共查询到20条相似文献,搜索用时 15 毫秒
1.
The possibility of non-reciprocal effects developing in a ring laser with a cavity that includes spatially inhomogeneous, nonlinear elements is analyzed. The occurrence of non-reciprocal effects in intracavity generation of the second harmonic and stimulated Raman scattering is considered. 相似文献
2.
A. F. Bunkin V. G. Mikhalevich S. M. Pershin V. N. Streltsov 《Journal of Experimental and Theoretical Physics》2011,113(2):207-212
Mandelstam-Brillouin (MB) steady-state scattering in an elastic medium with a dense local zone inhomogeneity is considered
in the 1D approximation. It is shown that for a certain size of inhomogeneity, the scattered radiation spectrum contains individual
resonances whose frequencies depend on the elastic properties of microscopic inclusions. Experiments were performed using
coherent four-photon scattering spectroscopy in the range 0–1 cm−1 with a resolution of 0.06 cm−1 in specially processed distilled water and in an aqueous solution of α-chymotrypsin albumin. In both media, the presence
of MB resonances displaced is detected relative to the water resonance (≈0.25 cm−1) in different directions and corresponding to different types of microinclusions. 相似文献
3.
In this paper, we present solutions for the nonlinear Schrödinger (NLS) equation with spatially inhomogeneous nonlinearities describing propagation of light in nonlinear media, under two sets of transverse modulation forms of inhomogeneous nonlinearity. The bright soliton solution and Gaussian solution have been obtained for one set of inhomogeneous nonlinearity modulation. For the other, bright soliton solution, black soliton solution and the train solution have been presented. Stability of the solutions has been determined by exact soliton solutions under certain conditions. 相似文献
4.
Parametric scattering of two copropagating coherent light waves into cones of light with the same polarization is considered both experimentally (in photo-refractive LiNbO3:Fe) and theoretically. 相似文献
5.
A considerable distinction of light-induced scattering in optically biaxial crystals comes from the fact that the principal axes of the optical indicatrix do not coincide with the crystallographic directions. The study of photorefractive scattering in Sn2P2S6 (monoclinic symmetry) revealed the particular requirements as to light polarization for excitation of parametric scattering and the polarization inhomogeneity of wide-angle scattering. 相似文献
6.
S. G. Romanov 《JETP Letters》2004,79(12):614-619
Spectra of light losses are studied at a fixed angle of incidence of a collimated beam on the surface of an opal anisotropic photon crystal at various observation angles. It is shown that the structure of the forward-and backscattered light spectra is connected with the existence of several directional photonic forbidden bands. It is demonstrated that back scattering is enhanced and forward scattering is suppressed in the frequency region of photonic forbidden bands. It is suggested that a scattering band associated with photon localization at the photonic gap edge is observed. 相似文献
7.
The (2+1)-dimensional nonlinear SchrSdinger (NLS) equation with spatially inhomogeneous nonlinearities is investigated, which describes propagation of light in (2+1)-dimensional nonlinear optical media with inhomogeneous nonlinearities. New types of optical modes and nonlinear effects in optical media are presented numerically. The results reveal that the regular split of beam can be obtained in (2+1)-dimensional nonlinear optical media with inhomogeneous nonlinearities, by adjusting the guiding parameter. Furthermore, the stability of beam regular split is discussed numerically, and the results reveal that the beam regular split is stable to the finite initial perturbations. 相似文献
8.
The(2 1)-dimensional nonlinear Schr(o)dinger(NLS)equation with spatially inhomogeneous nonlinearities is investigated,which describes propagation of light in(2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities.New types of optical modes and nonlinear effects in optical media are presented numerically.The results reveal that the regular split of beam can be obtained in (2 1)-dimensional nonlinear optical media with inhomogeneous nonlinearities,by adjusting the guiding parameter.Furthermore,the stability of beam regular split is discussed numerically,and the results reveal that the beam regular split is stable to the finite initial perturbations. 相似文献
9.
10.
H. C. Guo X. H. Zhang S. H. Tang Y. Q. Qin Y. Y. Zhu 《Applied physics. B, Lasers and optics》2010,98(2-3):253-259
With the nonlinear diffraction concept, we present a diffractive study of optical parametric interactions in nonlinear photonic crystals. The nonlinear diffraction concept enables the design of complicated nonlinear photonic crystal structures in an intuitive way. We show that there are two basic linear sequences, the anti-stacking and the para-stacking sequences, existing in a one-dimensional structure; and we present the realization of multiple phase-matching resonances in the combination of the two basic sequences. The parameters affecting the structure factor of a two-dimensional nonlinear photonic crystal are investigated, which indicate that not only the Ewald construction but also the relative domain size determines two-dimensional nonlinear diffractions. 相似文献
11.
Light scattering and reflection measurements using attenuated total reflection technique for s polarization of the incident light on a finite one-dimensional photonic crystal are reported. Angular specular reflection was measured experimentally to determine, the optimum thickness, the angular position of the surface mode, and the number of bi-layers of the system. It was demonstrated that the position of the surface mode inside the last film is close to the asymptotic value when the number of periods is increased. Spectral reflection measurements were made to determine experimentally the band gap width and measure the dispersion relation of the surface mode inside this band. The corresponding field amplitude was calculated (∣E∣2) showing that in resonant conditions it has a maximum near the surface. The angular dependence of the scattered light measured displays a peak caused by singles cattering and located approximately at the excitation angle of the surface electromagnetic mode. When the incident light is in resonance with the surface electromagnetic wave, it is found experimentally that the scattering of light is enhanced overall by approximately one order of magnitude in comparison with the off-resonance case. 相似文献
12.
A new structure based on a semi-circular photonic crystal is proposed to achieve asymmetric light propagation. The semi-circular photonic crystal structure proposed in this paper is a deformation of a two-dimensional conventional square photonic crystal. Through the directional bandgap of the semi-circular photonic crystal, the light from one direction can transfer to the other side, but the light from the opposite direction cannot. A high contrast ratio is obtained by designing the constitutive parameters of the photonic crystal and choosing the suitable light frequency. This structure promises a significant potential in optical integration and other areas. 相似文献
13.
V. N. Bogomolov L. S. Parfen’eva I. A. Smirnov H. Misiorek A. Jzowski 《Physics of the Solid State》2002,44(1):181-185
The thermal conductivity κ of photonic crystals differing in degree of optical homogeneity (single crystals of synthetic opals) was measured in the 4.2–300 K temperature range. The thermal conductivity revealed, in addition to the conventional decrease in comparison with solid amorphous SiO2 characteristic of porous solids, a noticeable decrease for T<20 K, the range wherein the phonon wavelength in amorphous SiO2 approaches the diameters of the contact areas between the opal spheres. This effect is enhanced in the case of phonon propagation along the SiO2 sphere chains (six directions in the cubic opal lattice). The propagation of light waves (photons) through a medium with spatially modulated optical properties (photonic crystals) is presently well studied. The propagation of acoustic waves through a medium with spatially modulated acoustic properties (phononic crystals) may also reveal specific effects, which are discussed in this paper; among them are, e.g., the ballistic mode of phonon propagation and waveguide effects. 相似文献
14.
Alfven-wave scattering by inhomogeneities of the permittivity tensor (r) is examined. The scattering index , phase velocity v*, and group velocity c* are calculated over the entire wavelength range. Asymptotic formulas for , v*, and c* are derived for long (as compared with scatterer size), short, and ultrashort wavelengths.Moscow Institute of Electronic Engineering. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 5, pp. 421–432, May, 1992. 相似文献
15.
用时域有限差分法研究了电磁波在等离子体光子晶体中的传播特性。数值模拟中使用完全匹配层吸收边界条件,计算了电磁波通过等离子体光子晶体的反射和透射系数。讨论了等离子体密度、等离子体温度、介电常数比和引入缺陷层对等离子体光子晶体光子带隙的影响。 相似文献
16.
Slow light in photonic crystals 总被引:3,自引:0,他引:3
The problem of slowing down light by orders of magnitude has been extensively discussed in the literature. Such a possibility can be useful in a variety of optical and microwave applications. Many qualitatively different approaches have been explored. Here we discuss how this goal can be achieved in linear dispersive media, such as photonic crystals. The existence of slowly propagating electromagnetic waves in photonic crystals is quite obvious and well known. The main problem, though, has been how to convert the input radiation into the slow mode without losing a significant portion of the incident light energy to absorption, reflection, etc. We show that the so-called frozen mode regime offers a unique solution to the above problem. Under the frozen mode regime, the incident light enters the photonic crystal with little reflection and, subsequently, is completely converted into the frozen mode with huge amplitude and almost zero group velocity. The linearity of the above effect allows the slowing of light regardless of its intensity. An additional advantage of photonic crystals over other methods of slowing down light is that photonic crystals can preserve both time and space coherence of the input electromagnetic wave. 相似文献
17.
Demi L van Dongen KW Verweij MD 《The Journal of the Acoustical Society of America》2011,129(3):1221-1230
Experimental data reveals that attenuation is an important phenomenon in medical ultrasound. Attenuation is particularly important for medical applications based on nonlinear acoustics, since higher harmonics experience higher attenuation than the fundamental. Here, a method is presented to accurately solve the wave equation for nonlinear acoustic media with spatially inhomogeneous attenuation. Losses are modeled by a spatially dependent compliance relaxation function, which is included in the Westervelt equation. Introduction of absorption in the form of a causal relaxation function automatically results in the appearance of dispersion. The appearance of inhomogeneities implies the presence of a spatially inhomogeneous contrast source in the presented full-wave method leading to inclusion of forward and backward scattering. The contrast source problem is solved iteratively using a Neumann scheme, similar to the iterative nonlinear contrast source (INCS) method. The presented method is directionally independent and capable of dealing with weakly to moderately nonlinear, large scale, three-dimensional wave fields occurring in diagnostic ultrasound. Convergence of the method has been investigated and results for homogeneous, lossy, linear media show full agreement with the exact results. Moreover, the performance of the method is demonstrated through simulations involving steered and unsteered beams in nonlinear media with spatially homogeneous and inhomogeneous attenuation. 相似文献
18.
Using group-theory arguments, we demonstrate that, unlike in homogeneous media, no symmetric vortices of arbitrary order can be generated in two-dimensional (2D) nonlinear systems possessing a discrete-point symmetry. The only condition needed is that the nonlinearity term exclusively depends on the modulus of the field. In the particular case of 2D periodic systems, such as nonlinear photonic crystals or Bose-Einstein condensates in periodic potentials, it is shown that the realization of discrete symmetry forbids the existence of symmetric vortex solutions with vorticity higher than two. 相似文献
19.
We examine the spatial evolution of lightwaves in a nonlinear photonic crystal with a quadratic nonlinearity, when a second harmonic and a sum-frequency generation are simultaneously quasi-phase-matched. We find the conditions for a transition to Hamiltonian chaos for different amplitudes of lightwaves at the crystal boundary. 相似文献
20.
A model to analyze the interaction of the parametric fields being generated in a two-dimensional nonlinear photonic crystal has been developed. The analysis provides details of the interference of the generated wave(s) both inside and in the region just outside the crystal. The results are verified by second-harmonic generation in a LiNbO3 crystal that has been poled with a tetragonal inverted domain structure. 相似文献