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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: An algorithm is reported for the design of a phase-only diffractive optical element (DOE) that reshapes a beam focused using a high numerical aperture (NA) lens.
Abstract: An algorithm is reported for the design of a phase-only diffractive optical element (DOE) that reshapes a beam focused using a high numerical aperture (NA) lens. The vector diffraction integrals are used to relate the field distributions in the DOE plane and focal plane. The integrals are evaluated using the chirp-z transform and computed iteratively within the Method of Generalized Projections (MGP) to identify a solution that simultaneously satisfies the beam shaping and DOE constraints. The algorithm is applied to design a DOE that transforms a circularly apodized flat-top beam of wavelength lambda to a square irradiance pattern when focused using a 1.4-NA objective. A DOE profile is identified that generates a 50 lambda x 50 lambda square irradiance pattern having 7% uniformity error and 74.5% diffraction efficiency (fraction of focused power). The diffraction efficiency and uniformity decrease as the size of the focused profile is reduced toward the diffraction limited spot size. These observations can be understood as a manifestation of the uncertainty principle.
39 citations
TL;DR: A binary diffraction model is introduced to study the sensitivity of the wavefront phase of binary computer-generated holograms on groove depth and duty-cycle variations, and the derivation of relationships is obtained by using the Fourier method.
Abstract: A binary diffraction model is introduced to study the sensitivity of the wavefront phase of binary computer-generated holograms on groove depth and duty-cycle variations. Analytical solutions to diffraction efficiency, diffracted wavefront phase functions, and wavefront sensitivity functions are derived. The derivation of these relationships is obtained by using the Fourier method. Results from experimental data confirm the analysis. Several phase anomalies were discovered, and a simple graphical model of the complex fields is applied to explain these phenomena.
39 citations
TL;DR: An approach for fabricating widebandwidth and highly reflective Bragg grating structures with the technique of holographic photopolymerization of a liquid crystal (LC) polymer composite is presented in this paper.
Abstract: An approach for fabricating wide-bandwidth and highly reflective Bragg grating structures with the technique of holographic photopolymerization of a liquid crystal (LC) polymer composite is presented. The key to this fabrication method that distinguishes it from previous methods is the use of a nonreactive solvent, acetone, to dissolve the photoinitiator and coinitiator in an acrylate monomer/LC mixture. The addition of acetone results in the creation of controllable periodic voids inside the thin film after the acetone evaporates. Peak reflectivity as high as 80% and a broad reflection bandwidth of 80nm were observed in the reflection gratings formed with acetone present in the starting mixture. It was estimated from a fit to the experimental data that the resulting index mismatch was approximately 0.2; consistent with the presence of air voids. It is determined that tunable wavelength, diffraction efficiency, and bandwidth of reflection notches can be achieved by backfilling with fluids of different ref...
39 citations
TL;DR: An empiric equivalence rule is obtained that makes it possible to create equivalence classes of gratings that among themselves show a variety of profiles but have, as long as only two orders are propagating, efficiency curves lying very close to each other.
Abstract: By use of simple theoretical considerations on the efficiency dependence of a wide class of commercially available gratings, we obtained an empiric equivalence rule. This rule makes it possible to create equivalence classes of gratings that among themselves show a variety of profiles but have, as long as only two orders are propagating, efficiency curves lying very close to each other. The equivalence rule is visualized by drawing a nomogram. The rule and the grating nomogram serve as a basis for finding new and explaining old properties of ruled, holographic, and lamellar gratings.
39 citations
TL;DR: A theoretical model is developed that predicts achievable diffraction efficiency as a function of oxidation state, doping level, photovoltaic field, crystal length, and region of beam overlap and is compared with experimental results for achievablediffraction efficiency and erasure-time constant.
Abstract: We show that the oxidation state of Fe in LiNbO3 has two competing effects on the diffraction efficiency of multiple holograms in 90 degree-geometry holographic storage. For crystals with moderate absorption, the saturation space-charge field is larger after high-temperature reduction treatment. However, reduction also increases absorption, which reduces the overall diffraction efficiency. We develop a theoretical model that predicts achievable diffraction efficiency as a function of oxidation state, doping level, photovoltaic field, crystal length, and region of beam overlap. We compare this model with experimental results for achievable diffraction efficiency and erasure-time constant.
39 citations