser-plasma interactions.

On the electromagnetic-electron rings originating from the interaction of high-power short-pulse laser and underdense plasma

We investigate the evolution of radial profile of a high-power short-pulse laser interacting with underdense plasma, and in particular, we concentrate on the transverse electromagnetic rings, which are formed due to the laser radiation defocusing induced by the excitation of Langmuir waves. We illustrate the physical processes involved in the formation of such structures analytically and use the three-dimensional numerical simulations to reveal the relationships among the electromagnetic ring properties and the parameters of laser and plasma. Within the studied parameter range, we find that up to ≈70 % of the total initial driver pulse energy can be carried off by the electromagnetic rings having the opening angles ≈45–115 mrad. Furthermore, we show that the electromagnetic rings can become a source of high-energy ring-shaped electron beams.

A hybrid discontinuous PWM algorithm of balancing neutral point voltage for 3L‐NPC inverter

AbstractWider linear modulation range, less switching loss, and simplicity are the goals pursued by various modulation methods of multilevel inverters. This paper proposes a new hybrid discontinuous pulsewidth modulation (HDPWM) strategy for three‐level neutral‐point‐clamped (3L‐NPC) inverter that can achieve the above goals to a certain extent. According to the position of the reference voltage vector and the actual situation of the neutral point voltage, different control modes and clamping types are selected. The neutral point voltage is controlled by DPWM strategy, which can not only greatly reduce the switch loss but also maintain the balance of the neutral point voltage and expand the linear modulation range. The implementation of the algorithm combines the advantages of carrier‐based PWM (CBPWM) and space vector PWM (SVPWM). There is no need to select the nearest three vectors (NTVs) and calculate their dwell time. Only the reference voltage needs to be modified according to the control requirements, and then by comparing the modified reference voltage with the carrier, the driver pulse required by the switching devices can be generated. Compared with the existing PWM methods, it is more simple and easy to implement. Experimental results verify the validity of the method.

Beam-based characterization of plasma density in a capillary-discharge waveguide

Next-generation plasma-based accelerators can push electron bunches to gigaelectronvolt energies within centimeter distances. In these devices, the accelerating force is provided by a driver pulse, either a laser pulse or a particle bunch, that loses its energy into the plasma generating huge electric fields up to tens of GV/m. The stability of such fields strongly depends on plasma density, whose exact value should be precisely known and controlled. However, currently available methods based on spectroscopic or interferometric techniques find it very difficult to measure plasma density lower than 1015–16 cm−3 in capillary-discharge waveguides. Here, we present a novel diagnostic tool that allows us to estimate the average density of a plasma capillary by probing it with an ultra-relativistic electron beam. The plasma density and the generated accelerating field are inferred by analyzing the beam longitudinal phase space after its interaction with the plasma. The results are validated by simulations showing excellent agreement.

First emittance measurement of the beam-driven plasma wakefield accelerated electron beam

Next-generation plasma-based accelerators can push electron beams to GeV energies within centimetre distances. The plasma, excited by a driver pulse, is indeed able to sustain huge electric fields that can efficiently accelerate a trailing witness bunch, which was experimentally demonstrated on multiple occasions. Thus, the main focus of the current research is being shifted towards achieving a high quality of the beam after the plasma acceleration. In this letter we present beam-driven plasma wakefield acceleration experiment, where initially preformed high-quality witness beam was accelerated inside the plasma and characterized. In this experiment the witness beam quality after the acceleration was maintained on high level, with $0.2\%$ final energy spread and $3.8~\mu m$ resulting normalized transverse emittance after the acceleration. In this article, for the first time to our knowledge, the emittance of the PWFA beam was directly measured.

Keldysh time bounds of laser-driven ionization dynamics.

We revisit the energy-time uncertainty underpinning of the pointwise bounds of laser-driven ionization dynamics. When resolved within the driver pulse and its field cycle, these bounds are shown to manifest the key signature tendencies of photoionization current dynamics-a smooth growth within the pulse in the regime of multiphoton ionization and an abrupt, almost stepwise photocurrent buildup within a fraction of the field cycle in the limit of tunneling ionization. In both regimes, the Keldysh time, defined as the ratio of the Keldysh parameter to the driver frequency, serves as a benchmark for the minimum time of photoionization, setting an upper bound for the photoelectron current buildup rate.

Energy spread minimization in a beam-driven plasma wakefield accelerator

Next-generation plasma-based accelerators can push electron bunches to gigaelectronvolt energies within centimetre distances. The plasma, excited by a driver pulse, generates large electric fields that can efficiently accelerate a trailing witness bunch making possible the realization of laboratory-scale applications ranging from high-energy colliders to ultra-bright light sources. So far several experiments have demonstrated a significant acceleration but the resulting beam quality, especially the energy spread, is still far from state of the art conventional accelerators. Here we show the results of a beam-driven plasma acceleration experiment where we used an electron bunch as a driver followed by an ultra-short witness. The experiment demonstrates, for the first time, an innovative method to achieve an ultra-low energy spread of the accelerated witness of about 0.1%. This is an order of magnitude smaller than what has been obtained so far. The result can lead to a major breakthrough toward the optimization of the plasma acceleration process and its implementation in forthcoming compact machines for user-oriented applications.

High-order harmonic generation in doped diamond: comparison of light and heavy regimes

The electronic response of crystalline n-doped diamond in light and heavy concentrations, as well as high harmonic generation following irradiation by a few cycles high-intensity laser pulse are calculated by modeling the dynamics in the framework of combined time-dependent density functional theory and virtual crystal approximation. The driver pulse frequencies are above and below the band gap frequency. The comparison of transient optoelectronic properties between two regimes shows that light doping enhances the magnitude of HHG. Further, the above gap irradiated doped diamond in both regimes represents much bright harmonics than below gap one. Modulations of the transient effective mass under irradiation of femtosecond laser are analyzed for both doping rates over the Brillouin zone. Comparison of the spectrum from virtual crystal approximation with available harmonic data of dielectric materials from real defected supercell calculations shows the important contribution of ionic relaxation in the description of nonlinear optical properties.

Relativistic cavity, possibilities, and advantages

AbstractThe relativistic mirror (RM) is an interesting subject which introduced in the nonlinear regime of the laser–plasma interaction. Reflection of counter-propagating probe pulse from relativistic flying mirror has some excellent features, such as frequency up-shifting and compressing by a factor of 4γ2. In the high-intensity laser–plasma interaction, sometimes a sequence of RMs creates. For example, electron density cusps generate in the nonlinear laser wakefield generation or flying electron sheaths create in the blown-out regime of the laser foil interaction. Under these circumstances, the second counter-propagated seed (probe) pulse can be reflected back and forth between two or more successive RMs. This structure may be used as a relativistic cavity (RECA). Amplification and threshold conditions for the gain medium and pumping rate in the RECA are obtained, and it is shown that amplification can be started from background simultaneous emission (without seed pulse). A new feature of RECA is it's bidirectional (two frequencies) characteristic. Thereupon, the gain process can be implemented on the two different transitions in this bidirectional gain structure. In the RECA, driver pulse may be assembled as a pumping operation, and background plasma medium with high degree ionized substances is a good candidate for gain medium in the UV or X-ray regions. In this paper, we propose a new all-optical cavity for the generation of the ultrashort laser pulse in the UV or X-ray regions.

Regulating the higher harmonic cutoffs via sinc pulse

We theoretically investigate the generation of higher harmonics and the construction of a single attosecond pulse (ASP) by means of two oppositely polarized sinc-shaped driver pulses. In comparison to a few-cycle Gaussian pulse of the same energy, here we observe a significant broadening in the bandwidth of the XUV/soft x-ray supercontinuum spectrum in the synthesized pulse. Furthermore, we observe that the harmonic cutoff and its corresponding intensity follow a well-defined scaling with the delay parameter between the two pulses. In principle, this delay can easily be tuned on an optical bench. The typical nature of the synthesized pulse ensures the generation of a single ASP instead of a pulse train. In this case, we obtain a single ASP with a duration of ∼27 attoseconds in the XUV/soft x-ray regime of the electromagnetic spectrum. Depending on the delay parameter we observe an enhancement in some satellite harmonics. The proposed setup promises a highly tunable source of energetic photons, wherein the energy of the photons can easily be controlled from the XUV to the soft x-ray regime by simply changing the delay between two oppositely polarized sinc-pulses.

An Improved Power Management System in Electrosurgery Unit Monopolar Design

In using the Electrosurgery unit, improper power settings and modes can cause tissue damage, so it is necessary to adjust the cutting mode and power settings needed. The purpose of this research is to design power control and cutting mode in Electrosurgery using Arduino nano as a regulator of power and pulse or duty cycle. The contribution of this research is the creation of power control and mode in the Electrosurgery unit to increase power and cutting mode. This is to control the electrosurgery power. The LM2907 IC frequency to voltage circuit is used as a voltage regulator, which is issued according to the frequency with the power selection LOW, MEDIUM, HIGH. The method used is the CMOS 4069 device as a frequency generator at 250 kHz, then the driver pulse is passed and controlled by the ATmega328 IC, then forwarded to an inverter circuit that functions to increase the voltage and output in the form of power. After the measurement process is carried out on the inverter input with a Blend mode three value, the voltage value is obtained at the low setting 100 V error 0.03%, medium setting 110V error 0.02%, High setting 120 V Error -0.02%. While the measurement results in the coagulation mode are the low setting error of 100 V 0.05%, the medium setting error is 110V 0.08%. High setting error is 130 V 0.003%. The measurements show that the error in power management is lower than 1%. The results of this study can be implemented in the electrosurgery unit to reduce tissue damage due to a lack of cutting modes and power management.