Topic
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: In this paper, a rigorous coupled-wave analysis of diffraction by grating(s) formed in general anisotropic media is reviewed and extended, and the analysis is extended to multiple cascaded gratings and to volume-superposed gratings.
Abstract: The rigorous coupled-wave analysis of diffraction by grating(s) formed in general anisotropic media is reviewed and extended. The method is first applied to a single slanted phase and/or amplitude grating with general three-dimensional incidence of a plane wave. The regions external to the grating can be isotropic, uniaxial, or biaxial anisotropic. The cases of gratings in isotropic media and of the grating vector lying in the plane of incidence (scalar analysis) are obtained as limiting cases of this general analysis. Coupling between the two orthogonal polarizations vanishes in these limiting cases. The Bragg conditions for various combinations of ordinary (for isotropic and uniaxial) and extraordinary (for uniaxial) polarized waves are quantified. The analysis is then extended to multiple cascaded gratings and to volume-superposed gratings. Sample calculations are presented for single anisotropic gratings (a lithium niobate photorefractive hologram in air and an interdigitated-electrode-induced grating in an electro-optic crystal), for multiple cascaded gratings (a lithium niobate hologram with grating strength varying with thickness), and for superposed gratings (multiplexed hologram storage). Applications for this analysis include optical storage, switching, modulation, deflection, optical interconnects, beam splitting, beam combining, and data processing.
99 citations
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TL;DR: A highly efficient polarizing beam splitter of a deep-etched binary-phase fused-silica grating, where TE- and TM-polarized waves are mainly diffracted in the -1st and 0th orders, respectively is described.
Abstract: We described a highly efficient polarizing beam splitter (PBS) of a deep-etched binary-phase fused-silica grating, where TE- and TM-polarized waves are mainly diffracted in the −1st and 0th orders, respectively. To achieve a high extinction ratio and diffraction efficiency, the grating depth and period are optimized by using rigorous coupled-wave analysis, which can be well explained based on the modal method with effective indices of the modes for TE/TM polarization. Holographic recording technology and inductively coupled plasma etching are employed to fabricate the fused-silica PBS grating. Experimental results of diffraction efficiencies approaching 80% for a TE-polarized wave in the −1st order and more than 85% for a TM-polarized wave in the 0th order were obtained at a wavelength of 1550nm. Because of its compact structure and simple fabrication process, which is suitable for mass reproduction, a deep-etched fused-silica grating as a PBS should be a useful device for practical applications.
98 citations
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TL;DR: A simple and efficient scheme to measure OAM states (i.e. topological charge values) of vortex beams with annular gratings and shows potential large tolerance of beam alignment during the OAMStates measurement of Vortex beams.
Abstract: Measuring orbital angular momentum (OAM) states of vortex beams is of great importance in diverse applications employing OAM-carrying vortex beams. We present a simple and efficient scheme to measure OAM states (i.e. topological charge values) of vortex beams with annular gratings. The magnitude of the topological charge value is determined by the number of dark fringes after diffraction, and the sign of the topological charge value is distinguished by the orientation of the diffraction pattern. We first theoretically study the diffraction patterns using both annular amplitude and phase gratings. The annular phase grating shows almost 10-dB better diffraction efficiency compared to the annular amplitude grating. We then experimentally demonstrate the OAM states measurement of vortex beams using annular phase grating. The scheme works well even for high-order vortex beams with topological charge value as high as ± 25. We also experimentally show the evolution of diffraction patterns when slightly changing the fractional topological charge value of vortex beam from 0.1 to 1.0. In addition, the proposed scheme shows potential large tolerance of beam alignment during the OAM states measurement of vortex beams.
98 citations
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TL;DR: In this article, two types of microelectromechanical variable blaze gratings (VBGs) have been designed, modeled, fabricated, and tested, and they operate by adjusting the blaze angle of each slat so specular reflection of the incident light matches a particular grating diffraction order.
Abstract: Two types of microelectromechanical variable blaze gratings (VBGs) have been designed, modeled, fabricated, and tested. The gratings operate by adjusting the blaze angle of each slat so specular reflection of the incident light matches a particular grating diffraction order. The VBG blaze angle is adjustable with either electrostatic or thermal actuators. VBGs direct incident light in discrete directions, and are useful for steering light with beam diameters greater than 1 mm and power levels greater than 1 W. Both electrostatically and thermally actuated VBGs have been constructed from gold and polysilicon using a surface-micromachining process and tested with a 20 mW continuous wave HeNe laser operating at a wavelength of 632.8 nm. The diffraction efficiency and far-field pattern have been modeled and measured. Drive voltages for both types of gratings are measured as a function of blaze angle and selected diffraction order.
98 citations
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29 May 2002
TL;DR: In this paper, the preferential imaging of the optical train is achieved using a chromatic lens in a suitably configured imaging system, which is an example of such a lens; its focal length is inversely proportional to the X-ray wavelength.
Abstract: An element-specific imaging technique utilizes the element-specific fluorescence X-rays that are induced by primary ionizing radiation. The fluorescence X-rays from an element of interest are then preferentially imaged onto a detector using an optical train. The preferential imaging of the optical train is achieved using a chromatic lens in a suitably configured imaging system. A zone plate is an example of such a chromatic lens; its focal length is inversely proportional to the X-ray wavelength. Enhancement of preferential imaging of a given element in the test sample can be obtained if the zone plate lens itself is made of a compound containing substantially the same element. For example, when imaging copper using the Cu La spectral line, a copper zone plate lens is used. This enhances the preferential imaging of the zone plate lens because its diffraction efficiency (percent of incident energy diffracted into the focus) changes rapidly near an absorption line and can be made to peak at the X-ray fluorescence line of the element from which it is fabricated. In another embodiment, a spectral filter, such as a multilayer optic or crystal, is used in the optical train to achieve preferential imaging in a fluorescence microscope employing either a chromatic or an achromatic lens.
97 citations