Hongyu Zhou

• Lecturer at National University of Defense Technology

We present a novel method for optimizing surface modulation structures of solid targets to enhance ion beam yield via the target normal sheath acceleration mechanism. For the initially set conical target, we used a random walk sampling algorithm to optimize the microstructure on the conical surface. With only 36 simulations, we achieved the optimiz...

The influence of laser intensity on the resistive filamentation during intense electron beam transport in aluminum targets is investigated through theoretical analysis and three-dimensional hybrid simulations. Analysis of linear filamentation instabilities indicates that resistive filamentation is more likely to occur under high laser-intensity con...

We present a robust and effective scheme of high harmonic generation (HHG) from relativistic plasmas driven by dual laser fields. The theoretical analysis and particle-in-cell simulation results reveal that quasi-circularly polarized (CP) harmonics can be acquired due to the joint action of the P-polarized pump pulse and the CP seed pulse. In addit...

Suppression of the stimulated Raman scattering (SRS) by a stochastic phase low-coherence laser (SPLL) in homogeneous plasma is investigated by theoretical analysis and one-dimensional particle-in-cell (PIC) simulation. A simple model is established, in which the SPLL is modelled as a combination of a monochromatic laser and a broadband laser. When...

We present an investigation of high harmonic generation (HHG) from relativistic plasmas driven by two-color co-rotating circularly polarized (CP) laser fields at various frequency ratios [Formula: see text]. The theoretical analysis and the particle-in-cell simulation results reveal that when [Formula: see text], CP harmonics with opposite heliciti...

Vortex beams with ultra-high brilliance can greatly enrich the light and matter interaction process and even shed light on the unexpected information in relativistic nonlinear optics. Thus, we propose a scheme for relativistic intense vortex harmonic radiation by use of bi-circular Laguerre–Gaussian lasers irradiating relativistic plasmas. Three-di...

The parametric instability related to ion motion and the resulting cross beam energy transfer are important contents in the physics of inertial confinement fusion. The numerical simulation of the above physical problems still faces great technical challenges. This paper introduces a twodimensional hybrid-kinetic particle-in-cell (PIC) code: CBETor....

High harmonic generation (HHG) by two-color counter-rotating relativistic laser pulses with arbitrary frequency ratio is investigated through particle-in-cell simulations. It is shown that the dichromatic laser driver at various frequency ratios can effectively produce high-order harmonics with different spectral features. A general selection rule...

Ion acceleration with linearly polarized 1 petawatt (PW) intense laser pulses interacting with near critical density (NCD) gas targets was demonstrated by using two-dimensional (2D) particle-in-cell (PIC) simulations. The laser parameters considered are comfortably within the capabilities of PW laser facilities, e.g., Extreme Light Infrastructure -...

By using three-dimensional particle-in-cell simulations, we demonstrate that an energetic ring-shaped ion beam can be generated by an ultra-intense circularly polarized Laguerre–Gaussian laser pulse interacting with micro-structure targets. The electron and ion dynamics of three different targets including a sleeve–wire target, wire target, and com...

Particle-in-cell (PIC) simulations are used to study the nonlinear process of stimulated Raman scattering (SRS) excited by a rotated polarized laser interacting with underdense plasmas. The influence of the rotating frequency on linear SRS growth rate is theoretically analyzed and the long-term nonlinear SRS behavior excited by the rotated polarize...

In this paper, we propose a robust and novel scheme to generate ultra-bright circularly polarized harmonics using non-collinear double-circularly polarized laser pulses irradiating over-dense plasma surface. Numerous advantages are demonstrated by three-dimensional particle-in-cell simulations including high efficiency of harmonic generation, the s...

Polarization grating (PG) is a kind of optical element based on the Pancharatnam-Berry phase, providing a unique capability of manipulating the polarization properties of output beams [Bomzon et al., Opt. Lett. 27, 1141–1143 (2002) and Oh and Escuti, Opt. Lett. 33, 2287–2289 (2008)]. Here, we extend this concept into the nonlinear domain of high-or...

Nonlinear behaviors of stimulated Raman scattering driven by finite bandwidth pumps are studied by one dimensional particle-in-cell simulations. The broad spectral feature of plasma waves and backscattered light reveals the different coupling and growth mechanisms, which lead to the suppression effect before the deep nonlinear stage. It causes nonp...

Extreme ultra-violet (XUV) light and soft X-ray are widely used to detect the microscopic structure and observe the ultra-fast physical process. It is found that high order harmonic with the frequency as high as that of the waterwindow waves and the pulse duration as short as attosecond can be obtained in the laser-plasma interaction. Due to these...

The simple surface current model is extended to study the generation of high-order harmonics for a relativistic circularly polarized laser pulse interacting with a plasma grating surface. Both exact relativistic electron dynamics and optical interference of surface periodic structure are considered. It is found that high order harmonics in the spec...

In high-power microwave (HPM) area, increasing the cross-sectional dimension makes the device work in overmoded state, is an efficient way to improve the device's power handling capacity. However, the high order mixed modes may decrease the efficiency of the microwave output. Therefore, it is necessary to study the mixed modes in overmoded waveguid...

Transmit-array (T-A) design for circular polarization made by all-metal is presented in this work. The proposed T-A consists of numerous cross-slot elements. The simulation results indicate that rotating the cross slot on the element, a full transmission phase range of 360°can be achieved for a transmission magnitude better than -0.6 dB at 9.375 GH...

Generation of intense coherent THz radiation by obliquely incidenting an intense laser pulse on a wire target is studied using particle-in-cell simulation. The laser-accelerated fast electrons are confined and guided along the surface of the wire, which then acts like a current-carrying line antenna and under appropriate conditions can emit electro...

Harmonic generation from linearly polarized high-intensity short-pulse laser normally impacting a solid plasma grating is investigated using analytical modeling and particle-in-cell simulation. It is found that when the radiation excited by the relativistic electron quiver motion in the laser fields suitably matches a harmonic of the grating period...

The carbon nanotube (CNT)-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the...

Usually, the high-power microwave (HPM) devices suffer from impedance collapse and cathode material degradation or even failure. When the intense electron beam bombards the anode (or named as collector in HPM device), an anode plasma could appear under certain conditions. In this case, the impedance collapse is caused by the expansions of the catho...

Anode plasma generated by electron beams could limit the electrical pulse-length, modify the impedance and stability of diode, and affect the generator to diode power coupling. In this paper, a particle-in-cell code is used to study the dynamics of anode plasma in the high-power electron beam diode. The effect of gas type, dynamic characteristic of...

The tunable capability expands the application fields of backward wave oscillator (BWO), especially for large range modulation. This paper presents analysis, PIC simulation, and preliminary design of a novel relativistic BWO which achieves the purpose of modulation among three or more frequencies within two bands. A new dielectric slow-wave structu...