Showing papers on "Diffraction efficiency published in 1976"
TL;DR: In this paper, the best known photorefractive sensitivity for read-write volume holographic storage (S−1≃300 μJ/cm2) combined with high quality image reconstruction was identified.
Abstract: Bi12SiO20 and Bi12GeO20 present the best known photorefractive sensitivity for read‐write volume holographic storage (S−1≃300 μJ/cm2) combined with high‐quality image reconstruction. Recording processes by photocarrier diffusion (no applied field) and by photocarrier drift are identified. The high photosensitivity is attributed to photocarrier displacements comparable to or larger than fringe spacings. Saturation diffraction efficiency at light power densities larger than 600 μW/cm2 at λ=514.5 nm occurs from complete photocarrier trap filling.
193 citations
TL;DR: An anisotropic Bragg diffraction is studied applying simple design expressions to a tilt type in which an acoustic wave is launched a little off the [110] axis.
Abstract: Noncollinear acoustooptic tunable filters using TeO(2) crystals are described. An anisotropic Bragg diffraction is studied applying simple design expressions to a tilt type in which an acoustic wave is launched a little off the [110] axis. Tuning property, filter bandwidth, angular aperture, required acoustic power, deflection angle, divergenceless configuration, and rapid spectrum scanning have been discussed. These filter properties have been confirmed with measurements using three kinds of filter devices: a basic type, an acoustically enhanced type, and a large angular aperture type. A 5-A bandwidth at 4000 A was obtained by slow scanning. A 32-A separation at 4000 A was observed by a rapid scanning of 0.5 msec throughout the visible region with an extremely low electric drive power.
106 citations
TL;DR: In this article, the authors examined both the refracted beam and the beam due to Bragg scattering inside the periodic medium and found that the diffraction efficiency was smaller than that accounted for by previous approaches using a single incident plane-wave model.
Abstract: Analytical and numerical results are given on the diffraction of optical beams by a periodically modulated dielectric medium, which represents a thick hologram or an acoustic column. By using a rigorous representation for the field of a realistically bounded beam incident at a Bragg angle, we examine both the refracted beam and the beam due to Bragg scattering inside the periodic medium. The Bragg-scattered beam is formed by continuous coupling of energy from the refracted beam into the Bragg-scattered wave. As the Bragg-scattered wave also couples part of its energy back to the refracted wave, the continuous coupling of energy back and forth between these two waves results in a diffusion of energy over a wide region. For a sufficiently thick modulated layer, both the refracted and the Bragg-scattered beams split into two beams. Because of this distortion of the beam profiles, the diffraction efficiency is found to be smaller than that accounted for by previous approaches using a single incident plane-wave model.
67 citations
01 May 1976
TL;DR: In this paper, the authors summarized the important role of ZnO films in their application to surface acoustooptic devices on non-piezoelectric substrates.
Abstract: Studies of ZnO films which have been performed at Tohoku University are summarized to describe the important role of ZnO films in their application to surface acoustooptic devices on nonpiezoelectric substrates. The ZnO film has been confirmed experimentally as one of the most suitable materials for SAW transducers which can generate surface acoustic waves with power enough to attain the maximum diffraction efficiency in surface acoustooptic devices on nonpiezoelectric substrates in VHF and higher frequencies. It has also been confirmed to be useful as an optical waveguide which is suitable for use as the interaction medium in surface acoustooptic devices.
65 citations
TL;DR: The guided acoustooptical interaction on the (100) plane of GaAs is investigated as a function of waveguide thickness type of mode, acoustic frequency, direction of acoustic wave propagation, and substrate refractive index to indicate best efficiency.
Abstract: The guided acoustooptical interaction on the (100) plane of GaAs is investigated as a function of waveguide thickness type of mode, acoustic frequency, direction of acoustic wave propagation, and substrate refractive index Our calculated results indicate that best efficiency is obtained for TE0 → TE0 optical modes and for acoustic surface wave propagating along the 〈011〉 direction at a waveguide thickness close to cutoff Under these conditions, approximately 75 mW of acoustic power is required for 100% diffraction. For a transducer aperture giving 50 Ω of radiation resistance, the rf bandwidth of the diffraction is limited essentially by the frequency bandwidth of the interdigital transducer. A comparison of the calculated results with experimental data at 1.06-μm optical wavelength is also given.
50 citations
TL;DR: In this paper, algebraic expressions for the diffraction efficiency of a holographic grating recorded in a thick pure-phase material with a nonlinear exposure response for readout at the second-order Bragg angle were derived.
Abstract: Algebraic expressions are derived for the diffraction efficiency of the first and second orders of a holographic grating recorded in a thick, pure-phase material with a nonlinear exposure response for readout at the second-order Bragg angle. The results demonstrate the importance of double diffraction by the fundamental grating as well as diffraction by the harmonic grating in producing the second order. It is shown that the strong cross coupling between two gratings constructed in the same emulsion with a common construction angle is a limiting case of the double diffraction that occurs in single gratings. Experimental results from gratings constructed in dichromated gelatin are presented to verify the theory.
50 citations
TL;DR: In this paper, the amplitude of the first-order diffracted wave and the diffraction efficiency for an attenuated sinusoidally modulated grating were calculated using suitable approximations.
Abstract: Based on the theory of coupled waves the amplitude of the first-order diffracted wave and the diffraction efficiency respectively is calculated for an attenuated sinusoidally modulated grating using suitable approximations. Solutions for absorption, lossless dielectric, and mixed holograms in transmission and reflection are given. It is shown that the attenuation acts as a decreasing factor of the effective thickness of the storage medium. A deviation of Bragg-angle incidence shows an increasing and shifting of the secondary minimum and maximum values related to the normalized maximum value caused by attenuation.
31 citations
TL;DR: In this article, the possibility of making perfectly conducting rectangular-groove gratings perfectly blazed simultaneously in both polarizations is investigated and numerous efficiency curves are given, however, these curves are unfortunately greatly modified if finite conductivity is taken into account.
Abstract: The possibility of making perfectly conducting rectangular-groove gratings perfectly blazed simultaneously in both polarizations is investigated and numerous efficiency curves are given. Attention is given to the fact that these curves are unfortunately greatly modified if finite conductivity is taken into account.
27 citations
TL;DR: In this paper, a waveguiding layer displaying great photorefractive sensitivity has been formed by diffusion of iron into LiNbO3 by intersecting guided beams of red light from a He-Ne laser.
Abstract: Optical waveguiding layers displaying great photorefractive sensitivity have been formed by diffusion of iron into LiNbO3. Thick phase gratings of greater than 50% diffraction efficiency have been formed within such waveguiding layers by intersecting guided beams of red light from a He-Ne laser. By writing the gratings in a sample heated to 160°C, fixed gratings of about 1% diffraction efficiency have been produced. Modulation of the diffracted beam by electro-optic deflection of the input beam has been demonstrated.
24 citations
TL;DR: This section was established to reduce the lead time for the publication of Letters containing new, significant material in rapidly advancing areas of optics judged compelling in their timeliness.
Abstract: This section was established to reduce the lead time for the publication of Letters containing new, significant material in rapidly advancing areas of optics judged compelling in their timeliness. The author of such a Letter should have his manuscript reviewed by an OSA Fellow who has similar technical interests and is not a member of the author's institution. The Letter should then be submitted to the Editor, accompanied by a letter of endorsement from the OSA Fellow (who in effect has served as the referee and whose sponsorship will be in dicated in the published Letter) and A COMMITMENT FROM THE AUTHOR'S INSTITUTION TO PAY THE PUBLI CATION CHARGES. The Letter will be published without further refereeing. The la test Directory of OSA Mem bers, including Fellows, was published in the Spring 76 issue of Optics News.
20 citations
TL;DR: In this article, the profile of the hologram grating is described considering the absorption of the recording medium and its diffraction efficiency is calculated for special cases using the coupled wave theory.
TL;DR: In this paper, a holographically recorded 2 mm gratings having peak diffraction efficiencies in excess of 50% and angular selectivities less than 2 mrad by intersecting guided waves in a sample of photorefractive LiNbO3.
Abstract: Thick phase gratings have a variety of possible uses as device components in integrated optical systems. The applications make use of one or more of the unique properties of these gratings: high diffraction efficiency, good angular selectivity, and straightforward fabrication. In planar waveguides, the diffraction efficiency and angular selectivity desired for a particular application determine the length of the grating along the waveguide surface. We have holographically recorded 2 mm gratings having peak diffraction efficiencies in excess of 50% and angular selectivities less than 2 mrad by intersecting guided waves in a sample of photorefractive LiNbO3. Such gratings provide the central element in a number of actual and contemplated waveguide devices, including mirrors, beam splitters, lenses, switches, modulators, and interferometers.
TL;DR: An analysis of the diffraction efficiency of photorefractive holograms in ferroelectric crystals was shown to provide a novel technique for determining the nature and magnitude of the equivalent electron drift field.
Abstract: An analysis of the diffraction efficiency of photorefractive holograms in ferroelectric crystals is shown to provide a novel technique for determining the nature and magnitude of the equivalent electron drift field. For a Fe‐doped lithium niobate crystal (0.05% per mole) we find that the total field consists of an intensity‐independent internal field of 8.5 kV/cm and a photogenerated field given by the conversion factor 1.4 ×106 V cm/W.
TL;DR: It is shown experimentally that for high exposure, higher order Bragg diffraction by volume holograms is dominated by the nonlinear refractive index modulation and the application of nonlinear modulation to the construction of a high frequency volume-grating waveguide coupler is proposed.
Abstract: We have shown experimentally that for high exposure, higher order Bragg diffraction by volume holograms is dominated by the nonlinear refractive index modulation and proposed the application of nonlinear modulation to the construction of a high frequency volume-grating waveguide coupler
TL;DR: In this article, a relief-type grating made by the etching has a high diffraction efficiency (∽15%) and is analyzed by a Fourier expansion method under some assumptions.
TL;DR: In this article, a simple theory is presented to show the convolution process of two acoustic surface waves (ASW) has been obtained by the acousto-optical diffraction of an optical wave in an As2S3 waveguide.
Abstract: Convolution of two acoustic surface waves (ASW) has been obtained by the acousto‐optical diffraction of an optical wave in an As2S3 waveguide. A simple theory is presented to show the convolution process. Experimentally, very high acousto‐optical diffraction efficiency (93% at 3 mW of acoustic power) has been observed in the As2S3 waveguide. A triangular pulse was observed on the oscilloscope through an optical heterodyne detector when two rectangular ASW pulses were convolved with each other.
30 Dec 1976
TL;DR: In this article, a tutorial review is presented covering the real-time optical Fourier spectrum analysis of a wide band of electrical signals by means of acousto-optic diffraction.
Abstract: A tutorial review is presented covering the real-time optical Fourier spectrum analysis of a wide band of electrical signals by means of acousto-optic diffraction. Topics include frequency dispersion, spatial modulation, weighting functions, frequency resolution, sidelobe level, optical background level, acousto-optic bandshapes, normal and birefringent acousto-optic diffraction, figures of merit, diffraction efficiency, nonlinearities and spurious responses, dynamic range and output characteristics.© (1976) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, the behavior of a thick hologram was examined for gratings recorded holographically on Kodak 649F photographic plates by using a He-Ne laser, and it was shown that the contrast of the fringes decreases from the emulsion surface to the base.
Abstract: The behavior of a thick hologram is examined for gratings recorded holographically on Kodak 649F photographic plates by using a He-Ne laser. Interference fringes in the grating emulsions are observed with an optical microscope, and it is shown that the contrast of the fringes decreases from the emulsion surface to the base. The observed result is taken into consideration in applying the coupled wave theory, and numerical evaluations of a simple analytical expression are compared with measurements of the dependence of the diffraction efficiency on the angle of incidence for the amplitude and phase hologram gratings, and the amount of the decrease in the grating modulation is found.
Patent•
05 Oct 1976TL;DR: In this article, an acoustic wave deflection frequency range is utilized which will result in no more than a predetermined maximum variation of diffraction efficiency and which covers the Bragg-tolerance ranges for all wavelengths used.
Abstract: Apparatus and method are disclosed for diffracting light beams of different wavelengths to form a color image without achromatizing optics. An acoustic wave deflection frequency range is utilized which will result in no more than a predetermined maximum variation of diffraction efficiency and which covers the Bragg-tolerance ranges for all wavelengths used. Because the different wavelength beams will scan at different speeds (covering the same angular deflection during different scan times) intensity modulating information for each wavelength is impressed upon an acoustooptic modulator in the light path at different appropriate rates and during different appropriate periods during the scan. The modulating information for each wavelength is impressed upon the modulator only during that respective time period in which the deflection frequency is within a range that will result in angular diffraction ranges which match for all beams.
Patent•
01 Jun 1976TL;DR: In this article, a device for measuring light incident on an image forming optical system, making use of a plural number of the diffraction element, is presented, where the light beam is measured by a light detecting means in the same way as in this case, while the non diffracted light beam advances along the above mentioned optical axis.
Abstract: The present invention relates to a device for measuring light incident on an image forming optical system, making use of a plural number of the diffraction element. The plural number of the diffraction elements are respectively provided in the optical path of the image forming optical system. Further the plural number of the diffraction elements respectively present a certain predetermined area. The plural number of the diffraction elements, seen along the direction of the optical axis of the image forming optical system, are substantially only partially overlapped with respect to each other. The light beam incident on a diffraction element is divided into a non diffracted light beam and a diffracted light beam. Thus diffracted light beam is directed toward the light detecting means so as to be measured while the non diffracted light beam advances along the above mentioned optical axis. Consequently at the part at which the diffraction elements overlap each other, the non diffracted light beam led out of the preceeding diffraction element again enters the following diffraction element. This light beam is again divided into a non diffracted light beam and a diffracted light beam by means of the following diffraction element. The diffracted light beam is measured by a light detecting means in the same way as in the above mentioned case, while the non diffracted light beam advances along the above mentioned optical axis. Thus the light beam which passes through the overlapping parts is measured a plural number of times.
TL;DR: In this article, a strain-controlling film to change acoustic strain distributions in the interaction region between acoustic surface waves and optical guided waves is introduced to improve the Bragg-diffraction efficiency in surface-acoustic-optic devices.
Abstract: A strain‐controlling film to change acoustic strain distributions in the interaction region between acoustic surface waves and optical guided waves is introduced to improve the Bragg‐diffraction efficiency in surface‐acoustic‐optic devices. An improvement of about 2 orders of magnitude has been achieved in the efficiency of TM0‐TM0 diffraction at an acoustic frequency of 130 MHz in a 2.0‐μm ZnO‐film optical waveguide with a strain‐controlling film of a 1.5‐μm‐thick fused‐quartz film, as predicted by the theory.
TL;DR: Diffraction efficiencies as high as 15% have been measured for thick plane wave holograms consisting of grating arrays of oriented M centers in additively colored KCl.
Abstract: Diffraction efficiencies as high as 15% have been measured for thick plane wave holograms consisting of grating arrays of oriented M centers in additively colored KCl. The values obtained agree well with calculated estimates based on the induced birefringence and dichroism.
30 Dec 1976
TL;DR: In this article, a step-array-transducer in the UHF region is developed, employing a wedged intermediate medium to make up the precise steps, and the authors have successfully constructed a number of wideband steparray acoustooptic beam deflectors with total flexibility in interaction medium selection.
Abstract: The performance of an acoustooptic beam deflector depends on its bandwidth and diffraction efficiency with its acoustic delay time providing a trade-off possibility between resolvable spots and access time. Transducer power density considerations with present fabrication techniques place a limit on acoustooptic beam deflectors at 100 MHz bandwidth with 50% efficiency. It has been known for some time that the deflector efficiency bandwidth product can be improved with acoustic beam steering by stepped-array-transducers. However, a simple practical fabrication technique for the step-array-transducer in the UHF region is yet to be developed, due to miniature step dimensions. Employing a wedged intermediate medium to make up the precise steps, we have successfully constructed a number of wideband step-array acoustooptic beam deflectors with total flexibility in interaction medium selection. Typical parameters on our deflectors are 50% diffraction efficiency at 750 mW rf drive power, up to 250 MHz 3 db bandwidth (200 MHz 1.5 db), and 2mm by 30 mm optical aperture with PbMoO4 deflector body. That is a deflector of 2000 spots at 8.5 microsecond access time. Ultimate deflector bandwidth limit with this fabrication technique is estimated to be about 350 MHz.© (1976) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: The use of dichromated gelatin for holographically recording the component single frequency gratings of a high efficiency grating lateral shear interferometer is described.
Abstract: The use of dichromated gelatin for holographically recording the component single frequency gratings of a high efficiency grating lateral shear interferometer is described. Interferograms obtained using a grating lateral shear interferometer simultaneously having a diffraction efficiency of 30% in each of two shearing interferograms are presented.
TL;DR: In this paper, an accessory photovoltaic LiNbO3 crystal, highly iron doped and reduced, was used to enhance the photorefractive sensitivity and saturation of the diffraction efficiency.
TL;DR: It is shown that thick holographic gratings may exhibit significant amplitude and grating phase variations with thickness including amplitude sign reversal that strongly affect holographic grating recording and readout characteristics such as maximum possible diffraction efficiency and angular selectivity.
Abstract: Dynamic theory of volume holography is used to calculate the variations in the thickness direction of the hologram-constituting refractive-index modulation and the externally observable effects of these variations in electrooptic materials. It is shown that thick holographic gratings may exhibit significant amplitude and grating phase variations with thickness including amplitude sign reversal. These nonuniformities strongly affect holographic grating recording and readout characteristics such as maximum possible diffraction efficiency and angular selectivity. Thus a variety of grating applications will be affected by these nonuniformities.
TL;DR: The refractive index profile, the effective photovoltaic field, and the relative contributions of diffusion and drift are determined from experimental measurements for a lithium niobate holographic grating.
Abstract: A method for determining the refractive index profile of thick phase gratings in linear electrooptic crystals is presented. This method also determines the effective photovoltaic electric field and the relative contributions of diffusion and drift during hologram recording. The method requires only a knowledge of the modulation ratio during hologram recording and the fundamental and the higher-order diffraction efficiencies of the grating. As an illustration of the method, the refractive index profile, the effective photovoltaic field, and the relative contributions of diffusion and drift are determined from experimental measurements for a lithium niobate holographic grating.
TL;DR: An analysis describing the thermal behavior of a thin film subjected to a spatially modulated irradiation field shows that it is possible using a cw laser to establish a temperature field in such a film that maps the irradiation pattern with a resolution adequate for recording high quality holograms.
Abstract: This paper presents an analysis describing the thermal behavior of a thin film subjected to a spatially modulated irradiation field. The analysis shows that it is possible using a cw laser to establish a temperature field in such a film that maps the irradiation pattern with a resolution adequate for recording high quality holograms. Effects of the thermal properties of the film and substrate on such recording characteristics as linearity, sensitivity, and resolution are examined. A high diffraction efficiency recording technique based on the sublimation of a thin film situated on a constant temperature substrate is proposed as an example of the application of the analysis.