Showing papers on "Diffraction efficiency published in 1980"
TL;DR: In this paper, the theory of Bragg diffraction of finite beams by thick planar gratings is developed, using coupled-wave theory, and analytical expressions for the profiles of the transmitted and diffracted beams in the near field are obtained.
Abstract: The theory of Bragg diffraction of finite beams by thick planar gratings is developed, using coupled-wave theory. Simple analytical expressions for the profiles of the transmitted and diffracted beams in the near field are obtained. Detailed diffraction characteristics for the important case of Gaussian-profile beams are presented. It is shown that the diffraction characteristics depend only on two normalized parameters, the grating strength, and a geometry parameter. The diffraction efficiency and the profiles of the transmitted and diffracted beams are calculated as functions of these two controlling parameters.
69 citations
TL;DR: In this article, the authors present a theoretical and numerical method for solving problems of inverse scattering in optics given data on the far field, find the scattering object and derive the shape of the grating surface.
Abstract: We present a theoretical and numerical method for solving problems of inverse scattering in optics given data on the far field, find the scattering object. This method is applied to perfectly conducting diffraction gratings. From the efficiency curve in a Littrow mounting and in the TE case, we derive the shape of the grating surface. Two different cases must be distinguished. The first problem, which we call “reconstruction,” is to compute the profile when the efficiency is experimentally known. In the second one, called “synthesis,” we give a priori an efficiency curve and look for the corresponding grating(s), if it actually exists. We show several theoretical reconstructions for various gratings, and present our first results in the very difficult field of synthesis. The relevance of this method in the domain of electromagnetic optics is then outlined by its application to two other problems.
54 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: Fresnel lenses in optical waveguides have been designed, analyzed, and experimentally fabricated and evaluated in BaO Waveguides as mentioned in this paper, where diffraction limited spot size, 18 dB of the signalto-noise ratio, angular field of view of 15°, and 23 percent diffraction efficiency have been observed experimentally.
Abstract: Fresnel lenses in optical waveguides have been designed, analyzed, and experimentally fabricated and evaluated in BaO waveguides. Diffraction limited spot size, 18 dB of the signal-to-noise ratio, angular field of view of 15°, and 23 percent diffraction efficiency have been observed experimentally. Limitations of and methods for improving its performanee are discussed.
38 citations
TL;DR: An electron-beam writing apparatus with a computer-processed scanning system has been developed to fabricate various types of microgratings in integrated optical circuits for high-efficiency guided-beam deflection in As(2)S(3) film waveguides.
Abstract: An electron-beam writing apparatus with a computer-processed scanning system has been developed to fabricate various types of microgratings in integrated optical circuits. As one of the most fundamental components, we have fabricated microgratings for high-efficiency guided-beam deflection in As2S3 film waveguides. The design procedure was established for both uniform-period gratings and linearly chirped gratings. Uniform-period gratings 0.2 × 1 mm2 exhibited excellent optical performance as designed, a diffraction efficiency η ≃ 100%. Chirped gratings exhibited wideband selectivity with high diffraction efficiency. Design and experimental results of microdeflection gratings are discussed in detail.
34 citations
TL;DR: In this paper, the theory of diffraction by gratings formed by the interference of two crossed three-dimensional "arbitrary profile plane waves" in a photosensitive medium is developed.
Abstract: The theory of diffraction by gratings formed by the interference of two crossed three-dimensional “arbitrary-profile plane waves” in a photosensitive medium is developed. The detailed diffraction characteristics for the case of crossed-beam gratings formed by two three-dimensional “Gaussian plane waves” are presented. The diffraction efficiencies of these gratings and the profiles of the transmitted and diffracted beams are calculated as functions of the grating strength. The influence of the relative size (the Gaussian beam diameter) of the two writing beams on the diffraction efficiency is determined. Diffraction characteristics for readout with beams of profiles different from those used for writing are presented.
31 citations
TL;DR: Measurements and calculations have been made to investigate the effects due to the change in groove orientation on efficiencies of gratings ruled on a spherical surface and calculations based on electromagnetic theory show good agreement with the experimental data over the 150-2500-A wavelength range.
Abstract: Measurements and calculations have been made to investigate the effects due to the change in groove orientation on efficiencies of gratings ruled on a spherical surface. Typical efficiency maps across the surface are given for various angles of incidence and wavelengths in the VUV and UV regions. Computations based on electromagnetic theory show a good agreement with the experimental data over the 150-2500-A wavelength range. A simple explanation is given to interpret and predict the shape of efficiency maps obtained from both theory and experiments.
25 citations
TL;DR: In this article, a method for calculating the diffracting efficiency of the convex curved crystal spectrograph is presented, and experimental data and calculated values are given for elastically curved potassium acid phthalate (KAP) and plastically curved LiF.
Abstract: A method for calculating the diffracting efficiency of the convex curved‐crystal spectrograph is presented. Experimental data and calculated values are given for elastically curved potassium acid phthalate (KAP) and plastically curved LiF. The calculation method accounts for extinction and anomalous scattering effects. The principal area of application is expected to be diagnostics of the x radiation emitted by hot plasmas.
20 citations
TL;DR: In this article, the angular selectivity of volume diffraction gratings is exploited to form a spatial-frequency filter, which is recorded in a thick recording medium as a superposition of several simple gratings or as a single grating with a modulation that varies in depth.
Abstract: The angular selectivity of volume diffraction gratings is exploited to form a spatial-frequency filter. The filter is recorded in a thick recording medium as a superposition of several simple gratings or as a single grating with a modulation that varies in depth. Such a device can have controlled angular selectivity so as to alter the relative amplitude and phase of selected spatial-frequency components. A coupled-wave formalism is used to analyze the angular selectivity of this device and experimental results demonstrate its usefulness in improving motion-blurred images.
15 citations
TL;DR: This paper has characterized and measured scatter from high efficiency and reflective diffraction gratings and found that the characteristic scatter depends strongly on the way the gratings are fabricated.
Abstract: This paper has characterized and measured scatter from high efficiency and reflective diffraction gratings. Three major types of scatter are identified: (1) random, which occurs over 2π sr; (2) band or ghost scatter, which occurs in the plane of incidence; and (3) structured scatter, which is a symmetrical pattern repeated about each order. Measurements were taken at 10.6 μm on gratings made by ruling, ion etching, holography, or a combination of these techniques. We found that the characteristic scatter from these high efficiency gratings depends strongly on the way the gratings are fabricated.
14 citations
TL;DR: An integrated grating circuit (IGC) for guided-beam multiple division was fabricated in an As2S3 film waveguide by the electron-beam direct-writing technique, and excellent optical performance was demonstrated.
Abstract: An integrated grating circuit (IGC) for guided-beam multiple division was fabricated in an As2S3 film waveguide by the electron-beam direct-writing technique, and excellent optical performance was demonstrated. The circuit was composed of one chirped and three uniform-period gratings, each precisely arrayed to satisfy the Bragg condition. An incident IR guided beam (λ = 1.153 μm) was successfully divided into multiple beams by an IGC of 1.0 × 3.0 mm. Design, fabrication technique, and optical performance of the IGC for guided-beam multiple division are discussed.
TL;DR: In this article, the problem of radiation damage to optical components will become more acute as more powerful synchrotrons come into operation and an understanding of the radiation damage processes should provide guidance to the selection of the most resistant glasses.
TL;DR: Diffraction gratings having well-shaped rectangular profiles were fabricated by chemical etching of single-crystal silicon oriented in the ?
Abstract: Diffraction gratings having well-shaped rectangular profiles were fabricated by chemical etching of single-crystal silicon oriented in the 〈110〉 direction. The grooves were 2.62 μm deep, 5.4 μm wide, and were separated by 10.2 μm. The diffraction behavior was measured near normal incidence using several laser wavelengths. The specularly reflected (zero-order) beam varied by a factor of at least 140 at different visible wavelengths, thereby demonstrating the excellent geometric form of the structures.
TL;DR: The coupled-mode equations are solved for the case of a TEO guided wave obliquely incident upon a waveguide diffraction grating with angular dependence of the TE0-TE0 reflectivity of the grating exhibits a null for an angle of incidence that satisfies a relation that is reminiscent of Brewster's law.
Abstract: The coupled-mode equations are solved for the case of a TE0 guided wave obliquely incident upon a waveguide diffraction grating. The solution involves an approximation in which the coupling coefficient is replaced by its spatial average over one period of the grating. The angular dependence of the TE0−TE0 reflectivity of the grating exhibits a null for an angle of incidence that satisfies a relation that is reminiscent of Brewster's law.
TL;DR: In this article, the authors combine the scan flexibility of computer-generated holographic laser beam scanners with the high diffraction efficiency of volume phase holograms to produce a new type of "holo-scanner" which consists of numerous, small, volume hologram facets recorded in dichromated gelatin films.
Abstract: We combine the scan flexibility of computer-generated holographic laser beam scanners with the high diffraction efficiency of volume phase holograms to produce a new type of "holo-scanner." The scanner-hologram consists of numerous, small, volume hologram facets recorded in dichromated gelatin films and produces an arbitrary output pattern with greater than 90% light efficiency. Experimental results for discrete point, continuous line, and 3-D scanners are shown. Multiwavelength and materials processing scanners are also considered.
TL;DR: In this article, a mode theory for image reconstruction by volume holograms allowing for nonlinearity of the photographic process is developed, and an analysis is made of cases of two possible types of reference wave: coded (i.e., with small-scale inhomogeneities) and plane.
Abstract: A mode theory is developed for image reconstruction by volume holograms allowing for nonlinearity of the photographic process. An analysis is made of cases of two possible types of reference wave: coded (i.e., with small-scale inhomogeneities) and plane. Expressions obtained for the diffraction efficiency can be used to study the spectral and angular selectivity, influence of shrinkage, polarization and other properties of volume holograms allowing for nonlinearity of the photographic process. Optimal intensities of the reference and object waves which can give the maximum diffraction efficiency are determined. The properties of superposed hologram recordings are investigated.
TL;DR: In this paper, a technique has been developed to measure the efficiency of diffraction gratings in the vacuum ultraviolet spectral region at any angle of incidence, and the results show that concave gratings do not have a uniform efficiency over their surfaces.
TL;DR: An antireflection layer of Fe2O3 beneath the photoresist used to record a holographic diffraction grating on a planar waveguide has been shown to result in improved grating depth, and therefore in greater diffraction efficiency, by reducing the effects of standing waves in the film during exposure.
Abstract: An antireflection layer of Fe2O3 beneath the photoresist used to record a holographic diffraction grating on a planar waveguide has been shown to result in improved grating depth, and therefore in greater diffraction efficiency, by reducing the effects of standing waves in the film during exposure.
TL;DR: The design and performance characteristics of a computer interfaced optical memory system that utilizes holographic storage in photorefractive LiNbO(3) crystals are examined and an observed resolution limit agrees closely with a 155-microm limit estimate based on spatial filtering and diffraction considerations.
Abstract: The design and performance characteristics of a computer interfaced optical memory system that utilizes holographic storage in photorefractive LiNbO3 crystals are examined. An observed resolution limit of 145 μm (at 31 cm beyond the hologram) agrees closely with a 155-μm limit estimate based on spatial filtering and diffraction considerations. Angular and wavelength indexing are compared. A 3-D storage density limit of 1010 bits/cm3 is estimated for angular indexing with the viewing angle optimized.
TL;DR: In this paper, Bragg diffraction of light waves in a planar optical waveguide by diffraction gratings of finite aperture and length used as waveguide couplers in integrated optics is analyzed.
Abstract: An analysis is made of Bragg diffraction of light waves in a planar optical waveguide by diffraction gratings of finite aperture and length used as waveguide couplers in integrated optics. In the asymptotic coupled-wave approximation, the complex amplitude of an inhomogeneous diffracted wave is described by a hyperbolic partial differential equation with boundary conditions determined by the profile of the grating and the incident optical beam. The interaction constant of the coupled waves is calculated and its dependence on the diffraction angle is determined for the electric and magnetic modes of a planar optical waveguide. Examples are given of calculations of the diffraction field in the near-field zone for gratings having the configurations of a characteristic parallelogram and trapezium.
Patent•
19 Jun 1980
TL;DR: In this paper, the authors proposed to improve the realiability of the apparatus by changing the exposure to scanning holograms and condensing the reflected light from the target are formed thereon.
Abstract: PURPOSE:To achieve the improvement in the performances of holograms, reduce read errors, etc. and improve the realiability of the apparatus by changing the exposure to scanning holograms and condensing holograms. CONSTITUTION:Photosensitive material is coated on a substrate 4 for holograms and a hologram region 5 for scanning the target by laser light and hologram regions 6 for condensing the reflected light from the target are formed thereon. In this case, the region 5 is exposed under the conditions where the exposure is in the range (a) by using a mask having a light transmission window 7 and a light-blocking part 8, thence the regions 6 are exposed under the conditions where the exposure is in the range (b) by using a mask having light transmission windows 9 and a light blocking part 10. As a result of this, the region 5 becomes high in diffraction efficiency and is improved of S/N and the regions 6 become high in diffraction efficiency and have less differences depending upon places, thus the performances of the holograms improve.
TL;DR: The thick phase-diffraction grating (an elementary hologram) is considered which is obtained as a result of the interference of a plane or inhomogeneous object wave with an evanescent wave in the photographic emulsion resulting from the total reflection of a Gaussian reference beam at the emulsion surface.
Abstract: The thick phase-diffraction grating (an elementary hologram) is considered which
is obtained as a result of the interference of a plane or inhomogeneous object
wave with an evanescent wave in the photographic emulsion resulting from the
total reflection of a Gaussian reference beam at the emulsion surface. The
linear theory of diffraction efficiencies in weak diffraction approximation for
normally polarized light is formulated. Using a digital computer the geometry of
the recording process is optimized, and the uncertainty factor of the
conventional Bragg condition for volume diffraction gratings in the case of
inhomogeneous waves is discussed.
TL;DR: Reflectivity changes and the efficiency of a temporary grating formed on a Ge surface by two beams are compared with those measured for beams of equal frequency and indicate that the observations can be explained by a deterioration in the quality of the grating due to its motion across the surface.
Abstract: Reflectivity changes and the efficiency of a temporary grating formed on a Ge surface by two beams, which differ in frequency by 26 MHz, are compared with those measured for beams of equal frequency. The results indicate that the observations can be explained by a deterioration in the quality of the grating due to its motion across the surface. The predicted effects due to a phase difference between the intensity pattern and the temperature variation on the surface which it produces were not observed.
TL;DR: In this paper, the coherence of the radiation emitted by a compact cw semiconductor laser with a holographic selector, operating at room temperature, was investigated and it was shown that the contrast in the reconstructed image was at least 10:1 and the data storage density was 104 mm2.
Abstract: An investigation was made of the coherence of the radiation emitted by a compact cw semiconductor laser with a holographic selector, operating at room temperature. The coherence length was 20 mm for an output power of 10 mW. Holograms with a diffraction efficiency of 5.5% were recorded. The contrast in the reconstructed image was at least 10:1 and the data storage density was 104 mm2.
Patent•
23 Jul 1980
TL;DR: In this article, the authors proposed to compensate the decrease in diffraction efficiency at the multiple frequency driving by subjecting the ultrasonic light modulator to MFD according to the combination of the control signals which perform intermission of individual diffracted beams.
Abstract: PURPOSE:To compensate the decrease in the diffraction efficiency at the multiple frequency driving by subjecting the ultrasonic light modulator to multiple frequency driving according to the combination of the control signals which perform intermission of individual diffracted beams. CONSTITUTION:High frequency switches 3, 4 are controlled by the control inputs from terminals 11, 12 and ultrasonic waves of different frequencies are mixed through a high frequency mixer 5, by which an ultrasonic light modulator 100 is subjected to multiple frequency driving, then the diffracted laser light fluxes of different angles of deflections are generated. The output of an AND circuit 8 changes to high and low levels according to the states of the control inputs which change with the high and low levels of the terminals 11, 12 which perform the intermission of these respective diffracted beams, by which the amplification factor of an amplification factor variable aplifier 6 is controlled, thus the decrease in the diffraction efficiency of the modulator 100 owing to the interference at the similtaneous application of the multiple frequency driving signals is compensated.
TL;DR: In this paper, a scheme for recording information in a holographic memory is analyzed theoretically and implemented experimentally, which involves the use of a random scatterer imaged in the hologram plane.
Abstract: A scheme for recording information in a holographic memory is analyzed theoretically and implemented experimentally. It involves the use of a random scatterer imaged in the hologram plane. A high noise immunity of the scheme and a high diffraction efficiency of periodic transparencies are reported.
TL;DR: In this paper, a 10.6 μm CO2 laser acoustooptic modulator was fabricated and its performance was investigated using LiNbO3 and Ge materials.
Abstract: By use of LiNbO3 and Ge, a 10.6 μm CO2 laser acoustooptic modulator device is fabricated and its acousto- and optical-modulation characteristics are investigated. When epoxy-type conductive adhesive is applied to LiNbO3 and Ge and the device is annealed thermally at 100° C for more than 20 hours, and the acoustooptic modulator device gives the diffraction efficiency predicted in theory according to the device material and shape. The device yields 8% diffraction efficiency at a driving power of 1W, and 0.11 μs rise time for the case of 1 mm laser beam diameter; when operated below 2W driving power it yields stable operation for a long time.
14 May 1980
TL;DR: In this paper, a statistical analysis of the diffraction efficiency of computer generated holograms for extended objects with a uniform phase distribution was performed and it was shown that a realistic value of 28% was achieved for a simple point object.
Abstract: Reflective holographic optical elements offer a number of advantages over conventional optical elements at the 10.6 μm wavelength of the CO2 laser. One proposed application is to irradiate the appropriate infrared hologram with a high power CO2 laser and use the projected real image for laser materials processing. The required holograms can be ob-tained using computer generation, direct recording at 10.6 μm, or by recording holograms in the visible and converting them to phase reflection holograms. An analysis of the aberrations introduced when holograms are recorded in the visible and the image reconstructed at 10.6 μm shows that aberrations can be made acceptably small even for extended images. A statistical analysis of the diffraction efficiency of computer generated holograms for extended objects with a uniform phase distribution shows that a realistic value for diffraction efficiency is about 28% as compared to about 40% for a simple point object. Phase reflection holograms fabricated using a copper electroplating method have good surface quality and a diffraction efficiency of about 30%.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.