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11.
Wentao Jin 《Optics Communications》2011,284(24):5814-5817
We fabricate three-dimensional nonlinear photonic lattices in iron-doped lithium niobate photorefractive crystal for the first time by a single amplitude mask. The experimental setup of this method is very simple and flexible. The period of the lattices can be dominated easily. We analyze the three-dimensional photonic lattices by plane wave guiding and far field diffraction pattern imaging. The induced photonic lattices can exist stably for a long time in the photorefractive crystal. 相似文献
12.
For a nonlinear medium, a given incident laser beam may produce different transmitted light waves. This phenomenon (the so-called optical bistability) corresponds to multiple solutions of the boundary value problems of the nonlinear Helmholtz equation. Optical bistability can be useful in the design of optical switches. Devices that display this behavior could potentially play a major role in the development of optical communication systems and computing. In this article we present experimental results concerning the optical bistability in photorefractive BaTiO3:Fe crystal. Two laser beams were used to interact with the photorefractive crystal which resulted in the bistability of the intensity of transmitted wave. This was achieved without the application of any optical resonator. High contrast optical bistability is found experimentally in the pump-ratio dependence of the output intensity. 相似文献
13.
An optical technique for slope detection by using as storing medium a photorefractive BSO crystal is proposed. The technique relays in that a local tilt produced in a diffusing reflective surface can be mapped as a speckle transversal shifting in a plane perpendicular to the optical axis. The volume nature of the storing medium is quite adequate to highlight the speckle volume nature and its associated properties. Experimental results obtained by using a rubber vibrating membrane are presented. 相似文献
14.
In this work, the improvement of the dynamic range of a micro displacement sensor based on fiber specklegrams holographically stored in a photorefractive BSO (Bi12SiO20) crystal is reported. In our experimental setup, a plastic optical fiber (POF) was used to generate a subjective speckle pattern that was recorded in the crystal using a two-wave mixing arrangement. The speckle size was controlled by modifying the diameter of a pupil aperture adjacent to a lens producing the image of the speckle. Fringe patterns were obtained at the output of the system by producing micro displacements of the fiber output end. An increase in the visibility of the fringe patterns was appreciated when the pupil aperture diameter decreased even without controlling the average modulation of the intensity of the light pattern, i.e. when the speckle length increased and the average light modulation simultaneously decreased. This behavior allowed recovering the autocorrelation functions of fringe patterns associated with displacements that initially led to decorrelation, and therefore, significantly to improve the dynamic range of the metrological system. To the best of our knowledge this is the first report about the influence of speckle size on the dynamic range of fiber specklegrams sensors recorded on photorefractive materials. 相似文献
15.
16.
We investigate theoretically the temperature effects on the evolution and stability of a separate holographic–Hamiltonian dark–dark or bright–dark soliton pair formed in an unbiased serial photorefractive crystal circuit. Our numerical results show that, for a stable dark–dark or bright–dark soliton pair originally formed in a crystal circuit at given temperatures, when the crystal in which formed a Hamiltonian dark soliton changes, the holographic dark or bright soliton supported by the other crystal tends to evolve into another stable soliton or experiences larger cycles of compression or breaks up into beam filaments or exhibit a common decaying process. The holographic dark soliton is more sensitive to the temperature change than the holographic bright one. 相似文献
17.
J. D. Shakos A. M. Cox D. P. West K. S. West F. A. Wade T. A. King R. D. Blackburn 《Optics Communications》1998,150(1-6):230-234
The processes limiting the rate of response of highly diffractive, reorientationally enhanced photorefractive polymer composite materials are identified from a series of degenerate four wave mixing and Mach–Zehnder interferometric measurements. In the regime of low intensity writing beams charge generation limits the rate of holographic grating formation, but at higher intensities charge transport or reorientation of dye molecules can restrict the rate of grating formation more strongly. A grating risetime of 540 ms is observed in a composite of high dye content with high reorientational mobility of the dye molecules. In this case it is proposed that the charge carrier mobility of the doped poly(N-vinylcarbazole):2,4,7-trinitro-9-fluorenone (PVK:TNF) matrix is the principal limiting factor in grating response rates. 相似文献
18.
The photorefractive planar lens for converting a vertical incident plane wave to a lateral-spread spherical wave and vice versa, is suggested. Using the two-beam coupled-wave theory, the coupled wave equations are derived and their half-analytical solutions are also given in terms of an infinite series. The diffraction properties (beam profiles, diffraction efficiency) of the local volume grating in the lens are presented. And the focusing property of the lens is discussed and compared with that of an ideal convergent spherical wave. It is demonstrated that the suggested photorefractive planar lens shows a good focusing effect. 相似文献
19.
光折变晶体多重存储中,为获得均匀的衍射效率,要根据记录晶体的时间常数计算相继写入全息图的曝光时间,而晶体的时间常数是记录光强的幂函数.本文分析了光强变化对衍射效率的影响.结果表明,对曝光时间加以适当修正,可补偿光强变化对衍射效率均匀性的影响. 相似文献
20.
An impurity mediated mechanism of photorefractive effect in BaTiO3 is proposed. The photoinduced changes in the relative concentration of Fe3+ in BaTiO3 results in an electro-optic coupling through a combination of the Sangster and piezoelectric effects. This is based on the
examination of the extensive results on the EPR of Fe3+ in the BaTiO3 lattice. This model explains the improved photorefractive behavior of BaTiO3 on doping with Co2+. 相似文献