Controlling the diffused nonlinear light generated in random materials

We describe a method for shaping the wavefront of the second-harmonic light generated in nonlinear materials with a disordered structure using a spatial light modulator on the fundamental beam. We show that, for the case of a transparent strontium-barium niobate crystal with a random distribution of antiparallel domains, the speckle generation can be concentrated into a single spot.     

Equivalent volume-averaged light scattering behavior of randomly inhomogeneous dielectric spheres in the resonant range

Finite-difference time-domain numerical experiments and supporting analyses demonstrate that the spectral dependence of the total scattering cross sections of randomly inhomogeneous dielectric spheres of sizes in the resonant range closely resemble those of their homogeneous counterparts that have a volume-averaged refractive index. This result holds even for the extreme case in which the refractive index within an inhomogeneous sphere varies randomly over the range 1.0-2.0.     

Large energy behavior of the velocity distribution for the hard-sphere gas

The initial-value problem for the Boltzmann-Lorentz equation for hard spheres at zero temperature is shown to be ill defined, the general solution depending on an arbitrary function. The uniqueness of the solution can be obtained by imposing the conservation of the number of particles (Carleman's type of condition does not suffice). The linearized Boltzmann equation for hard spheres is then analyzed, as it occurs in Enskog's method for calculating transport coefficients. It is demonstrated that in the case of viscosity and diffusion it is necessary to add supplementary conditions to obtain the uniqueness of the solution. The nonuniform character of Enskog's expansion and violation of positivity in the large velocity region are exhibited.     

Isotropy of the velocity of light

Theories claiming existence of the anisotropy in the velocity of light are inconsistent with experimental data obtained by Mössbauer measurements.On leave from the Institute of Nuclear Physics, Kraków, ul. Radzikowskiego 152, Poland.     

关于探照灯照射的光斑速度

光速(真空中)是自然界物体运动或信息及能量传递的极限,如果不注意这个条件,一般地谈速度,那么,找寻超光速的现象并不是难事.有些教科书上时常以探照灯光斑移动的速度来阐述这种超光速现象,演算得到光斑移动的速度为v=hωcos2θ.本文指出,此结果是错的!对正确结果做的定量计算表明:光斑速度虽仍然能超光速,但正确结果的超光速条件远比错误结果的超光速复杂,而且物理含义也更加丰富.     

Generation of polarization-squeezed light in doped resonant media

The cross-interaction effects for a two-mode light pulse in an optical matrix doped with atoms that are resonant with the light in the presence of two control optical pump pulses (M scheme) have been analyzed. The fundamental possibility of effective generation of polarization-squeezed light in this system at a simultaneous nonlinear amplification of the probe field is shown. The optimal conditions for generating polarization-squeezed light in a doped optical fiber are found for different problem parameters.     

Formation of circular fringes with dark centre in diffused light at infinity

The generation of a circular fringe system of Newton rings' type with dark fringe at the centre is described. Such fringes are localized at infinity and are produced by a pair of longitudinally displaced mutually complimentary diffusers. Experimental results under various displacement configurations have been presented.     

光导纤维中光速的实验测定

介绍了光导纤维中光速测定的基本原理。采用调制信号，应用门电路测量了两路输入信号的相差，计算出调制信号在光导纤维中的传输时间，从而得到光速。     

探照灯光斑移动现象的再讨论

指出用传统的"平行线"模型和光速有限来解释光斑移动现象,当将情况推广到极限时,会出现一些局限,并提出了一种新的与实际情况更符合的"同心圆"模型,由此可以解释光斑移动现象.     

Damping of light in a weakly resonant inhomogeneous medium

On the basis of an expression obtained earlier for the permittivity in the form of a series in powers of the atomic polarizability, the mechanism of damping of light caused by the processes of reemission between two atoms is considered. It is shown that, on an increase in the polarizability, as a consequence of the light frequency approaching the resonance frequency, this mechanism leads to a sharp increase in the extinction coefficient. This effect is caused by the collective behavior of the atoms and is not connected with the natural absorption near the resonance.     

迈克耳孙的光速测定实验

简述了迈克其孙的科学生涯,介绍了他从演示傅科的光束实验开始,到测出为世界公认的光速值,并测出在水和二硫化碳中的光速的工作,;以及在晚年仍如何坚持提高光速测量精度;强调了克耳孙热爱实验,尊重实验,善于在改进中创新,在工作中坚持高标准的优良作风。     

Hysteresis phenomena in the light self-diffraction in a dense resonant medium

On the basis of the modified Bloch equations a theory is developed of the light self-diffraction in a thin film of a dense resonant medium with allowance for the dipole-dipole interactions of atoms. It is shown that for certain values of intensity of an external field, there occurs in the film the light-induced first-kind phase transition which causes the emergence of regions (domains) with the high excitation of atoms. The switching effects of the system dense resonant medium + periodically-modulated field under consideration result in a hysteresis behaviour in the dependence of the diffraction efficiency on the adiabatically changing intensity of the external field. The predicted hysteresis offers additional potentialities in the investigation of the dynamics of the first-kind phase transition in dense media and outlook for usage of the film as a switching logical element.