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1.
The nonlocal nonlinearity stemming from molecular reorientation in nematic liquid crystals supports the formation of multiple solitary waves, following the onset of spatial modulational instability from both wide and focused input beams. We report experimental observations of such phenomena at power levels of hundreds of milliwatts in planar cells with a voltage bias. 相似文献
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The influence of the ultrasonic wave on the dynamic diffraction of the Mössbauer γ quanta in the perfect Si crystals has been studied. Both the scattering intensities and the diffractional Mössbauer spectra for different reflections and ultrasonic frequencesν s have been measured. Some unusual results such as the enhancement of the elastic scattering at highν s with ultrasound amplitude growing and non-exponential decrease of the Debye-Waller factor (connected with ultrasonic phonons) at lowν s have been obtained. The experimental data are in good agreement with the theoretical calculations. 相似文献
3.
G. V. Kulak 《Technical Physics》1997,42(9):1055-1057
An intermediate regime for the diffraction of light on ultrasound in gyrotropic anisotropic and cubic crystals in an external
electric field is considered. A system of equations of the coupled waves, which describes acoustooptic diffraction in gyrotropic
anisotropic crystals with consideration of the electrically induced optical anisotropy for a strong interaction between light
and ultrasound, is presented. An intermediate regime for the diffraction of light on ultrasound in gyrotropic anisotropic
crystals which is close to the Bragg regime for a weak acoustooptic interaction is studied. It is shown that the diffracted
light is elliptically polarized and that the ellipticity and polarization azimuth of the diffracted wave depend on the anisotropy
of the photoelasticity, the electrically induced anisotropy of the crystal in the external electric field, the gyrotropy,
and the asymmetry of the diffraction structure.
Zh. Tekh. Fiz. 67, 80–82 (September 1997) 相似文献
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R. S. Akopyan A. V. Galstyan G. G. Zakharyan N. F. Vardanyan Yu. S. Chilingaryan 《Technical Physics》2006,51(6):752-757
The diffraction and polarization properties of thick anisotropic holographic gratings recorded in polymer-dispersed liquid crystals are studied experimentally and theoretically. Such gratings are anisotropic and sensitive to temperature variations and also exhibit a strong dependence of the diffraction properties on the incident radiation polarization because of the presence of liquid-crystal molecules. The dependences of the diffraction efficiency and diffracted beam polarization orientation on the diffraction grating temperature and incident beam linear polarization are obtained for the case of Bragg incidence. The same dependences are derived using the known experimental temperature curves of the liquid crystal permittivity. The experimental data are in agreement with the theoretical calculations. The feasibility of controlling the diffraction characteristics of the grating in a wide temperature interval is demonstrated. 相似文献
6.
V. I. Balakshii V. B. Voloshinov G. A. Knyazev L. A. Kulakova 《Technical Physics》2008,53(10):1336-1343
The optical, acoustic, and acoustooptic properties of tellurium crystals viewed as a candidate material for mid-and far-IR
acoustooptic devices are considered. The phase velocities, polarization, and drift angles of the acoustic energy in different
crystal planes are calculated. The acoustooptic figure of merit for tellurium under the anisotropic diffraction conditions
is estimated, and light-sound interaction geometries promising for acoustooptic applications are discussed. Measuring data
for the optical and acoustooptic parameters of tellurium crystals are given. 相似文献
7.
E. F. Martynovich 《Russian Physics Journal》2000,43(3):193-204
The spatial-temporal dynamics of the photochemical conversion of color centers with varying multipolarity and orientation
of quantum transitions in irradiated anisotropic crystals exposed to pulsed polarized femtosecond optical radiation and the
resulting spatial distribution of the residual and newly-formed color centers are studied. The properties of the concurrent
luminscence and photoconductive processes closely related to the photochemical transformation of light-absorbing quantum systems
are also examined. A femtosecond laser technique is proposed, which allows extended spatial-periodic structures or narrow
profiles of color-center concentrations, including single thin layers or dips, to be formed at a specified depth from the
crystal surface through photochemical transformations.
Institute of Applied Physics at the Irkutsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No.
3, pp. 31–42, March, 2000. 相似文献
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We propose a novel all-optical, nonlinear mode-conversion scheme based on cascaded three-wave-mixing phase-matched interactions in quadratic nonlinear crystals. We demonstrate the method experimentally by performing all-optical mode conversion of an input 1636 nm Hermite-Gaussian mode from the zeroth order to the first order using two periodically poled LiNbO(3) crystals. Nonlinear mode conversion of an input beam into a higher order, orthogonally polarized output beam can be realized using only one quasiperiodic nonlinear structure. Moreover, it can be enhanced for conversion of complex modes, e.g., Laguerre-Gaussian or Bessel modes. 相似文献
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O. V. Borovkova V. E. Lobanov A. K. Sukhorukova D. A. Chuprakov A. P. Sukhorukov 《Moscow University Physics Bulletin》2008,63(6):430-432
The features of anisotropic discrete diffraction in a cascade-induced lattice formed by two crossed pump waves in a quadratically nonlinear medium have been studied. The transition from the diffraction of a signal beam in free space to discrete diffraction with the further capture in a waveguide in a defocusing lattice by the increasing of the pump wave intensity has been traced. 相似文献
12.
W. Eckhardt 《Optics Communications》1978,27(3):299-302
Landau and Lifschitz's theory of electromagnetic (EM) fluctuations in dielectric media is applied to anisotropic dielectric crystals. In the limit of zero damping the spectra of the autocorrelation functions of the EM-field in unaxial crystals are calculated. With the aid of these spectra a generalized Planck's law of radiation is reported. 相似文献
13.
We discuss the nature of a new type of surface polariton which occurs on anisotropic media, involving a photon coupled to a surface virtual excitation. Dispersion curves are calculated for α-quartz, where both real excitation type and virtual excitation type surface polaritons are predicted. The dispersion curves for virtual excitation surface polaritons are found to remain at small wavevector, and the endpoints of the dispersion curves terminate on the bulk polariton dispersion curves in the two media. The virtual excitation surface polaritons which occur on gyromagnetic and gyrodielectric media are also noted. 相似文献
14.
We show that the fast Fourier transform (FFT) technique provides a computationally efficient method of calculating 2D amplitude and phase images of complex wave fields generated and measured in elastically anisotropic solids by phase sensitive acoustic microscopy. Further, we discuss how this technique can be used to treat inverse problems such as source reconstruction, image quality assessment, and the determination of elastic constants. 相似文献
15.
C. Z. Tan 《Applied physics. B, Lasers and optics》2005,80(7):875-880
The electric field of incident light induces dipoles in anisotropic media, vibrating in two perpendicular directions of the principal axes. Because of the tensor property of the dielectric constant, an induced dipole is subject to a torque, tending to rotate it about the axis parallel to the propagation direction. The directions of eigenvibration of the ordinary (o-ray) and extraordinary (e-ray) waves are no longer perpendicular in this sense. We propose here the relationships to describe the rotation of the induced dipole in the perpendicular electric fields. The rotation angles are found to increase with increasing dielectric constants and electric field strength of the incident light, exhibiting large values near the resonance frequencies in the infrared range at the azimuth angle /4 of the polarized incident light. Piezoelectric and ferroelectric crystals have a large value of the dielectric constant in the infrared frequency range. Rotations of the vibration direction of the o-ray and the e-ray waves are shown in the infrared transmission spectra recorded by incidence of the polarized light and transmission through piezoelectric and ferroelectric crystals (-quartz, LiNbO3, and LiTaO3). Interference of the o-ray and the e-ray waves transmitted through the crystals confirms the rotations of the vibration directions, a self-modulation effect of light in piezoelectric and ferroelectric crystals induced by the electric field of the propagating light. 相似文献
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《Superlattices and Microstructures》1999,25(1-2):343-346
Photonic crystals are very promising because they provide the ability to create high performance microcavities with a high quality factor for a small modal volume. These cavity modes are obtained by creating defects in the periodicity and the defect design must be optimized to obtain the highest transmission. We investigate defect properties in the graphite structure by varying the size of some cylinders. Using the Transfer Matrix Method, we calculate the in-plane diffraction of defect rows and show how this diffraction affects the transmission of the cavity mode. 相似文献
18.
We extend the work of Thirukkanesh and Maharaj (Class Quantum Gravity 25:235001, 2007) by considering quadratic equation of state for the matter distribution to study the general situation of a compact relativistic
body. Presence of electromagnetic field and anisotropy in the pressure are also assumed. Some new classes of static spherically
symmetrical models of relativistic stars are obtained. All the results given in Thirukkanesh and Maharaj (Class Quantum Gravity
25:235001, 2007) and there in can also be recovered as a particular case of our work. 相似文献
19.
In the case of cubic ionic crystals Havinga has shown that the temperature variation of dielectric constant could be described
in terms of volume and temperature effects. By extending his formalism to anisotropic, ionic crystals it has been shown that
unlike in cubic ionic crystals where the volume effect consists of a change in the number per unit volume of the polarizable
particles and their polarizability with volume, in the case of anisotropic ionic crystals, in addition to these, a variation
in the anisotropy of polarizability due to uneven thermal expansion also has to be taken into account. This method of analysis
has been examined by taking rutile as an example. 相似文献
20.
Combination of quasi-isotropic approximation (QIA) of geometric optics with paraxial complex geometric optics (PCGO) is suggested, which allows describing both diffraction and polarization evolution of Gaussian electromagnetic beams in weakly anisotropic inhomogeneous media. Combination QIA/PCGO reduces Maxwell equations to the system of the ordinary differential equations of the first order and radically simplifies solution of various problems, related to microwave plasma diagnostics, including plasma polarimetry, interferometry and refractometry in thermonuclear reactors. Efficiency of the method is demonstrated by the example of electromagnetic beam diffraction in a linear layer of magnetized plasma with parameters, modeling tokamak plasma in the project ITER. 相似文献