This paper derives the force of the electromagnetic radiation on left-handed materials （LHMs） by a direct application of the Lorentz law of classical electrodynamics. The expressions of radiation force are given for TE-polarised and TM-polarised fields. The numerical results demonstrate that electromagnetic waves exert an inverse lateral radiation force on each edge of the beams, that is, the lateral pressure is expansive for TE-polarised beams and compressive for TM-polarised beams. The investigation of the radiation force will provide insights into the fundamental properties of LHMs and will provide to better understanding of the interaction of light with LHMs.
The influence of the amplitude ratio between the two THz pulses on two-dimension THz spectroscopy(2DTS)has been studied theoretically via a classical method in which the expressions for the second-order nonlinearity were derived using perturbation approach,and the THz pulses were not treated as a delta function.Three types of nonlinear sources i.e.,anharmonicity,nonlinear damping,and nonlinear coupling,are considered in a single mode system.The simulation results demonstrated that the amplitude ratio had a notable influence on the 2DTSs,and different sources have different influences.This study is promising for guiding future experiments.
Jiangsheng HuJinsong LiuHuquan LiKejia WangZhengang YangShenglie Wang
The transmission property of microwave through a kind of metamaterial is investigated experimentally.Such metamaterials are fabricated with a structure of double sets of square holes:subwavelength ones,and small ones whose sizes and spacing are smaller at least one order of magnitude than those of the subwavelength holes.The experimental results show that the peak power of the measured transmission spectra is dependent on the structure parameters of the small holes.The physical origin to create this phenomenon is that the designer surface plasmons sustained by the small holes affect on the transmission property of the microwave passing through the subwavelength holes.The results are promising for proposing some techniques for optoelectronic devices in terahertz and microwave regime.
中草药分析与鉴定对中草药质量控制意义重大，以飞秒激光为基础的太赫兹时域光谱技术（T Hz-TDS）是一种新型相干远红外光谱测量技术。为了研究基于太赫兹谱的中药材鉴别可行性，应用 T Hz-TDS研究了室温下黄芪、当归、杜仲及三种掺杂的黄芪在0.2～2.2 T Hz范围内的光学特性，得到了对应的时域谱、频域谱和吸收谱。结果表明在此波段三种中草药的时域谱、频域谱及吸收谱存在显著差异；三种掺杂黄芪的频域谱、吸收谱虽相似但也有明显不同。利用太赫兹时域光谱技术鉴别中药材是可行的，它可为中草药质量控制提供一种新的方法。
The dielectric properties of near-stoichiometric LiNbO3：Fe and LiNbO3：Ce single crystals have been investigated using terahertz time domain spectroscopy in a frequency range of 0.71.6 THz at room temperature. When coupled with an applied external optical field, obvious photorefractive effects were observed, resulting in a modulation of the complex dielectric constant for the crystals. The variation in refractive index, ｜△n｜, had a linear relationship with the applied light intensity, accompanied by a step-like decrease at high intensity. The findings were attributed to the internal space charge field of the photorefraction and the light-induced domain reversal in the crystals.
A four-wave mixing （FWM） model is used to analyze the polarization control of terahertz （THz） pulse generated by a two-color laser field in air. The analytic formula for the THz intensity varying with the THz polarizer angle, and the relative phase between the two pulses, are obtained. The corresponding numerical results agree well with both numerical result obtained from a quantum model and measured data reported. Moreover, possible phenomena are predicted for variables not found in other experiments. Compared with the quantum model, the FWM model gives analytic formulas and clear physical pictures, and has the advantage of efficient computing time.
