Showing papers on "Diffraction efficiency published in 1989"
14 Aug 1989
TL;DR: In this paper, the theory, design and fabrication of multi-level diffractive profiles are described in detail, and basic examples illustrate the potential usefulness, as well as the limitations of these elements.
Abstract: : Multi-level diffractive phase have the potential to significantly improved the performance of many conventional lens systems. The theory, design and fabrication of these diffractive profiles are described in detail. Basic examples illustrate the potential usefulness, as well as the limitations, of these elements. Keywords: Binary optics; Diffractive optical elements.
309 citations
TL;DR: It is shown that paraxial designs are not adequate for f/Nos.
Abstract: The optical properties of holographic kinoforms are described. It is shown that paraxial designs are not adequate for f /Nos. less than ~F/10. A nonparaxial design is introduced that retains the high diffraction efficiency of the paraxial designs, yet also produces an unaberrated diffracted wavefront for the design wavelength. Aberration calculations and computer calculations, based on the Huygens-Fresnel principle, of the point spread functions for these elements show the necessity of using the nonparaxial design. Specifications for a surface profile that takes account of the finite thickness of the diffracting surface are given. A model for kinoforms which can be used in optical design programs is proposed.
176 citations
TL;DR: The third-order aberrations of a diffractive optical element with paraxial zone spacings are derived as a function of aperture stop position and the distortion of the resulting system is shown to be the proper amount for use as a Fourier transform lens.
Abstract: The third-order aberrations of a diffractive optical element with paraxial zone spacings are derived as a function of aperture stop position. It is shown that by placing the stop in the front focal plane, coma and astigmatism are identically zero, assuming an infinitely distant object. In addition, since the element is diffractive, the Petzval sum is also zero. Modulation transfer function comparisons with other lenses are given. The correction of spherical aberration using an aspheric plate located in the aperture stop and nonmonochromatic imaging performance are discussed. The distortion of the resulting system is shown to be the proper amount for use as a Fourier transform lens. An estimate for the space-bandwidth product of this Fourier transform system is given.
82 citations
TL;DR: In this article, a volume phase hologram was recorded in DMP-128 and the microstructure responsible for the holographic activity was revealed, where solid and porous layers alternate with a spacing commensurate with the recorded fringe pattern.
Abstract: Electron micrographs of volume phase holograms recorded in DMP-128 reveal microstructure that is responsible for holographic activity. Solid and porous layers alternate with a spacing commensurate with the recorded fringe pattern. The difference in material density between the solid and porous regions accounts for the refractive index modulation and therefore the holographic activity of DMP-128 holograms. The pores of the holograms are interconnected and can be filled with many low and moderate viscosity liquids. Diffraction efficiency, bandwidth, and wavelength of maximum efficiency are profoundly and predictably affected by filling the hologram pores.
77 citations
TL;DR: Experimental results that demonstrate the formation of photorefractive gratings in KTN:Cu,V in theparaelectric phase are presented using the quadratic electro-optic effect, which allows amplitude modulation of the diffracted beam by an external electric field.
Abstract: Experimental results that demonstrate the formation of photorefractive gratings in KTN:Cu,V in the paraelectric phase are presented. These gratings are formed using the quadratic electro-optic effect, which allows amplitude modulation of the diffracted beam by an external electric field. High diffraction efficiencies of over 50% in a 3-mm thick sample and amplitude modulation of the diffracted beam by an external field at frequencies of up to 20 kHz were observed.
74 citations
TL;DR: In this paper, transient gratings in room-temperature GaAs/AlGaAs multiple-quantum-well structures made using a sub-picosecond laser system were investigated.
Abstract: We report time-resolved studies of transient gratings in room-temperature GaAs/AlGaAs multiple-quantum-well structures made using a subpicosecond laser system. Forward-traveling and counterpropagating four-wave mixing geometries produced carrier modulation either parallel or perpendicular to the quantum wells such that the highly anisotropic carrier diffusion could be monitored. Carrier heating and cross-well transport was monitored and geometrical control of the diffusion and resulting four-wave mixing time constant demonstrated. Measured diffraction efficiencies gave the refractive-index change of the order of Δn ~ 0.02 at the onset of saturation of the heavy-hole exciton nonlinearity. Implications for refractive optical bistability are discussed through a determination of the limiting conditions for switching.
53 citations
TL;DR: In this paper, the optical nonlinearity of the 3-butylthiophene poly(3butyliophene) was investigated by degenerate forward four-wave mixing at 1.064 μm.
53 citations
TL;DR: Experimental results are reported that demonstrate for the first time, to the knowledge, more than 20 holograms stored and recalled with equal diffraction efficiency in photorefractive LiNbO(3) with an order-of-magnitude increase in Diffraction efficiency with the order of exposure for optically erasable holograms.
Abstract: We report experimental results that demonstrate for the first time, to our knowledge, more than 20 holograms stored and recalled with equal diffraction efficiency in photorefractive LiNbO3. A physical explanation for this new recording procedure is presented, and a comparison is made with previous exposure methods that shows an order-of-magnitude increase in diffraction efficiency with the order of exposure for optically erasable holograms. The procedure holds for recording times much less than the saturation exposure time.
49 citations
TL;DR: In this article, photorefractive gratings are written, read out, and erased with single 30-psec pulses at fluences of 1-15 mJ/cm2 and a wavelength of 0.532 μm in a BaTiO3 crystal.
Abstract: Photorefractive gratings are written, read out, and erased with single 30-psec pulses at fluences of 1–15 mJ/cm2 and a wavelength of 0.532 μm in a BaTiO3 crystal. The gratings consist of one component that is fully formed 50 psec after the peak in the writing beams and a second component that grows for approximately 30 sec until it starts to decay by dark erasure. The photorefractive index change per absorbed photon for picosecond pulses is approximately the same as that obtained when a cw beam at 0.515 μm is used with the same crystal. The index change is approximately a factor of 30 smaller than that observed at the same fluence in GaAs at 1.06 μm when the same picosecond laser system is used.
48 citations
TL;DR: A recursive design technique for forming holographic elements which can be incorporated into helmet displays has been developed and it is illustrated for a single holographic helmet display element having resolution less than 0.8 mrad and diffraction efficiency more than 80 percent over a field of view of 16 degrees x 16 degrees.
Abstract: A recursive design technique for forming holographic elements which can be incorporated into helmet displays has been developed To ensure that the holographic elements have low aberrations and high diffraction efficiency they must be recorded with complex wavefronts These wavefronts are derived from relatively simple intermediate holograms whose readout geometry and wavelength differ from those during recording The overall recursive design technique is illustrated for a single holographic helmet display element having resolution of less than 08 mrad and diffraction efficiency of more than 80 percent over a field of view of 16 degrees x 16 degrees
47 citations
TL;DR: The diffraction by two planar slanted fringe gratings superposed in the same volume of an anisotropic medium is treated using rigorous 3-D vector coupled wave analysis using the various Bragg conditions identified and quantified.
Abstract: The diffraction by two planar slanted fringe gratings superposed in the same volume of an anisotropic medium is treated using rigorous 3-D vector coupled wave analysis. Arbitrary angle of incidence and polarization are included. Both phase and/or amplitude slanted gratings in anisotropic media are treated in the analysis. The external boundary regions can be either isotropic (for bulk applications) or uniaxial anisotropic (for integrated applications). Both forward- and backward-diffracted orders are characterized by a number pair (i1,i2), where i1 and i2 are integers. The Floquet condition is discussed for the case of two superposed gratings. When the external regions are anisotropic, each diffracted order has an ordinary (O), and an extraordinary (E) component. The analysis is also generalized for an arbitrary number of superposed gratings. The numerical complexity is discussed. In the case of equal grating periodicities along the boundaries, the diffracted orders become degenerate in the external regions. In this case, an alternative analysis that utilizes a cascaded stack of unslanted gratings can be used. Limiting cases are also presented. The various Bragg conditions are identified and quantified. Sample calculations presented include the quantification of the crosstalk between two superposed gratings, the evaluation of the effects of coupled Bragg conditions in beam combining applications, design and analysis of a beam splitter and a beam combiner, demonstration of the use of a cascaded stack of unslanted gratings of constant modulation to represent two superposed gratings that have the same periodicity along the boundaries, and finally evaluation of the effect of the phase difference between two gratings. The same analysis applies in the limiting cases of isotropic materials, single slanted gratings, etc. Applications of this analysis include optical storage, optical digital truth table look-up processing, neural nets, optical interconnects, beam splitting, and beam combining.
TL;DR: Experimental results are reported for four-wave mixing at 633 nm with a photorefractive Bi(12)TiO(20) crystal in a double phase-conjugate mirror geometry that yields up to 40% diffraction efficiency for the hologram.
Abstract: Experimental results are reported for four-wave mixing at 633 nm with a photorefractive Bi12TiO20 crystal in a double phase-conjugate mirror geometry. Recording in the presence of an alternating electric field with optimum focusing of interacting Gaussian beams yields up to 40% diffraction efficiency for the hologram.
Patent•
02 Aug 1989
TL;DR: In this article, the authors characterized an optical head device for reading information stored in a recording medium, where a light beam from a light source is converged on an optical disk and a reflected beam from the optical disk is received by a light receiving element.
Abstract: An optical head device for reading information stored in a recording medium (16) wherein a light beam from a light source is converged on an optical disk and a reflected beam from the optical disk is received by a light receiving element (17) thereby to read out information stored in the optical disk is characterized in comprising a diffraction element (13) including: first diffraction gratings (13e, f) for dividing the light beam from the light source into a 0th order diffracted beam utilized for reading out the information stored in the optical disk and a pair of first order diffracted beams utilized for reading tracking errors; and second diffraction gratings (13a-d) for guiding the reflected beam from the optical disk to the light receiving element. The transmission factors of 0th order diffracted beam of the first and/or second diffraction gratings in the regions located in the vicinity of both ends of the diffraction element are lower than those of the first and/or second diffraction gratings in the regions located in the vicinity of the center of the diffraction element, the ends and center being set in a corresponding direction to the radial direction of the optical disk.
TL;DR: In this paper, the Dammann grating concept was generalized to generate 2D patterns of discrete light spots with low reconstruction error and high diffraction efficiency, typically ≈ 30% in arbitrary (off-axis), and ≈ 60% in inversion symmetric (on-axis) patterns.
TL;DR: In this paper, a beam splitter which can split one beam of a laser into an array of 25x25 uniform intense beams has been designed and fabricated, which shows uniformity better than 96% and diffraction efficiency over 60%.
TL;DR: In this paper, it is shown that, with four mirrors around a lossless hologram of low diffraction efficiency, it is possible to choose mirror reflectivities to provide 100% diffraction efficiencies.
Abstract: We consider several aspects of holographic optical interconnects. First we outline the various categories of holographic interconnects. We then show that obtaining a large number of superimposed holographic interconnects, all of high efficiency, in one hologram is difficult with present materials. Resonant mirrors around the hologram are suggested as a solution. It is shown that, with four mirrors around a lossless hologram of low diffraction efficiency, it is possible to choose mirror reflectivities to provide 100% diffraction efficiency. Angular beam widths and a recommended configuration are also presented.
CNET1
TL;DR: In this paper, the effect of absorption on double phase conjugate mirror (DPCM) in photorefractive materials is studied and an analytical condition for the threshold is derived; in particular the 2WM gain Γ and the absorption α must satisfy γ>2α.
TL;DR: In this work a moving point source is adopted and analysis indicates that if the path is a circle several of these restrictions are removed, resulting in high-efficiency gratings being produced at frequencies up to 2400 lines/mm.
Abstract: In the manufacture of holographic gratings using coherent light there is an associated problem of optical noise, the conventional remedies for which involve various restrictions. In this work a moving point source is adopted and analysis indicates that if the path is a circle several of these restrictions are removed. The scheme is implemented and the results are highly satisfactory with high-efficiency gratings being produced at frequencies up to 2400 lines/mm, in sizes up to 65 mm square. Significant operational advantages also accrue in relation to alignment procedures and light utilization.
TL;DR: In this article, the authors reported the measurement of diffusion transport length LD, quantum efficiency φ for photoelectron generation, and the Debye screening length and associated trap density NA in an undoped Bi12SiO20 (BSO) photorefractive crystal.
Abstract: We report the measurement of diffusion transport length LD, quantum efficiency φ for photoelectron generation, and the Debye screening length and associated trap density NA in an undoped Bi12SiO20 (BSO) photorefractive crystal. The method is based on the optical erasing of holographically recorded gratings in the crystal. The measurement of the diffraction efficiency evolution is considerably facilitated profitting from polarization properties of anisotropic diffraction in BSO‐type crystals in a self‐diffraction experiment. Data processing is carried out using simple linear regression techniques for experimental conditions in two limiting situations: far from and well into trap saturation conditions. We prove that optical erasure closely verifies the decay law predicted by theory even if a highly contrasted pattern of light is used for recording. We measured NA=6.3×1016 cm−3, agreeing in order of magnitude, with already reported values, but found out LD=0.1 μm, which is too much lower than data in literat...
TL;DR: The results of an experimental investigation on the storage life and reprocessibility of methylene blue sensitized dichromated gelatin (MBDCG) holograms indicate that the diffraction efficiency can be stabilized through storage in a relatively short period of time.
Abstract: The results of an experimental investigation on the storage life and reprocessibility of methylene blue sensitized dichromated gelatin (MBDCG) holograms are reported. The major conclusions of the investigation are: (i) Storage of MBDCG holograms in normal laboratory conditions for long periods is possible and it diminishes somewhat their diffraction efficiency. (ii) The results on short time storage and long time storage are almost similar, thus indicating that the diffraction efficiency can be stabilized through storage in a relatively short period of time. (iii) The deterioration in the diffraction efficiency on storage is less [D(eta) 80%] for gratings of low/medium initial efficiency (eta <75%) whereas it is rather imperfect for gratings having high initial efficiency.
TL;DR: It is found that for high beam ratios the diffraction efficiency quickly reaches a relatively low limit and remains nearly constant as the exposure is increased, and a model is presented which explains this saturation by a simple relationship between the refractive index modulation and the exposure maxima and minima.
Abstract: Experimental results are presented of the diffraction efficiencies of holograms recorded in bleached silver-halide emulsions for varying beam ratio and exposure. It is found that for high beam ratios the diffraction efficiency quickly reaches a relatively low limit and remains nearly constant as the exposure is increased. A model is presented which explains this saturation by a simple relationship between the refractive index modulation and the exposure maxima and minima. The effect of noise gratings on the depletion of the transmitted and diffracted beams is also investigated by measurements at different replay directions and at two different wavelengths.
TL;DR: Tungsten/beryllium multilayers were coated onto lamellar diffraction gratings using a neutral atom beam sputtering technique as discussed by the authors, and the boundary roughness of the multilayer was estimated to be 6.0 A as a standard deviation.
Abstract: Tungsten/beryllium multilayers were coated onto lamellar diffraction gratings using a neutral atom beam sputtering technique. Boundary roughness of the multilayer was estimated to be 6.0 A as a standard deviation. Diffraction efficiency of the multilayer‐coated grating was measured using monochromatized synchrotron radiation.
IBM1
TL;DR: An elementary theory is presented that relates the characteristics of the second-harmonic diffraction pattern to the spatially varying properties of the surface and is applied to infer the adsorbate density profile of the spatually modulated grating.
Abstract: Diffracted surface second-harmonic radiation emerging in several orders has been observed from a periodically modulated monolayer of adsorbed dye molecules. The molecular grating was produced by laser-induced desorption in the field of two crossed beams. An elementary theory is presented that relates the characteristics of the second-harmonic diffraction pattern to the spatially varying properties of the surface and is applied to infer the adsorbate density profile of the spatially modulated grating. The density profile is compared with the predictions of a model of grating formation based on thermal desorption.
TL;DR: In this paper, the remarkable acousto-optical properties of superlattices for light wavelength near the condition of the Bragg reflection at the interfaces are reported for the first time.
Abstract: The remarkable acousto‐optical properties of superlattices for light wavelength near the condition of the Bragg reflection at the interfaces are reported here for the first time. Because of the assistance of a reciprocal lattice vector in the phase‐matching condition, the collinear coupling between the light and ultrasonic waves becomes possible in the superlattice. At the same time, the diffraction efficiency is strongly increased by an optical resonance effect in the superlattice. Acousto‐optical devices based on semiconductor superlattice structures are proposed, which can be very efficient, rapid, and compact.
TL;DR: The holographic double-exposure technique is applied to elementary gratings in photorefractive crystals and the result is an interconnection strength that is a continuous function of the phase shift between the two gratings.
Abstract: The holographic double-exposure technique is applied to elementary gratings in photorefractive crystals. The result is an interconnection strength that is a continuous function of the phase shift between the two gratings. In fan-in and fan-out situations, where multiple phase gratings are required, it is possible to alter each interconnection separately without affecting the others.
TL;DR: In this paper, the diffraction of finite bounded beams with arbitrary profiles by nonuniform, arbitrarily bounded mixed volume gratings is described, taking into account deviations from the Bragg condition, attenuation of the modulation depth, and constant absorption.
Abstract: On the basis of two-dimensional coupled-wave theory, the diffraction of finite bounded beams with arbitrary profiles by nonuniform, arbitrarily bounded mixed volume gratings is described, taking into account deviations from the Bragg condition, attenuation of the modulation depth, and constant absorption. The resulting differential equations are solved numerically with a two-dimensional Runge–Kutta method. The quality of the diffracted beam is influenced strongly by the deviation from the Bragg case. Planar finite gratings in contrast to crossed-beam gratings, show a smoothing effect of the diffraction characteristics. This is also found for crossed-beam gratings with a moderate attenuation. It is demonstrated that the amplitude profiles of the grating writing beams and the readout beams have a strong influence on the intensity profiles of the diffracted beams.
TL;DR: In this paper, the authors analyzed diffraction of plane waves by dielectric surface-relief gratings with conic (elliptic, hyperbolic, parabolic) cross-sectional grating shapes using a simple transmittance theory.
Abstract: Diffraction of plane waves by dielectric surface-relief gratings with conic (elliptic, hyperbolic, parabolic) cross-sectional grating shapes is analyzed, using a simple transmittance theory. Integral expressions for the complex amplitudes of the diffracted waves are given for these structures. The calculated results indicate new types of diffraction behavior compared with corresponding results for the commonly studied grating shapes (sinusoidal, rectangular, triangular). In particular, these structures are shown to exhibit a large number of diffracted waves with similar intensities. It is also shown that a bandpasslike behavior (a variable number of fairly even-intensity orders with reasonably sharp cutoff) is obtainable.
TL;DR: Three models for multiplexed transmission gratings are compared and the underlying assumptions for each model are changed to allow an examination of the effects of generating higher diffraction orders and coupling between diffraction Orders on the efficiency and SNR of these gratings.
Abstract: Three models for multiplexed transmission gratings are compared. The underlying assumptions for each model are changed to allow an examination of the effects of generating higher diffraction orders and coupling between diffraction orders on the efficiency and SNR of these gratings. The influence of grating thickness, grating number, and object beam angle is also examined.
TL;DR: In this article, a reconfigurable optical routing switch using photorefractive crystals with non-destructive readout is presented, which reduces the order of complexity from n2 to n for a general two-wavelength n × n holographic interconnection network.
Abstract: A novel architecture for a reconfigurable optical routing switch using photorefractive crystals with nondestructive readout is presented. This design reduces the order of complexity from n2 to n for a general two-wavelength n × n holographic interconnection network. The packing capacity of the network is discussed and is calculated to be of the order of 1000 × 1000 for an ideal volume holographic recording material. In practice, we show that the actual value is constrained by the number of gratings that can be multiplexed in a single photorefractive crystal. A 2 × 3 switch is demonstrated by using a Bi12GeO20 crystal with 514-nm writing beams and 633-nm signal (readout) beams.