Liu Shi-Bing

A new approach of solving Green's function for wave propagation in an inhomogeneous absorbing medium

A new approach is developed to solve the Green’s function that satises the Hehmholtz equation with complex refractive index. Especially, the Green’s function for the Helmholtz equation can be expressed in terms of a one

Quantization of the radiation field in an anisotropic dielectric medium

There are both loss and dispersion characteristics for most dielectric media. In quantum theory the loss in medium is generally described by Langevin force in the Langevin noise (LN) scheme by which the quantization of the radiation field in various homogeneous absorbing dielectrics can be successfully actualized. However, it is invalid for the anisotropic dispersion medium. This paper extends the LN theory to an anisotropic dispersion medium and presented the quantization of the radiation field as well as the transformation relation between the homogeneous and anisotropic dispersion media.

Analysis of X-Ray Photoelectron Spectroscopy of Polymethyl Methacrylate Etched by a KrF Excimer Laser

The C 1s and O 1s electrons in polymethyl methacrylate etched by different incident laser intensities are analysed by x-ray photoelectron spectroscopy. The results show that when the incident laser fluence increases gradually, the percentage of carbon atoms in C–C bonds decreases while the one in carbonyl group (C=O) and alkoxy group (C–O) increases, and the percentage of oxygen atoms in C=O bonds increases while the one in C–O bonds decreases. Based on the analysis of the chemical structure, the energy level transition, energy diversion, and dissociation of bonds are theoretically examined, which is consistent with the experimental results.

Intense Cherenkov-type terahertz electromagnetic radiation from ultrafast laser—plasma interaction

A Cherenkov-type terahertz electromagnetic radiation is revealed, which results efficiently from the collective effects in the time-domain of ultrafast pulsed electron current produced by ultrafast intense laser—plasma interaction. The emitted pulse waveform and spectrum, and the dependence of laser pulse parameters on the structure of the radiation field are investigated numerically. The condition of THz radiation generation in this regime and Cherenkov geometry of the radiation field are studied analytically.

Dynamic Characteristics of Growing Modes of Raman Instability from Intense Laser Beam Propagating Through Plasma

An essential dispersion relation, which can describe the dynamic properties of stimulated Raman scattering instability as a laser beam propagates through plasmas, is derived analytically. The development of growth mode, angle distribution, and temperature dependence of the instabilities are presented by solving this dispersion relation numerically. A significant dynamic characteristic has been revealed that the temperature increasing of the electron would result in redshift of scattered spectrum at high laser intensities. Furthermore, a novel modulational instability with double-peak temporal structure appears in a limited density region because of the coupling of scattered upshift and downshift waves.

Spectral enhancement of thermal radiation by laser fabricating grating structure on nickel surface

Previous studies have shown some correlations between the optical properties of objects and their surface patterns. We fabricate tens of micrometer period gratings by femtosecond laser direct writing technology on polished nickel targets and measure their thermal radiation spectra at a temperature of 623 K by Fourier transform infrared (FTIR) spectrometry. The results show an obvious major enhanced peak in which the wavelength is slightly larger than the grating period. Surface plasmon resonance (SPR) and Kirchhoffs law of thermal radiation are applied to give this phenomenon a preliminary explanation. In addition, we utilized rigorous coupled wave analysis (RCWA) to simulate the absorption spectrum of the grating surface. The experiment results show good agreement with the simulation results.

Modulation of ionization on laser frequency in ultra-short pulse intense laser-gas-target

Based on the dispersion relation of intense laser pulse propagating in gradually ionized plasma, this paper discusses the frequency modulation induced by ionization of an ultra-short intense laser pulse interacting with a gas target. The relationship between the frequency modulation and the ionization rate, the plasmas frequency variation, and the polarization of atoms (ions) is analysed. The numerical results indicate that, at high frequency, the polarization of atoms (ions) plays a more important role than plasma frequency variation in modulating the laser frequency, and the laser frequency variation is different at different positions of the laser pulse.

Nonlinear Characteristics of an Intense Laser Pulse Propagating in Partially Stripped Plasmas

The nonlinear optic characteristics of an intense laser pulse propagating in partially stripped plasmas are investigated analytically. The phase and group velocity of the laser pulse propagation as well as the three general expressions governing the nonlinear optic behavior, based on the photon number conservation, are obtained by considering the partially stripped plasma as a nonlinear optic medium. The numerical result shows that the presence of the bound electrons in partially stripped plasma can significantly change the propagating property of the intense laser pulse.

Stimulated Emission of Gamma Photon from Ultrashort Pulse Intense Laser-Solid-Target Interaction*

The efficient production of energetic gamma photons is a significant physical process in the relativistic ultrashort pulse laser-plasma inducing photonuclear action. Based on the interaction of laser-solid-target, an analytical theory on stimulated gamma photon emission from a hot electron Bring the target-nucleus is developed by a relativistic full quantum method. The emitting power or probability of gamma photon in arbitrary space direction can be calculated for laser irradiating solid-target normally. It is valid only if the scatter-centre is immovable or its motion can be neglected compared with that of the scattered electrons.