共查询到20条相似文献,搜索用时 0 毫秒
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In a disordered nonlinear medium the transmitted speckle pattern was predicted to become unstable as a result of the positive feedback between intensity fluctuations and local variations of the refractive index. We show experimental evidence of speckle instability for light transversally scattered in a liquid crystal cell, where a two-dimensional controlled disorder is imprinted by suitable illumination of a photoconductive wall and nonlinearity is obtained through optical reorientation of the liquid crystal molecules. The speckle pattern spontaneously oscillates at discrete frequencies above a critical threshold, whose dependence on the scattering mean free path confirms the crucial role of disorder in the feedback process. 相似文献
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Propagation of two orthogonally polarized time-delayed optical solitons in low-birefringence optical fiber is studied experimentally. We demonstrate soliton trapping and collisions and also the ability to control the separation and shape of soliton pulses by varying the power at the input of the fiber. 相似文献
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On the basis of simple physical arguments involving energy flows and power invariants, we show that nonparaxiality stabilizes (1+2D) soliton beams in Kerr media. 相似文献
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A theoretical analysis of vectorial three-wave mixing in isotropic Kerr media is presented. The analysis based on the coupled-wave equations describes the amplification of a weak wave by coupling with a strong pump wave phase matched by optically induced change of average refractive index. The phase matching condition for interacting waves with different polarizations is calculated, allowing a large amplification of a weak wave by three-wave mixing in thick Kerr media. The main conclusions of our theoretical analysis are supported by the results of experiments in CS2 liquid medium. 相似文献
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A bound state of temporal solitons in optical fibers is predicted numerically and demonstrated experimentally. It is appropriately described as a pair of bright solitons, bound together by a dark soliton. This structure exists only in dispersion-managed fiber and is different from bound solitons in fiber lasers. 相似文献
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G. B. Altshuller V. S. Ermolaev V. B. Karassev S. A. Kozlov K. I. Krylov L. I. Pavlov 《Applied physics. B, Lasers and optics》1983,32(2):97-100
Nonlinear reflection of elliptically polarized light waves from the interface of two isotropic transparent media, is investigated for the first time. Nonlinear Fresnel formulae are obtained. It is shown, that when linear refractive indices are equalized, selfdeformation of the polarization ellipse in nonlinear reflection depends only on incident light ellipticity, not upon its intensity and the angle of incidence. 相似文献
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E. V. Baklanov 《Laser Physics》2008,18(9):1106-1110
The field of an elliptically polarized wave is represented for the convenient solution of practical problems. The wave amplitude is written in terms of four parameters: magnitude E, phase φ, angle ψ of the polarization plane, and ellipticity ? (|?| is the ratio of the ellipse axes). The shortened equations are derived using these parameters and the solution of the shortened equations is obtained for a linear medium. 相似文献
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We investigate the incoherently and strongly coupled Manakov vector dipole soliton pairs in nonlocal nonlinear media. We use variational approach, to describe analytical properties of these solutions in a strongly nonlocal regime. We show that the presence of fundamental component improve stability of the dipole nonlocal soliton. In the limit of highly nonlocal nonlinearity, the evolution behaviors of the vector solitons is determined by their total power. 相似文献
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We propose a simple and effective way of creating pure dark superposition states. The generation of pure states is carried out by using bichromatic radiation with controllable polarization ellipticity. We experimentally confirm analytic formulas for polarization ellipticity to obtain m-m pure dark states in the system of Zeeman sublevels of alkali atoms. For 87Rb we experimentally accumulated 60% of the atoms in the 0-0 dark state and 50% into the (+/-1) - (+/-1) dark states. 相似文献
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Experimental observation and numerical results concerning collisions between scalar and vector spatial solitons in a Kerr planar waveguide are presented. It is shown that this configuration allows for the full control of spatial and polarization dynamics of the interacting vector solitons. On the one hand, the ability to achieve polarization control of a single-hump vector soliton is demonstrated. On the other hand, the effect of collision on the spatial symmetry-breaking dynamics of multimode vector solitons is investigated. 相似文献
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The self-action of elliptically polarized Gaussian laser pulses in an isotropic gyrotropic medium with an anomalous frequency
dispersion and cubic Kerr nonlinearity with a finite relaxation time on the order of the pulse duration is numerically studied.
It is shown that, at the output of the medium, the pulse polarization nonmonotonically varies with time. The main peak of
the pulse is additionally delayed compared to the time of passing the linear medium; the value of this delay significantly
depends on the polarization of the incident pulse and achieves a maximum for incident pulses whose degree of ellipticity is
equal to the ratio of the material constants characterizing the local and nonlocal nonlinear optical response of the medium.
It seems promising to search for possible differences in relaxation times depending on the intensity of additions to the refractive
indices of the right and left circularly polarized waves by investigating the time dependence of polarization characteristics
at the output of the medium. 相似文献
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Analytical and numerical investigation of the propagation of optical beams in Kerr-like saturable photorefractive media is carried out, utilizing a novel model for the local isotropic part of the space-charge field generated in the medium. Using a variational technique, optimal propagation parameters for the most stable propagation of otherwise unstable single Gaussian, single vortex, and optical soliton cluster beams are determined. Analogy between a ring of identical weakly overlapping solitons and a vortex of the same topological charge is explored. 相似文献
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Transverse instabilities are shown to accompany counterpropagation of optical beams through reflection gratings in Kerr media. The instability threshold of continuous waves is analytically derived, and it is shown that the presence of the grating broadens and narrows the stability region of plane waves in focusing and defocusing media, respectively. Furthermore, counterpropagating soliton stability is numerically investigated and compared with the transverse modulation instability analysis, revealing an underlying physical link. 相似文献
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Numerical methods are used to study the effect of local and nonlocal nonlinear optical susceptibilities on the parameters of a soliton whose degree of ellipticity depends on time and that is formed at a distance of several dispersion lengths in a medium with the anomalous frequency dispersion. The rotation angle of the major axis of the polarization ellipse does not depend on time and linearly increases with an increasing propagation coordinate. If the tensor components of the local nonlinear susceptibility have opposite signs, the incident elliptically polarized pulse can propagate in the regime that involves the pulse splitting into components for which the absolute values of the electric-field degrees of ellipticity are close to unity. In this case, the electric-field vector at the center of the pulse rotates in the opposite direction with respect to the rotation at the edges. 相似文献
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We theoretically demonstrate a scheme to efficiently generate attosecond pulses with high ellipticity by a counter-rotating bicircular field with frequency ratio of 1 : 3 (800 + 267 nm) and 1 : 4 (1600 + 400 nm). It is shown that efficient attosecond pulses with high ellipticity of 0.54 (800 + 267 nm) and 0.79 (1600 + 400nm) can be generated. We also investigate the scaling law of high harmonic generation yield. It is shown that the intensity of the high harmonics can be increased by more than one order of magnitude in the bicircular fields with higher frequency ratios. The high ellipticity and high efficiency of high harmonics are explained by analyzing the symmetry of driving field and the classical electron trajectories. 相似文献
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We theoretically investigate the contribution of the excited state to the ellipticity of the harmonics from H+ at different orientation angles irradiated by a linearly polarized laser pulse. It is found that the first excited state has a significant influence to the ellipticity of the harmonics, and the contribution of higher excited states to the ellipticity can be neglected. Moreover, the conclusion is not dependent on the laser intensity. 相似文献