B.Ya. Zel'dovich

Orientational Optical Nonlinearity of Liquid Crystals

Abstract As a result of development of optics during many centuries the concept was formed that a medium can strongly influence on the light propagation, but the light itself cannot have backward influence on the medium. That concept was refuted only with appearing of coherent and high power radiation of lasers, see, e.g., Nobel Lecture by N. Bloembergen in 1981. A new field in physics–nonlinear optics—formed as a result. The main part of laser investigations concerns with nonlinear optical phenomena, nowadays. First of all these phenomena are of extraordinary interest and beauty and provide for new methods of physical investigations. Secondly, the knowledge of laws governing the interaction of a powerful light with a medium is necessary for the correct utilization of laser beams. Finally, a great number of devices of up-to-date laser optics is totally based on utilization of nonlinear optical effects; generation of higher harmonics of light, stimulated scattering of light, optical phase conjugation, self...

X-ray and far uv multilayer mirrors: principles and possibilities.

The possibility of making multilayer reflecting coatings by using materials whose dielectric susceptibility is very near to unity at the frequency under consideration is discussed. For the pair of substances with a given Ree and Ime the explicit expressions are obtained for the value of reflection coefficient and for the optimum thickness of layers. The published data on Re and Im allowed us to choose the pairs of substances for which one may hope to create (in principle) the mirrors for normal incidence with R ~ 50% at lambda greater, similar 30 A.

Polar asymmetry of photoionization by a field with 〈E3〉 ≠ 0. Theory and experiment

Abstract We predicted and calculated the polar asymmetry of the electron angular distribution, due to the interference between one-photon ionization by a field of frequency 2ω and two-photon ionization by a field of frequency ω. The effect is observed experimentally at simultaneous illumination of a photomultiplier by picosecond Nd-laser pulses (λ = 1.06 μm) and its second harmonic radiation (λ = 0.53 μm).

Theory of a new linear magnetorefractive effect in liquids

A new linear magneto-optic effect predicted earlier by the authors is considered. The effect appears in liquids composed mainly of chiral molecules. Phenomenologically the new effect manifests itself as a change in the refractive index, which is proportional to the scalar product (B . k), where k is the photon wave vector, and B, the external quasi-static magnetic field. The constant of the new effect has been calculated. The expression obtained contains matrix elements of electric and magnetic dipoles and electric quadrupoles taken between electronic wave-functions of the molecule. A simple interpretation of the mechanism for the new effect is given. The cascade mechanism for a contribution of the first order terms to the observable constants of the second order effects is treated. In particular, the corrections to magnetostriction and Cotton-Mouton constants due to the Faraday effect are determined. It is shown that the cascade mechanism does not contribute to the observable value of the new magnetorefr...

Electrical analog of the Faraday effect and other new optical effects in liquids

Abstract A number of new optical effects in liquids is considered, including the electrical analog of the Faraday effect etc. Some of the new effects may appear only in liquids consisting of right-left-nonsymmetrical molecules and some in electrically conductive liquids only. The mechanisms of related processes are discussed and estimations of the corresponding constants are given. Most of the predicted new effects may be registered with the use of modulation of external electrical and magnetic fields and synchronous detection of the signal.

Optical phase conjugation by microwatt power of reference waves via liquid crystal light valve

Abstract The operation of an LC light valve with a planarly orientated nematic cell with photosensible semiconductor layer is discussed using S-deformation near Frederiksz transition. Optical phase conjugation (OPC) of He-Cd laser radiation (λ=441.6 nm) with microwatt power is suggested and performed experimentally by the incident reference wave power P 1 ⩾10 -5 W. The diffraction efficiency of the hologram-valve in the direction of OPC-wave was ∼0.06 and the OPC fraction in reflected radiation was about 30–40%, the total nonlinear reflection factor being ∼10 -2 .

The orientational mechanism of nonlinearity and the self-focusing of He-Ne laser radiation in nematic liquid crystal mesophase (theory and experiment)

A giant optical nonlinearity of self-focusing type in the oriented mesophase of nematic liquid crystals (NLC) due to the director reorientation under the action of a light wave field is predicted. Self-focusing of He-Ne laser radiation with power ∼10-2 W and power density ∼50 W/cm2 in a planar oriented 60 μm thick NLC layer has been carried out experimentally. The measured value of the nonlinearity effective constant e 2 = 0.07 cm3/erg corresponds to theoretical predictions, and turns out to be larger than the CS2 nonlinearity by ≈ 109 times.

The Orientational Optical Non-linearity of Liquid Crystals. I. Nematics

Abstract The optical non-linearity of a nematic liquid crystal (NLC) is considered. The strongest effect studied is due to the local turn of NLC director. The possibility of wavefront conjugation by four-wave interaction in a NLC is considered. Strong effects of self-focusing in a NLC due to the orientational mechanism of non-linearity are predicted.

Separation of mirror isomeric molecules by radio-frequency electric field of rotating polarization

Abstract We predict the effect of separation of mirror isomeric molecules into right and left fractions from a racemic liquid solution under the action of a radio-frequency electric field of rotating polarization. An approximate calculation of the dependence of the separation rate on the field frequency is given. Numerical estimations show the possibility of experimental observation of the effect.

SBS wave front reversal for the depolarized light — Theory and experiment

Theoretical results concerning the wave front reversal (WFR) of spatially depolarized light in stimulated scattering are presented. The modes of scattering medium are found and the deterioration of reversal quality for the depolarized light is predicted. Experimental investigation of WFR in backward stimulated Brillouin scattering (SBS) in acetone was carried out when the light beam with λ = 1.06 μm was depolarized by the etched calcite plate. The share of scattered energy which has exactly reversed configuration, was measured. Experimental results quantitatively coincide with the theoretical conclusions.