光在介质中的折射

研究了光的磁场在光与介质相互作用中的行为,建立了电子云导体模型,即介质中一个电子的电子云可以看作是一个微小导体,光变化的磁场与电子云导体间的电磁感应作用导致光与电子云导体之间的能量交换。光在介质中速度减慢起因于这种能量交换。应用电子云导体模型和能量守恒原理,导出了介质折射率表达式,并利用这个表达式计算了几种介质的折射率,计算结果与实测值符合得很好。解释了折射率的各向异性,以及静电场或静磁场对介质折射率的影响。     

Refraction of light in media

The roles of the magnetic field and electric field of the light are investigated when the light is refracted in the medium. The model of the electron cloud conductor is presented. Electron cloud in a molecule is treated as a conductor and the Faraday’s Law is applied to this conductor that is in the alternating magnetic field of the light. dB _M/dt of the light gives rise to an alternating induced current on the electron cloud conductor, and the light exchanges energy, i.e. the refractive energy, with the electron cloud conductor. Formulas of refractive index, which is the ratio of light speed in vacuum to that in the medium, are derived with this model. These formulas are tested with several mediums and Langevin’s diamagnetic susceptibility of helium gas, and the results are in good agreement with the measured data. The anisotropy and the nonlinearity of the refractive index are explained with the theory described in this work. Supported by Beijing Science and Technology New Star Program (Grant No. 952870400), the Beijing Municipal Commission of Education and the Excellent Young Teachers Program of Ministry of Education of China     

Particle nature of light waves in dielectric media

Wave-particle duality is a foundation for modern science. The speed of light waves in dielectric media is less than c. The corresponding particles thus have mass. Combining wave-particle duality with the theory of relativity, an exactly solvable problem was proposed, concerning the transition from photons in vacuum to particles in dielectric media. The rest mass, the momentum, and the total energy of material particles are shown to be the functions of the refractive index of the medium and the wavelength of the incident light. The proposed relationships were applied to study the wavelength-dependent index of refraction of dielectrics and the correlation of the refractive indices of anisotropic crystals, which were confirmed by the experimental results. Variation of the refractive index with wavelength is found to obey the proposed relation. The refractive indices of anisotropic crystals are shown to be the correlated quantities.     

带有增益的单微环谐振器的光速控制行为

带有损耗的光波导微环谐振器在实现光速控制时存在输出脉冲能量损耗大、脉冲形状畸变严重等问题。基于带有增益和带有损耗的微环谐振器的传输特性之间的对称性,计算分析了单微环谐振器的透射率、群折射率和群速度色散等特性,分析了增益和损耗对微环谐振器输出特性影响的机制。计算了带有增益的微环谐振器的光速控制行为,并与带有损耗的微环谐振器进行对比。结果显示,带有增益的微环谐振器输出脉冲不分裂且有较大的输出强度。脉冲延迟量和超前量比损耗系统大,可用于光速控制,克服了微环带有损耗时产生的光强损耗和脉冲畸变。     

基于线偏振光反射率测量介质折射率的研究

研究线偏振光的振幅反射率与介质折射率的关系,提出一种测量介质材料折射率的方法。文中从菲涅耳公式出发,推导出各向同性介质的线偏振光反射率与折射率的关系式,给出基于线偏振光反射率测定介质折射率的原理。设计实验方案,在不同入射角情况,定出线偏振光p方向和s方向两种线偏振光在玻璃表面的反射率,得到线偏振光振幅反射率随入射角变化的实验曲线。依此实验数据得出材料的折射率。结果表明,测出的介质材料的折射率与理论值相符,所采取的测定方案可行。     

水平极化光在单轴吸收晶体中的传播

根据光在各向同性吸收介质中传播的分析方法,引入了波法线矢量传播常量,讨论了水平极化光在单轴吸收晶体中的传播规律,得到了波法线折射率、光线折射率、吸收系数等描述吸收晶体性质和光传播性质的物理量的表达式,推导出透明晶体的相应公式.数值计算表明,由该法得到的晶体表面的反射和透射系数与用复折射率表示法得到的结论一致.     

Casimir energy for a dielectric cylinder

In this paper, we calculate the Casimir energy for a dielectric-diamagnetic cylinder with the speed of light differing on the inside and outside. Although the result is in general divergent, special cases are meaningful. The well-known results for a uniform speed of light are reproduced. The self-stress on a purely dielectric cylinder is shown to vanish through second order in the deviation of the permittivity from its vacuum value, in agreement with the result calculated from the sum of van der Waals forces. These results are unambiguously separated from divergent terms.     

Total internal reflection at a boundary between vacuum and an optical medium with quasi-zero refractive index

It is shown that, on a surface of optical transparency of a medium with quasi-zero refractive index, surface optical waves traveling along the surface can be excited for different angles of incidence of external radiation. Expressions for the amplitudes of nonspecular reflection and transmission of light waves at an inhomogeneous boundary between two media are derived. Using these expressions, the boundary reflectance and transmittance for different angles of incidence and refraction can be calculated.     

Cherenkov Radiation in Moving Medium

Cherenkov radiation in uniformly moving homogeneous isotropic medium without dispersion is studied. Formula for the spectrum of Cherenkov radiation of fermion was derived for the case when the speed of the medium is less than the speed of light in this medium at rest. The properties of Cherenkov spectrum are investigated.     

利用强度周期性变化的光信号测量光速与介质的折射率

介绍了一种利用强度周期性变化的光信号来测量光速与介质折射率的方法,可以精确测量出光传播距离改变cm数量级时光传播时间的改变.如果在光路中放入介质,用这种方法可以很精确地测量出由此引入的光程差,并给出了一个测量介质折射率的新方法.     

Thermal and acoustic effects in absorbing liquids under the action of pulsed light beams

We present the results from simulating the impact of pulsed light beams of different spatial structures (Gaussian, Bessel, singular) in absorbing liquids. Profiles of refractive index inhomogeneities excited in a medium are calculated and the kinetics of their relaxation is studied.     

Comparison of various approaches to the calculation of optically induced forces

Various approaches used for the calculation of optically induced forces applied to a transparent optical medium imbedded in a close plane optical resonator are analyzed. The forces are calculated by means of analysis of a change in the eigen frequency and energy stored in the resonator at various positions of the medium. It is shown that results obtained are identical to those calculated by means of approaches based on the Maxwell stress tensor, based on an analysis of a change in the momentum of light. An exception is for results obtained on the base of last versions of the Lorentz density force.     

基于磁流体光子晶体的可调谐近似零折射率研究

基于典型水基Fe_3O_4磁流体,建立了工作频率可调的近似零折射率磁流体光子晶体的理论模型.这种近似零折射率材料具有与自由空间阻抗相匹配的优点,更重要的是其工作频率可由外磁场的大小来调节.在满足等效折射率的绝对值小于0.05的条件下,材料的归一化工作频率可由0.716变化到0.750.     

Brueckner theory and Jastrow approach for finite nuclei

The results of Jastrow variational calculations and of Brueckner theory in lowest order (Brueckner-Hartree-Fock) are compared. The comparison is made for the calculations of ground state properties like binding energy and charge-radius of light and medium weight, closed shell nuclei (⁴He, ¹⁶O, ⁴⁰Ca). For the nucleon-nucleon interaction rather simple forces are used (Brink-Boeker potential B1, Afnan-Tang potential S3). For all cases considered it turns out that the results of the two different methods are in fairly good agreement, with the binding energy calculated in the Brueckner-Hartree-Fock approximation being always slightly below the corresponding upper bounds calculated in the Jastrow variational approach. This good agreement between the two methods indicates, that for light and medium weight nuclei the Jastrow variational approach and the Brueck-ner-Hartree-Fock approximation can be considered as reasonable approximations to a complete solution of the many-body problem.     

Energy Characteristics of Wave Fields Radiated from Elementary Oscillators in a Nondispersive Medium Moving with Subluminal Velocity

We study the energy characteristics of fields radiated from electric, magnetic, and toroidal dipoles in a nondispersive medium moving with velocity lower than the speed of light in this medium. The angular dependences of Abraham's energy-flux density of electromagnetic field are analyzed. In particular, it is shown that if the medium velocity is high enough, then the radial component of the vector of energy-flux density is negative in a certain angular range. Expressions for the electromagnetic energy flux through a sphere of large radius are obtained. It is shown that if the velocity of a moving medium is high enough, then the energy flux is negative and its absolute value can exceed the energy losses of sources.     

Simulation of light generation in cholesteric liquid crystals using kinetic equations: Time-independent solution

We report on the results of calculating the conditions for light generation in cholesteric liquid crystals doped with fluorescent dyes using kinetic equations. Specific features of spectral properties of the chiral cholesteric medium as a photonic structure and spatially distributed type of the feedback in the active medium are taken into account. The expression is derived for the threshold pump radiation intensity as a function of the dye concentration and sample thickness. The importance of taking into account the distributed loss level in the active medium for calculating the optimal parameters of the medium and for matching the calculated values with the results of experiments is demonstrated.     

On the supraluminal group velocity and the transmission of information

The calculations are reported indicating that the transmission of information through a medium with the frequency dispersion of the refractive index n(ω), where the group velocity is higher than the speed of light in vacuum, always occurs exactly with the speed of light in vacuum. This result is valid for any functional dependence n(ω).     

Effect of light with varying amplitude and frequency on a medium

A formula for the complex refractive index of a medium exposed to light whose amplitude and frequency are varied in time is derived.     

Monoenergetic electron parameters in a spheroid bubble model

A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived.The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately,especially at the relativistic region.The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model.The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons △E/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions.As a result,the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model.     

Theory of light scattering by acoustic modes on liquids interfaces

A theory of light scattering from the surface of a highly opaque metallic liquid bounded by a transparent medium is developed using a linear response function theory. The light scattering cross section is calculated taking only the ripple mechanism into account in the two media. Two limit cases are also derived and it is shown that they are in agreement with previous theories. Numerical results are also presented and in particular it is shown that our theoretical spectrum is in good agreement with the experimental data.Work Partially Supported by the Brazilian Research Councils CNPq and FINEP