Showing papers on "Diffraction efficiency published in 1992"
TL;DR: Coupled-wave analysis is used to design binary gratings with high efficiencies (70-80%) and uses subwavelength structures within each period in order to achieve high efficiency.
Abstract: Coupled-wave analysis is used to design binary gratings with high efficiencies (70-80%). The binary designs have grating periods greater than one wavelength but use subwavelength structures within each period in order to achieve high efficiency.
176 citations
TL;DR: The integrated efficiency is shown to be the limiting value for the optical transfer function; in most cases it serves as an overall scale factor for the transfer function.
Abstract: Diffractive lenses differ from conventional optical elements in that they can produce more than one image because of the presence of more than one diffraction order. These spurious, defocused images serve to lower the contrast of the desired image. We show that a quantity that we define as the integrated efficiency serves as a useful figure of merit to describe diffractive lenses. The integrated efficiency is shown to be the limiting value for the optical transfer function; in most cases it serves as an overall scale factor for the transfer function. We discuss both monochromatic and polychromatic applications of the integrated efficiency and provide examples to demonstrate its utility.
133 citations
TL;DR: In this paper, the design of advanced diffraction gratings that produce spot arrays is highly influenced by the computational capabilities that are available to the designer, which is due to the increased pattern complexity that is required for larger spot arrays or higher efficiencies.
Abstract: The design of advanced diffraction gratings that produce spot arrays is highly influenced by the computational capabilities that are available to the designer. This is due to the increased pattern complexity that is required for larger spot arrays or higher efficiencies. Symmetries that lead to a significant reduction in the design complexity can be incorporated into the grating pattern. In addition, a translational symmetry leads to the highly desired result of even-numbered spot arrays. We examine the symmetries that can be applied to both general-and discrete-level design parameterization.
129 citations
TL;DR: In this paper, the growth and characterization of a new photorefractive material, potassium lithium tantalate niobate (KLTN), was reported and a KLTN crystal doped with copper was demonstrated to yield high diffraction efficiency of photore-fractive gratings in the paraelectric phase.
Abstract: We report the growth and characterization of a new photorefractive material, potassium lithium tantalate niobate (KLTN). A KLTN crystal doped with copper is demonstrated to yield high diffraction efficiency of photorefractive gratings in the paraelectric phase. Voltage-controllable index gratings with n, = 8.5 x 10^-5 were achieved, which yielded diffraction efficiencies of 75% in a 2.9-mm-thick sample. In addition, diffraction was observed in the paraelectric phase without an applied field. This effect is attributed to a growth-induced strain field.
106 citations
TL;DR: In this article, a unified treatment of the diffraction properties of stratified volume holographic optical elements (SVHOE) is presented, where the relative phasing of diffraction orders as they propagate from layer to layer gives rise to a unique notched diffraction response.
Abstract: We present a unified treatment of the diffraction properties of stratified volume holographic optical elements (SVHOE’s). We show that the relative phasing of the diffraction orders as they propagate from layer to layer gives rise to a unique notched diffraction response of the +1 order (for the case of Bragg incidence) as a function of the normalized buffer-layer thickness, the grating spatial frequency, and the readout wavelength. For certain combinations of these parameters Bragg diffraction behavior characteristic of volume holographic optical elements (VHOE’s) is observed, whereas for other combinations pure Raman–Nath behavior periodically recurs. By using these same relative-phasing arguments, the principal features of the periodic angular sensitivity of the +1 and −1 orders can be predicted. In addition to examining the fundamental aspects of SVHOE diffraction behavior, we discuss several possible applications, including optical array generation, spatial frequency filtering, and wavelength notch filtering. With the use of the SVHOE concept, holographic materials with otherwise exemplary characteristics that are currently available only in thin-film form can be used in structures designed either to access unique SVHOE diffraction properties or to emulate conventional VHOE’s.
86 citations
TL;DR: In this article, a coupled-wave description of zone plates with high aspect ratios is given, and the concept of optical thickness is used to consider the change in the diffraction properties of a high resolution micro zone plate with increasing radius.
85 citations
TL;DR: In this article, the fullerene molecule C60 is shown to act as a useful sensitizer of a recently discovered photorefractive polymer, and the sensitization appears to result from a small increase in the carrier generation efficiency and a larger increase in useful optical absorption at the operating wavelength, 647 nm.
Abstract: The fullerene molecule C60 is shown to act as a useful sensitizer of a recently discovered photorefractive polymer. Measurements of the steady‐state diffraction efficiency, grating growth rate, and other photorefractive properties are presented as a function of C60 concentration, writing intensity, and applied electric field. The dc photoconductivity, grating growth rate, and steady‐state diffraction efficiency all increase by as much as a factor of 20 upon doping with up to 0.2 wt % C60. The sensitization appears to result from a small increase in the carrier generation efficiency and a larger increase in the useful optical absorption at the operating wavelength, 647 nm.
81 citations
TL;DR: In this article, the problem of synthesizing, in the framework of the electromagnetic theory, various types of periodic resonance-domain diffractive optical elements that utilize several diffraction orders was considered.
Abstract: Resonance-domain diffractive optics covers the region where the characteristic feature sizes in the surface-relief modulation structure of the diffractive optical element are comparable to the wavelength of light; it may be viewed as a bridge between synthetic holography and the electromagnetic theory of diffraction gratings and rough surfaces. We consider the problem of synthesizing, in the framework of the electromagnetic theory, various types of periodic resonance-domain diffractive optical elements that utilize several diffraction orders. Parametric optimization is used to design one-to-N fan-out elements, N-to-N star couplers, and polarization-controlled optical beam splitters and switches with close to 100% efficiencies and no undesired diffraction orders in the image half-space. Reflection-type fan-out gratings with six and seven output beams are demonstrated experimentally at λ = 10.6 μm.
76 citations
TL;DR: To maximize the efficiency of dielectric diffractive optical elements, the local groove shape is optimized using the rigorous diffraction theory of multilevel surface-relief gratings.
Abstract: To maximize the efficiency of dielectric diffractive optical elements, we optimized the local groove shape using the rigorous diffraction theory of multilevel surface-relief gratings.
67 citations
TL;DR: In this paper, a coupledmode analysis of superimposed holographic transmission gratings in single-mode planar optical waveguides is presented, where the diffraction characteristics are shown to be sensitive to the polarization of the incident wave, the angular separation of the output waves and the relative index modulation between the gratings.
Abstract: A coupled-mode analysis of superimposed holographic transmission gratings in single-mode planar optical waveguides is presented. The diffraction characteristics are shown to be sensitive to the polarization of the incident wave, the angular separation of the output waves and the relative index modulation between the gratings. The coupling between gratings affects the diffraction efficiencies and decreases the angular and wavelength selectivities. Nevertheless, good channel separation and high fanout can be obtained together. >
66 citations
TL;DR: An intraplanar interconnection scheme using substrate guided modes in conjunction with a highly multiplexed waveguide volume hologram is proposed in this article, where a coordinate transformation converts the 3D diffraction problem into a 2D one, which significantly simplifies the theoretical calculation.
Abstract: An intraplanar interconnection scheme using substrate guided modes in conjunction with a highly multiplexed waveguide volume hologram is proposed. Acoustooptically addressed 1-to-50 passive and 1-to-2-to-100 reconfigurable interconnections with a fan-out diffraction efficiency of 55% at 514-nm wavelength are demonstrated. A coordinate transformation converts the 3-D diffraction problem into a 2-D one, which significantly simplifies the theoretical calculation. Intraplane massive fan-out optical interconnection using substrate guided mode provides both collinear and coplanar fan-out capability for data and clock signals. Colinearity of signal distribution allows the 2-D input signal array to be processes. The laminated waveguide device containing a highly multiplexed dichromated gelatin (DCG) hologram has been evaluated. >
TL;DR: Agreement with Kogelnik's two-wave diffraction theory for phase gratings, the time considerations and its effect on dynamic range, the necessity of a pre-illumination pulse, and good image quality at readout are reported.
Abstract: Multiple images were recorded in DuPont HRF-150 photopolymer as transmission holograms by using angle multiplexing. Agreement with Kogelnik's two-wave diffraction theory for phase gratings, the time considerations and its effect on dynamic range, the necessity of a pre-illumination pulse, and good image quality at readout are reported.
TL;DR: The embossing technique that was used for replicating the grating patterns from photoresist onto polycarbonate proved to be a feasible method for the production of such gratings.
Abstract: We employed the rigorous vector coupled-wave theory [J Opt Soc Am 73, 1105 (1983)] to analyze the electromagnetic scattering from two dimensional (2-D) surface-relief dielectric gratings A shoot-back method was developed for the numerical solution of the resulting coupled differential equations This method allowed numerical solutions to be found for grating structures of arbitrary profiles and relatively deep grooves It was most suitable where the grating medium refractive index was not too large and where only a small number of propagating orders existed Experiments confirmed the numerically predicted reflectivities for 2-D surface-relief dielectric sinusoidal gratings Reflectivity measurements were made on 2-D sinusoidal gratings fabricated on photoresist and on polycarbonate The grating periodicities were of the order of 3000 lines/mm such that only the zero-order diffracted waves were propagating in the incident region, and possibly a few forward orders in the transmission region The embossing technique that was used for replicating the grating patterns from photoresist onto polycarbonate proved to be a feasible method for the production of such gratings
TL;DR: The conditions for achieving high-contrast fringes with such an achromatic holographic configuration are analyzed and it is shown that the depth of focus depends only on the spatial coherence of the source.
Abstract: For the fabrication of large-area, spatially coherent gratings with periods of 100 nm or less, a grating interferometer is preferred over a conventional holographic configuration because of the limited coherence of available sources. Using a configuration that employs two matched fused silica phase gratings and an ArF excimer laser, we obtain high-quality 100-nm gratings in polymethyl methacrylate. We analyze the conditions for achieving high-contrast fringes with such an achromatic holographic configuration and show that the depth of focus depends only on the spatial coherence of the source. We also describe a highly accurate method for calculating the diffraction efficiency of the phase gratings as a function of polarization, incidence angle, and grating structure.
TL;DR: Substrate wave propagation and Bragg diffraction by multiplexed holographic gratings have been used to demonstrate a new 1-to-30 fanout optical interconnect having an overall diffraction efficiency of 87.8% and individual channel efficiency of 3.0 +/- 0.8%.
Abstract: Substrate wave propagation and Bragg diffraction by multiplexed holographic gratings have been used to demonstrate a new 1-to-30 fanout optical interconnect having an overall diffraction efficiency of 87.8% at 514.5 nm and an individual channel efficiency of approximately 3.0 +/- 0.8%. The device configuration utilizes the large multiplexing capability of dichromated gelatin polymer films and substrate total internal reflection to realize large channel fanouts within the plane of a soda-lime glass substrate. A simplified theoretical formulation is presented to treat the corresponding three-dimensional holographic diffraction problem in the Bragg regime for slanted phase gratings. Results are compared with experimentally measured quantities for singly exposed phase gratings in different polarization conditions and incident angle orientations. The limitations of using multiplexed holograms in multiplanar substrate interconnection applications are also discussed.
TL;DR: In this article, a technique for forming nondiffracting beams having essentially constant intensity along the propagation direction is presented, where two phase-only holographic elements are exploited to form the nondiffractive beam as well as to obtain a high diffraction efficiency.
01 Apr 1992
TL;DR: In this article, the diffraction efficiency and nonlinear transmission properties of chemically enhanced thin films of bacteriorhodopsin were analyzed by using absorption spectroscopy, the Kramers-Kronig transformation, coupled wave theory, and a simplified kinetic model of the photocycle.
Abstract: The diffraction efficiency and nonlinear transmission properties of chemically enhanced thin films of bacteriorhodopsin are analyzed by using absorption spectroscopy, the Kramers-Kronig transformation, coupled wave theory, and a simplified kinetic model of the bacteriorhodopsin photocycle. Photoconversion of bR to a 50:50 mixture of bR and M generates a large change in refractive index that is proportional to the bacteriorhodopsin concentration and is greatest in regions where the difference in absorption coefficients is smallest. The predicted diffraction efficiencies are dominated by large phase components in regions of minimal bR and M absorption. The maximum diffraction efficiency (11) for a 2.5 OD, 150 micrometers thick film occurs at readout wavelengths between 620 nm - 700 nm. These films also exhibit significant nonlinearity in transmissivity at low laser intensities and could find potential use in spatial filtering applications. A real time optical associative memory based on holographic thin films of bacteriorhodopsin is also discussed.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the authors achieved a diffraction efficiency of 94% and uniformity of better than 8% for a 9 × 9 fan-out element, achieving the best published results for 2D surface-relief fanout elements.
Abstract: Continuous surface-relief phase gratings for two-dimensional (2-D) array generation have been realized by laser-beam writing lithography For a 9 × 9 fan-out element, a diffraction efficiency of 94% and a uniformity of better than ±8% have been achieved These are, to our knowledge, the best published results for 2-D surface-relief fan-out elements Separable and nonseparable solutions for the design of 2-D fan-out elements are discussed
TL;DR: The diffractive multifocal intraocular lens is implanted in the eye to replace a cataractous crystalline lens and Axially separated images from two diffraction orders provide near and distance vision.
Abstract: The diffractive multifocal intraocular lens is implanted in the eye to replace a cataractous crystalline lens. Axially separated images from two diffraction orders provide near and distance vision. Overall image quality is affected by both the quality of the in-focus component and the energy distribution between images. Modulation transfer function and energy distribution data are presented. Measurement accuracy is limited by the diameter of the point spread function and by the difficulty in separating the focused and defocused components.
TL;DR: In this paper, the photorefractive efficiency of Bi2TeO5 was studied as a function of the wavelength, intensity, polarization direction, and crossing angle of the laser write beams, and the sample orientation.
Abstract: Single crystals of Bi2TeO5, both undoped and doped with transition‐metal‐ion dopants, were grown with high optical quality. Continuous‐wave four‐wave‐mixing experiments on these crystals show a strong photorefractive signal with a multicomponent decay. The photorefractive efficiency was studied as a function of the wavelength, intensity, polarization direction, and crossing angle of the laser write beams, and the sample orientation. Both absorption and phase gratings were observed with their relative strengths dependent on the laser wavelength and sample dopants. The signal evolves in time from a defect population grating, to trapped charge gratings involving two different types of traps, to fixed gratings produced by oxygen ion displacements. The photorefractive effect in this material is found to be of the photoconductive type and it produces a larger diffraction efficiency than that observed in sillenite materials under the same experimental conditions. A mechanism is proposed for the various physical processes leading to the different decay components of the signal.
Patent•
23 Oct 1992
TL;DR: An improved method for storing permanent holographic gratings in photorefractive materials for use in narrow band filters such as the H60 filter, as well as the filters themselves was proposed in this paper.
Abstract: An improved method for storing permanent holographic gratings in photorefractive materials for use in narrow band filters such as the H60 filter, as well as the filters themselves. The invention also provides an improved method of controlling the electric field and the nature of the photorefraction to minimize wavelength shifts and band broadening at a minimal reduction of diffraction efficiency.
TL;DR: Single-pulse and cw measurements of the response of a semi-insulating CdZnTe/ ZnTe multiple-quantum-well photorefractive device are presented and it is shown that with an optimized structure the ultimate response time of the device can be below 100 ps.
Abstract: Single-pulse and cw measurements of the response of a semi-insulating CdZnTe/ZnTe multiple-quantum-well photorefractive device are presented. In single-pulse experiments, photodiffractive (absorption) gratings have been written with less than 1.8-microJ/cm(2) incident fluence, and a diffraction efficiency of 1.1% is obtained from the 1.56-microm active layer of the device. With an optimized structure, the ultimate response time of the device can be below 100 ps. In cw measurements a maximum diffraction efficiency of 1.35% is obtained.
TL;DR: In this paper, the performance of photorefractive Sr0.6Ba0.4Nb2O6 under an externally applied voltage was compared with predictions of Kukhtarev's solution.
Abstract: We characterize the performance of photorefractive Sr0.6Ba0.4Nb2O6 under an externally applied voltage. We compared the field dependences of the gain coefficient, response time, sensitivity, and diffraction efficiency with predictions of Kukhtarev’s solution [ Sov. Tech. Phys. Lett.2, 438 ( 1976)] for two-wave interaction, using material parameters obtained at zero voltage. Plane-wave holograms were superimposed in the crystal with angular multiplexing. The hologram capacity (or minimum diffraction efficiency) increased by an order of magnitude with a 15-kV/cm applied field.
TL;DR: An analytical series solution is derived within the Rayleigh hypothesis to compute the efficiencies of a crossed grating illuminated by an arbitrary polarized beam.
Abstract: An analytical series solution is derived within the Rayleigh hypothesis to compute the efficiencies of a crossed grating illuminated by an arbitrary polarized beam. A comparison with previously reported numerical results for a dielectric crossed grating illuminated by a plane wave shows good agreement. The formulas given can be directly implemented on a personal computer.
TL;DR: A range of space-invariant and space-variant holographic optical interconnections are demonstrated with the aid of a nematic liquid-crystal panel that is capable of nearly continuous phase modulation.
Abstract: A range of space-invariant and space-variant holographic optical interconnections are demonstrated with the aid of a nematic liquid-crystal panel that is capable of nearly continuous phase modulation. Results on fan-out, nearest-neighbor/next-nearest-neighbor interconnects, and 8-bit perfect shuffle are presented. The diffraction efficiencies are close to 15% of incident light in all cases.
TL;DR: The design of two broadband hybrid diffractive-refractive optical systems, a landscape lens, and a Schmidt telescope are investigated, which evaluated polychromatic image quality, accounting for diffraction efficiency, by constructing weighted geometric point-spread functions from several diffracted orders.
Abstract: We investigated the design of two broadband hybrid diffractive–refractive optical systems, a landscape lens, and a Schmidt telescope. The systems were achromatized by using the characteristically large negative dispersion of kinoforms. In the scalar wave regime kinoforms can approach 100% efficiency but only for one object point and wavelength. We evaluated polychromatic image quality, accounting for diffraction efficiency, by constructing weighted geometric point-spread functions from several diffracted orders and then calculating modulation transfer functions (MTF’s). The MTF’s of the hybrid achromats were improved at high spatial frequencies but were reduced at low frequencies because of diffraction into nondesign orders.
Patent•
23 Oct 1992TL;DR: In this article, a laser beam passes through two holograms or through a hologram twice to reduce the ratio λ/d, where λ is the wavelength of the laser beam and d is the grating constant of the hologram.
Abstract: A laser beam passes through two holograms or through a hologram twice to reduce the ratio λ/d so that P-polarized light, as well as S-polarized light, can be diffracted with high diffraction efficiency and uses a hologram or holograms formed on a base plate and facilitates the separation of a stamper from the base plate in producing replicas of the hologram. A laser beam (5) passes through two holograms formed on a transparent base plate or through a hologram formed on a transparent base plate twice. The ratio λ/d, where λ is the wavelength of the laser beam and d is the grating constant of the hologram, is in the range of 0.4 to 1.1.
TL;DR: Results of material studies show that phase gratings with high modulation and low absorption can be produced, and a coupled-wave analysis is used to calculate the likely grating performance, and some initial grating characterization results are presented.
Abstract: The extension of holographic techniques from the visible to the infrared is important. Potentially, holographic diffractive elements have a large range of uses in this wave band. Examples include mirrors, lenses, filters, and beam combiners. All these elements would have similar advantages to those enjoyed by their visible band diffractive analogs. The metal photodissolution effect in chalcogenides shows promise as one of the few techniques for producing low-loss holographic materials for use at any given wavelength from 0.6 to beyond 16 microm. To date, the work has concentrated on the photodissolution of silver into arsenic sulfide glasses. Both bulk and surface relief gratings can be fabricated simply by holographic or mask exposure. In principle, kinoforms (e.g., blazed zone plates) and Fresnel lenses can also be made. The results of material studies show that phase gratings with high modulation and low absorption can be produced. A coupled-wave analysis is used to calculate the likely grating performance, and some initial grating characterization results are presented. The limitations of the medium are discussed and possible solutions are considered.
TL;DR: A new photopolarimeter that employs polarization-dependent conical diffraction of light by a metallic grating for the simultaneous measurement of the four Stokes parameters of light is described.
Abstract: A new photopolarimeter that employs polarization-dependent conical diffraction of light by a metallic grating for the simultaneous measurement of the four Stokes parameters of light is described.
TL;DR: The experimental results of the diffraction efficiency study of a hologram in crossed polarizers, referring to azo-dye-colored films, are in good agreement with the theoretical results.
Abstract: The diffraction efficiency of a hologram in crossed polarizers, recorded by means of photoinduction of the optical anisotropy in a film with a different orientation of the polarization planes of interfering plane waves, is studied. The dependence between the diffraction efficiency of the hologram and the angle of orientation against the optical axis of the analyzer is determined both theoretically and experimentally. The theoretical calculations are based on the assumption that the photoinduction of anisotropy is due to the formation of anisotropic grains following exposure to light and only the concentration of grains is a function of exposure. The experimental results, referring to azo-dye-colored films, are in good agreement with the theoretical results of the given work.