The phase summation effect in sum-frequency mixing process is utilized to avoid a nonlinearity obstacle in the power scaling of single-frequency visible or ultraviolet lasers.Two single-frequency fundamental lasers ar...The phase summation effect in sum-frequency mixing process is utilized to avoid a nonlinearity obstacle in the power scaling of single-frequency visible or ultraviolet lasers.Two single-frequency fundamental lasers are spectrally broadened by phase modulation to suppress stimulated Brillouin scattering in fiber amplifier and achieve higher power.After sum-frequency mixing in a nonlinear optical crystal,the upconverted laser returns to single frequency due to phase summation,when the phase modulations on two fundamental lasers have a similar amplitude but opposite sign.The method was experimentally proved in a Raman fiber amplifier-based laser system,which generated a power-scalable sideband-free single-frequency 590 nm laser.The proposal manifests the importance of phase operation in wave-mixing processes for precision laser technology.展开更多
The aim of this paper is to solve the two-dimensional acoustic scattering problems by random sphere using Electric field integral equation. Some approximations for the two-dimensional case are derived. These various a...The aim of this paper is to solve the two-dimensional acoustic scattering problems by random sphere using Electric field integral equation. Some approximations for the two-dimensional case are derived. These various approximations are next numerically validated in the case of high-frequency.展开更多
This study analyzes the linewidth narrowing characteristics of free-space-running Brillouin lasers and investigates the approaches to achieve linewidth compression and power enhancement simultaneously.The results show...This study analyzes the linewidth narrowing characteristics of free-space-running Brillouin lasers and investigates the approaches to achieve linewidth compression and power enhancement simultaneously.The results show that the Stokes linewidth behavior in a free-space-running Brillouin laser cavity is determined by the phase diffusion of the pump and the technical noise of the system.Experimentally,a Stokes light output with a power of 22.5 W and a linewidth of 3.2 kHz was obtained at a coupling mirror reflectivity of 96%,which is nearly 2.5 times compressed compared with the linewidth of the pump(7.36 kHz).In addition,the theorical analysis shows that at a pump power of 60Wand a coupling mirror reflectivity of 96%,a Stokes output with a linewidth of 1.6 kHz and up to 80%optical conversion efficiency can be achieved by reducing the insertion loss of the intracavity.This study provides a promising technical route to achieve high-power ultra-narrow linewidth special wavelength laser radiations.展开更多
Laser pulses of 200 ps with extremely high intensities and high energies are sufficient to satisfy the demand of shock ignition,which is an alternative path to ignition in inertial confinement fusion(ICF).This paper r...Laser pulses of 200 ps with extremely high intensities and high energies are sufficient to satisfy the demand of shock ignition,which is an alternative path to ignition in inertial confinement fusion(ICF).This paper reports a type of Brillouin scheme to obtain high-intensity 200-ps laser pulses,where the pulse durations are a challenge for conventional pulsed laser amplification systems.In the amplification process,excited Brillouin acoustic waves fulfill the nonlinear optical effect through which the high energy of a long pump pulse is entirely transferred to a 200-ps laser pulse.This method was introduced and achieved within the SG-Ⅲprototype system in China.Compared favorably with the intensity of 2 GW/cm^2 in existing ICF laser drivers,a 6.96-GW/cm^2 pulse with a width of 170 ps was obtained in our experiment.The practical scalability of the results to larger ICF laser drivers is discussed.展开更多
A high-frequency analytical solution for scattering of Rayleigh waves by a shallow circular alluvial valley was derived using wave function expansion method, and the solution was utilized to analyze the effects of inc...A high-frequency analytical solution for scattering of Rayleigh waves by a shallow circular alluvial valley was derived using wave function expansion method, and the solution was utilized to analyze the effects of incident frequency, width of the valley, and depth of the valley, etc, on the wave scattering. Numerical results showed that, because of the alluvial valley, the distribution of surface displacement at the side where wave arrives becomes relatively complicated, but the displacement amplitude is not large; the distribution of the surface displacement at far side is relatively simple, but the displacement amplitude is relatively large, and in most cases the amplitude is larger than that at the alluvium.展开更多
We present a theoretical investigation of the scattering of high frequency S0 Lamb mode from a circular blind hole defect in a plate based on the 3D theory. The SO wave is incident at the frequency above the A1 mode c...We present a theoretical investigation of the scattering of high frequency S0 Lamb mode from a circular blind hole defect in a plate based on the 3D theory. The SO wave is incident at the frequency above the A1 mode cut-off frequency, in which the popular approximate plate theories are inapplicable. Due to the non-symmetric blind hole defect, the scattered fields will contain higher order converted modes in addition to the fundamental SO and AO modes. The far-field scattering amplitudes of various propagating Lamb modes for different hole sizes are inspected. The results are compared with those of lower frequencies and some different phenomena are found. Two-dimensional Fourier transform （2DFT） results of transient scattered Lamb and SH wave signals agree well with the analytical dispersion curves, which check the validity of the solutions from another point of view.展开更多
We consider scattering of a time harmonic incident plane wave by a convex polygon with piecewise constant impedance boundary conditions.Standard finite or boundary element methods require the number of degrees of free...We consider scattering of a time harmonic incident plane wave by a convex polygon with piecewise constant impedance boundary conditions.Standard finite or boundary element methods require the number of degrees of freedom to grow at least linearly with respect to the frequency of the incident wave in order to maintain accuracy.Extending earlier work by Chandler-Wilde and Langdon for the sound soft problem,we propose a novel Galerkin boundary element method,with the approximation space consisting of the products of plane waves with piecewise polynomials supported on a graded mesh with smaller elements closer to the corners of the polygon.Theoretical analysis and numerical results suggest that the number of degrees of freedom required to achieve a prescribed level of accuracy grows only logarithmically with respect to the frequency of the incident wave.展开更多
基金The work was partly supported by the National Natural Science Foundation of China(No.62075226).
文摘The phase summation effect in sum-frequency mixing process is utilized to avoid a nonlinearity obstacle in the power scaling of single-frequency visible or ultraviolet lasers.Two single-frequency fundamental lasers are spectrally broadened by phase modulation to suppress stimulated Brillouin scattering in fiber amplifier and achieve higher power.After sum-frequency mixing in a nonlinear optical crystal,the upconverted laser returns to single frequency due to phase summation,when the phase modulations on two fundamental lasers have a similar amplitude but opposite sign.The method was experimentally proved in a Raman fiber amplifier-based laser system,which generated a power-scalable sideband-free single-frequency 590 nm laser.The proposal manifests the importance of phase operation in wave-mixing processes for precision laser technology.
文摘The aim of this paper is to solve the two-dimensional acoustic scattering problems by random sphere using Electric field integral equation. Some approximations for the two-dimensional case are derived. These various approximations are next numerically validated in the case of high-frequency.
基金the National Natural Science Foundation of China(No.61927815)the Natural Science Foundation of Tianjin City(Nos.22JCYBJC01100 and 20JCZDJC00430)+4 种基金the Shijiazhuang Overseas Talents Introduction Project(No.20230004)the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices(No.KF202201)Funds for Basic Scientific Research of Hebei University of Technology(No.JBKYTD2201)D.J.acknowledges the support from the Postgraduate Innovation Ability Training Program of Hebei Province(No.CXZZBS2021030)R.P.M.acknowledges the support from the Asian Office of Aerospace Research and Development(AOARD).
文摘This study analyzes the linewidth narrowing characteristics of free-space-running Brillouin lasers and investigates the approaches to achieve linewidth compression and power enhancement simultaneously.The results show that the Stokes linewidth behavior in a free-space-running Brillouin laser cavity is determined by the phase diffusion of the pump and the technical noise of the system.Experimentally,a Stokes light output with a power of 22.5 W and a linewidth of 3.2 kHz was obtained at a coupling mirror reflectivity of 96%,which is nearly 2.5 times compressed compared with the linewidth of the pump(7.36 kHz).In addition,the theorical analysis shows that at a pump power of 60Wand a coupling mirror reflectivity of 96%,a Stokes output with a linewidth of 1.6 kHz and up to 80%optical conversion efficiency can be achieved by reducing the insertion loss of the intracavity.This study provides a promising technical route to achieve high-power ultra-narrow linewidth special wavelength laser radiations.
基金supported in part by the National Natural Science Foundation of China (NSFC) (No. 61622501)the China Postdoctoral Science Foundation (No. BX20180085)
文摘Laser pulses of 200 ps with extremely high intensities and high energies are sufficient to satisfy the demand of shock ignition,which is an alternative path to ignition in inertial confinement fusion(ICF).This paper reports a type of Brillouin scheme to obtain high-intensity 200-ps laser pulses,where the pulse durations are a challenge for conventional pulsed laser amplification systems.In the amplification process,excited Brillouin acoustic waves fulfill the nonlinear optical effect through which the high energy of a long pump pulse is entirely transferred to a 200-ps laser pulse.This method was introduced and achieved within the SG-Ⅲprototype system in China.Compared favorably with the intensity of 2 GW/cm^2 in existing ICF laser drivers,a 6.96-GW/cm^2 pulse with a width of 170 ps was obtained in our experiment.The practical scalability of the results to larger ICF laser drivers is discussed.
基金National Natural Science Foundation of China (50378063) and the Program for New Century Excellent Talents in University
文摘A high-frequency analytical solution for scattering of Rayleigh waves by a shallow circular alluvial valley was derived using wave function expansion method, and the solution was utilized to analyze the effects of incident frequency, width of the valley, and depth of the valley, etc, on the wave scattering. Numerical results showed that, because of the alluvial valley, the distribution of surface displacement at the side where wave arrives becomes relatively complicated, but the displacement amplitude is not large; the distribution of the surface displacement at far side is relatively simple, but the displacement amplitude is relatively large, and in most cases the amplitude is larger than that at the alluvium.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11474195,11274226 and 61171145
文摘We present a theoretical investigation of the scattering of high frequency S0 Lamb mode from a circular blind hole defect in a plate based on the 3D theory. The SO wave is incident at the frequency above the A1 mode cut-off frequency, in which the popular approximate plate theories are inapplicable. Due to the non-symmetric blind hole defect, the scattered fields will contain higher order converted modes in addition to the fundamental SO and AO modes. The far-field scattering amplitudes of various propagating Lamb modes for different hole sizes are inspected. The results are compared with those of lower frequencies and some different phenomena are found. Two-dimensional Fourier transform （2DFT） results of transient scattered Lamb and SH wave signals agree well with the analytical dispersion curves, which check the validity of the solutions from another point of view.
文摘We consider scattering of a time harmonic incident plane wave by a convex polygon with piecewise constant impedance boundary conditions.Standard finite or boundary element methods require the number of degrees of freedom to grow at least linearly with respect to the frequency of the incident wave in order to maintain accuracy.Extending earlier work by Chandler-Wilde and Langdon for the sound soft problem,we propose a novel Galerkin boundary element method,with the approximation space consisting of the products of plane waves with piecewise polynomials supported on a graded mesh with smaller elements closer to the corners of the polygon.Theoretical analysis and numerical results suggest that the number of degrees of freedom required to achieve a prescribed level of accuracy grows only logarithmically with respect to the frequency of the incident wave.
