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Diffraction efficiency
About: Diffraction efficiency is a research topic. Over the lifetime, 10320 publications have been published within this topic receiving 158298 citations.
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TL;DR: A chemical-diffusive model that, taking into account sample temperature and intensity of the curing radiation, indicates the best conditions to fabricate holographic gratings, and a Kogelnik-like model that accounts for the dependence of the diffraction efficiency on material parameters, sample temperature, and applied electric field are reviewed.
Abstract: POLICRYPS, an acronym of POlymer LIquid CRYstal Polymer Slices, is a structure made of perfectly aligned liquid crystal films separated by slices of almost pure polymer. Under suitable experimental and geometrical conditions, the structure is obtained by curing a homogeneous syrup of liquid crystal, monomer and curing agent molecules with a spatially modulated pattern of ultraviolet (UV) radiation. From an optical point of view, POLICRYPS is a holographic diffraction grating with a spatial periodicity that can be easily made of sub-micrometric scale, exhibiting diffraction efficiency values as high as 98%. Depending on the used geometry, the POLICRYPS grating can be utilized both in transmission or reflection, with negligible scattering losses, and can be switched ON and OFF by application of an external electric field of the order of few V//spl mu/m. In this paper, we review: 1) the "recipe" to fabricate POLICRYPS holographic gratings, along with their main optical and electro-optical properties; 2) a chemical-diffusive model that, taking into account sample temperature and intensity of the curing radiation, indicates the best conditions to fabricate these gratings; 3) a Kogelnik-like model that accounts for the dependence of the diffraction efficiency on material parameters, sample temperature, and applied electric field. Finally, we discuss the possibility of utilizing a micrometric sized POLICRYPS grating as a Grating Electro-Optical Pixel for high resolution display application.
71 citations
TL;DR: In this paper, permanent holographic gratings were fabricated in bulk azodye-doped polymethylmethacrylate by the coherent field of a femtosecond laser.
Abstract: Permanent holographic gratings were fabricated in bulk azodye-doped polymethylmethacrylate by the coherent field of a femtosecond laser. Optical microscopy and atomic force microscopy observations revealed that the gratings consist of two parts, surface relief gratings on both surfaces and refractive index modulated volume gratings in the interior of the polymers. The diffraction efficiency of the first-order Bragg for the gratings was estimated to be 90%.
71 citations
TL;DR: A novel digital holographic algorithm, correcting optical system imaging, is developed that uses plane wave spectrum decomposition of optical field for solving diffraction problem between parallel and tilted planes and enabling correction of imaging system aberrations.
Abstract: In the paper the optical diffraction tomographic system for reconstruction of the internal refractive index distribution in optical fiber utilizing grating Mach-Zehnder interferometer configuration is explored. The setup applies afocal imaging. Conventional grating application gives, however, highly aberrated object beam producing incorrect refractive-index reconstructions. The grating inherent aberrations are characterized, its influence on both image projections and refractive index reconstructions is presented. To remove aberrations and enable tomographic reconstruction a novel digital holographic algorithm, correcting optical system imaging, is developed. The algorithm uses plane wave spectrum decomposition of optical field for solving diffraction problem between parallel and tilted planes and enabling correction of imaging system aberrations. The algorithm concept was successfully proved in simulations and the experiment.
71 citations
TL;DR: Second order diffraction has been observed from Bragg gratings written within germanosilicate glass fibres as discussed by the authors, which is consistent with a saturation in the photo-induced change in refractive index.
71 citations
TL;DR: A new type of holographic optical element combines some of the flexibility of computer-generated holograms with the high light efficiency of volume phase holograms to produce optical elements capable of arbitrary illumination transformations with nearly 100% light efficiency.
Abstract: A new type of holographic optical element combines some of the flexibility of computer-generated holograms with the high light efficiency of volume phase holograms to produce optical elements capable of arbitrary illumination transformations with nearly 100% light efficiency. The optical element is recorded by subdividing a volume hologram film surface into numerous small areas (facets), each of which is individually exposed. A final optical system consisting of two dichromated gelatin holograms in series is demonstrated. The first hologram spatially redistributes the incident light, and the second hologram produces a desired phase front on the redistributed light.
71 citations