Topic
Organic photorefractive materials
About: Organic photorefractive materials is a research topic. Over the lifetime, 697 publications have been published within this topic receiving 13041 citations.
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TL;DR: In this paper, the degree of modulation of a light grating in photorefractive crystals is measured by three methods and compared with the modulation of the grating of the incident light.
Abstract: In holographic experiments many photorefractive crystals show refractive-index changes much smaller than one would expect from the known electro-optic coefficients and space-charge fields. We show that degradation of the interference pattern is the origin of this effect. The degree of modulation of a light grating in photorefractive crystals is measured by three methods and compared with the modulation of the grating of the incident light. All methods, measurement of the amplitudes of fundamental and second-order gratings, of the grating amplitudes in a crystal with and without another crystal in front of it, and of the drift currents through an inhomogeneously illuminated sample, yield consistent results: In lithium niobate there is almost no degradation of the light pattern. However, in our barium titanate and potassium tantalate–niobate samples the degree of modulation is smaller, and the reduction factor is 0.55 and 0.60, respectively. Inhomogeneities of refractive-index changes are shown to be the origin of the effect.
22 citations
TL;DR: It is revealed that a TE-like full band-gap exists for materials of refractive index as low as 1.6 and the Q-factor of L3 photonic crystal nano-cavities showed a super-linear increase withRefractive index.
Abstract: We model the optical properties of L3 photonic crystal nano-cavities as a function of the photonic crystal membrane refractive index n using a guided mode expansion method. Band structure calculations revealed that a TE-like full band-gap exists for materials of refractive index as low as 1.6. The Q-factor of such cavities showed a super-linear increase with refractive index. By adjusting the relative position of the cavity side holes, the Q-factor was optimised as a function of the photonic crystal membrane refractive index n over the range 1.6 to 3.4. Q-factors in the range 3000-8000 were predicted from absorption free materials in the visible range with refractive index between 2.45 and 2.8.
22 citations
03 May 1998
TL;DR: In this paper, the number of guided modes in a waveguide induced by a bright screening soliton increases monotonically with increasing intensity ratio (the ratio between the peak soliton intensity and the background or dark irradiance).
Abstract: Summary form only given. Photorefractive spatial solitons form when the optically induced space-charge field modifies the refractive index via electro-optic effect and forms a waveguide that confines the optical beam that has induced the waveguide. Since the photorefractive response is wavelength dependent, one can generate a soliton with a weak beam and guide in it a more intense beam of a less photosensitive wavelength. Here we present theoretical and experimental studies of the waveguides induced by photorefractive screening solitons. We show that the number of guided modes in a waveguide induced by a bright screening soliton increases monotonically with increasing intensity ratio (the ratio between the peak soliton intensity and the background or dark irradiance), whereas the waveguides induced by dark screening solitons are always single-mode waveguides.
22 citations
Patent•
13 Apr 1995
TL;DR: In this article, a new class of photorefractive devices using compensating electronic and ionic gratings having relatively low efficiency but nonetheless usable gratings is provided by arranging the gratings to be reflective in a wavelength band outside the photo-excitation band of the photore-fractive material, as by using an infrared operating wavelength.
Abstract: Substantial improvements in photorefractive device lifetimes are provided by control of electron migration which results in the decay of gratings in photorefractive materials due to diffusion and other effects. A new class of photorefractive devices using compensating electronic and ionic gratings having relatively low efficiency but nonetheless usable gratings is provided by arranging the gratings to be reflective in a wavelength band outside the photo-excitation band of the photorefractive material, as by using an infrared operating wavelength. Longer lifetimes in high efficiency gratings are achieved by constant or periodic illumination of photorefractive materials to assure uniform charged distribution of electrons and maintenance of the ionic backbone grating.
22 citations
TL;DR: In this paper, photorefractive beam self-trapping is investigated in InP:Fe and is shown to occur within tens of microseconds after beam switch on, which is predicted by an analytical theoretical interpretation based on a simple photore-fraction model.
Abstract: Photorefractive beam self-trapping is investigated in InP:Fe and is shown to occur within tens of microseconds after beam switch on. This fast response time is predicted by an analytical theoretical interpretation based on a simple photorefraction model which suggests buildups in a time range consistent with experiments.
22 citations