Showing papers on "Diffraction grating published in 1974"

Geometric theory of the grating

Abstract: Geometric theory of the grating is developed, with special emphasis on the relation between the properties of holographic gratings and those of mechanically ruled gratings. The theory is applicable to practically all types of holographic and mechanically ruled gratings, including aspheric gratings. General expressions are given for the effective grating constant, the grating equation, the focal curves, and the light-path function. Possible applications of the theory to the design of aberration-corrected gratings are also described.

White Light Extended Source Shearing Interferometer

Abstract: A grating lateral shear interferometer is described that can be used with a white light source. The use of the interferometer with certain types of extended sources is also demonstrated.

Gigahertz tunable waveguide CO2 laser

Abstract: A sealed‐off cw waveguide CO2 laser has been continuously tuned over 1.2 GHz on a single transition at 10.6 μm. The laser consists of a 9.5 cm×1.0 mm square discharge tube fabricated from polished BeO slabs. Line selection is achieved with a diffraction grating and tuning is accomplished by piezoelectric control of the resonator length.

Optical indicia marking and detection system

Abstract: An optical marking system which utilizes tags that are formed from multiple diffraction gratings, which gratings differ in orientation and number of lines (frequency) in accordance with the coded information desired on the tags. A monochromatic light source illuminates a diffraction grating tag, with reading of the coded information on the tag being accomplished by sensing the reflected light which is projected as images in a Fraunhofer plane. Retroreflective elements are provided in the optic train as a means for stabilizing the direction of reflection from the diffraction gratings such that the reflections are somewhat independent of the tilt angle of the tag with respect to the illuminating light.

A Detailed Theoretical Study of the Anomalies of a Sinusoidal Diffraction Grating

Abstract: Theoretical counterparts are presented for the experimental efficiency curves obtained by Hutley and Bird in the visible region for a holographic grating covered consecutively with films of silver, aluminium and gold. It is thus shown that the recently developed formulation of Maystre, which takes into account the finite conductivity of the grating surface, gives results in quantitative agreement with experiment. This not only validates the theory, but also demonstrates that the difficulties associated with profile determination and oxide films, which have in the past led some experimenters to renounce the visible region and perform measurements on millimetre-wave gratings, are not in fact insuperable. It is also shown that only a theoretical model which takes into account groove depth effects can hope to predict accurately the locations of regions of enhanced energy absorption by gratings.

Linear pressure tuning of a multielement dye laser spectrometer.

Abstract: Construction details and operating characteristics are given for a narrowband pulsed dye laser system, pumped by a nitrogen laser, that offers very linear reproducible frequency tuning over continuous ranges of 150 GHz and more, at a bandwidth down to 25 MHz. A diffraction grating in Littrow configuration, a tilted Fabry-Perot interferometer inside the cavity, and an optical external confocal filter interferometer are the wavelength-selective elements. Simultaneous scanning of these elements is accomplished without mechanically moving parts by changing the gas pressure in an enclosing chamber.

Focusing Errors in a Collimating Lens or Mirror: Use of a Moiré Technique

Abstract: The Fresnel diffraction pattern of a grating periodically gives an exact reproduction of the grating. By superposing a second grating on such an image, we form a moire pattern that depends upon the degree of parallelism of the incident beam. We present here the possibility of using this technique for studying the focusing errors in a collimating lens or a mirror.

Design of holographic concave gratings for Seya-Namioka monochromators

Abstract: The theory of the holographic grating is applied to the design of aberration-corrected holographic concave gratings for use with Seya–Namioka monochromators. A method of determining the proper recording parameters is described. The performance of gratings that would be produced by use of the proper recording parameters is evaluated in terms of the magnitude of the aberration terms and the degree of spread in spot diagrams. The results indicate that properly designed holographic concave gratings show much improved performance over mechanically ruled concave gratings.

Portable prism-grating coupler

Abstract: There is disclosed a portable, reusable prism coupler which, unlike conventional prism couplers, need not be of higher refractive index than that of the thin-film waveguide into which the light is to be introduced. Structurally, there is fabricated on the surface of the prism which is disposed nearest to the thin-film waveguide a fixed optical grating. Grating periodicity is selected such that a beam of light incident on the grating inside the prism is internally diffracted essentially completely in a backward direction. By properly selecting the angle of incidence of the light beam on the grating, the evanescent field of the diffracted portion of the beam can be phase-matched and coupled through the separation between the prism and the waveguide to the various propagating modes therein. Since the refractive index of the prism is essentially uncritical, the arrangement should be particularly useful for coupling light into and out of thin-film waveguides formed of materials having relatively high refractive indices (e.g., gallium arsenide). The arrangement may likewise be useful for the large scale, nondestructive testing of thin-film waveguides as they are fabricated on the production line.

Leaky corrugated optical waveguide device

Abstract: Diffracted leaky optical waves are coupled out of a thin film optical waveguide device having one surface which is periodically thickness-modulated or corrugated to form an optical diffraction grating. The waveguide device is constructed such that the average thickness of the waveguide in the complex refractive index of the waveguide or one of the layers surrounding the waveguide is varied when an external power source applied to the device is varied and thereby, a parameter of the leaky wave in accordance with the variable power source. In one embodiment, the waveguide is made of light amplifying material which is suitably excited to produce lasing action and cause an optical wave to propagate in the waveguide. The variable parameter in this case is the wavelength of the leaky wave, and the leaky wave is always normal to the plane of the diffraction grating. Consequently, a tunable laser is provided. In a second embodiment, no lasing occurs, but instead, an external light source is used to cause an optical wave to propagate in the waveguide. The parameter which is varied is the angle between the leaky wave and the normal to the diffraction grating, the wavelength of the leaky wave remaining constant.

Concave diffraction grating and a manufacturing method thereof

Abstract: A tool for ruling grating grooves is reciprocated on a diffraction grating blank with the tool being restrained within a plane inclined at an arbitrary angle relative to a plane lying in contact with one point on a spherical concave of the diffraction grating blank. Translation for a variable pitch-groove spacing which changes as a function of the groove number or groove position is imparted to the diffraction grating blank in interlocking relationship with the reciprocation, thereby mechanically ruling the desired sphere of the grating blank with the grating grooves, whereby a concave diffraction grating which forms diffracted light of a specific wavelength into a completely stigmatic image at high diffraction efficiency can be manufactured.

Lasing characteristics of seventeen visible-wavelength dyes using a coaxial-flashlamp-pumped laser.

Abstract: The performance and tuning characteristic of organic dye lasers were measured using commercially available coaxial flashlamps as the pumping source. Tuning by a diffraction grating permitted continuous coverage of the 4200–7500-A region at up to 0.6% tuned output energy efficiency. Preliminary results with a 600-J Marx-Bank coaxial laser at 4500 A show 1% efficiency and single-pass unsaturated gain greater than 20 at 4500 A.

Selectively etched diffraction gratings in GaAs

Abstract: Selective etching techniques are described which have been utilized to fabricate V‐groove diffraction gratings with spatial frequencies greater than 4000 lines/mm in {100} surfaces of GaAs.

Simultaneous exposure and development technique for making gratings on positive photoresist

Abstract: A simultaneous exposure and development technique for forming diffraction gratings and recording holograms in positive photoresist is described. This technique not only reduces the exposure time significantly, but is also able to produce gratings with deep grooves and sharp ridges. With the photoresist placed in a liquid‐filled prismlike container, the smallest period obtainable by this method is reduced by a factor equal to the index of refraction of the liquid.

Optical grating evaluator: a device for detailed measurement of diffraction grating efficiencies in the vacuum ultraviolet.

Abstract: A device for detailed measurement of diffraction grating efficiencies and over-all performance in the VUV has been designed and constructed at the Naval Research Laboratory. The system employs semiautomated mechanisms to scan the face of the grating with a narrow monochromatic beam, and an efficiency map of the grating surface is produced on a strip chart recorder. Grating efficiency in the various diffracted orders and intensity of light scattered between orders may also be measured. A unique feature is the ability to determine the angle and effectiveness of grating blaze and variations in blaze under different conditions of illumination.

Color image intensification and projection using deformable mirror light valve

Abstract: A color image intensifier and projector includes a reflective light valve lamination having, in order, a flexible conductive mirror, a deformable layer, a photoconductive layer, a transparent conductive layer, and a plurality of optical diffraction gratings each for a different color An electric potential is applied across the flexible conductive mirror and the transparent conductive layer to bias the photoconductive layer When an input colored image is projected through the gratings to the photoconductive layer, the resulting electric fields cause the deformable layer and flexible conductive mirror thereon to be deformed in accordance with the colored image as modified by the diffraction gratings A Schlieren optical system is included to direct light from a source to the flexible conductive mirror, and to collect reflected light and direct it through a fourier transform plane to a utilization plane A color-decoding spatial filter is located in the fourier transform plane to recreate the color image at the utilization plane

An interference technique for the measurement of in-plane displacements of opaque surfaces

Abstract: A laser interferometer system is used to record two mutually perpendicular diffraction gratings on a photoresist coated specimen. When either grating is re-illuminated by the fringe pattern used to form it, real-time observations can be made of moire fringes corresponding to surface displacements which occur as a tensile load is applied to the specimen. The technique has been used to study the in-plane deformations of carbon-fibre composites, and typical results are given.

Piezoelectrically driven optical grating assemblies

Abstract: An optical grating assembly comprises a piezo-electric substrate which supports on two opposite faces thereof respective metallic layers. One of these faces of the substrate also carries a grating either formed in that face, in the metal layer supported by that face, or in a resin layer carried by that face. Application of a variable voltage between the metal layers sets up an electric field of variable strength in the substrate and this results in the pitch of the grating being variable due to the piezo-electric nature of the substrate.

Focalization process of spherical concave diffraction gratings

Abstract: Spectrometric gratings formed by holographic techniques are disclosed. The gratings are employed in monochromator mounts of the type in which fixed entrance and exit slits are combined with simple rotation of the grating to scan the spectral range of interest, the angles of incidence and diffraction and the positions of the slits being so related that the mounts are characterized by improved optical performance due to phase balancing and improved focussing properties according both to geometrical and diffraction theories. The parameters involved in the holographic formation of the gratings, specifically the angularities and positions of the point sources forming the holographic image of the grating lines, are specifically related to the characteristics of the mount as to improve further their optical characteristics, particularly with respect to mounts either employing "normal" (i.e., relatively small) angles of incidence with large grating apertures or employing grazing incidence (i.e., for use in the far ultraviolet region).

Reflecting diffraction grating for minimizing anomalies

Abstract: In a reflecting diffraction grating having a plurality of grooves for light diffraction, each groove being formed by a reflecting surface and a rear surface, the rear surface is so formed that light coming thereupon is subjected to an irregular reflection.

Change of blaze wavelength as a function of position on the surface of a concave grating

Abstract: Conventional ruling of a concave diffraction grating with blaze angle constant relative to the optical axis produces a grating whose blaze wavelength changes continuously with displacement across the face of the ruled area. A simple explanation of the effect is given in terms of geometrical optics, and quantitative expressions are developed that relate the expected blaze-wavelength shift to the grating constant and aperture ratio. Results are compared with experimental efficiency measurements, and the magnitude of the effect in a typical grating is discussed.

Gratings for integrated optics by electron lithography.

Abstract: The electron lithographic fabrication of high quality diffraction gratings with periods in the 0.25-microm < a(o) < 1.5-microm range is reported. The negative electron resist employed is a copolymer of glycidyl methacrylate and ethyl acrylate with a sensitivity about 15 times better than that of poly(methyl methacrylate), a positive resist. A new scan generator with linearity accurate to 1 part in 10(4) and locked onto the 60-Hz power supplies is described. Gratings with up to 3000 lines were fabricated with long range order deltaa(o)/a(o)

Temporary gratings on germanium

Abstract: Diffraction gratings have been formed on the surface of germanium using two beams from a ruby laser inclined at an angle to each other. Grating spacings from 2 to 20 μm have been formed that appear to be present only during the illumination and no visible damage is observed. Subsequent illumination with a single beam produces no observable diffracted beams. Permanent gratings in damaged areas can be produced with more intense beams. The intensity of a diffracted order appears to depend on the product of the intensities of the incident beams. Several applications of the temporary grating are suggested.

Etalon/Grating Synchronized Scanning of a Narrowband Pulsed Dye Laser

Abstract: A computer compatible digital scanning system has been developed to simplify the controls of a narrowband pulsed tunable dye laser so that operation is analogous to scanning a spectrometer. The system is an accessory to the nitrogen laser-pumped DL-Series dye laser which incorporates both grating and etalon as the wavelength selecting elements. The grating is rotated with a mechanical sine drive so that wavelength response is linear. Linewidth of the laser without etalon is 0.1A and scanning is achieved with a stepping motor. Inserting an etalon into the cavity reduces the linewidth to 0.01A and tuning is achieved by tilting the etalon. However, since the etalon wavelength change depends on the grating wavelength and decreases as the square of the tilt angle, wavelength synchronization to the grating becomes difficult. In our system a digital computation accurate to 0.01% linearizes the etalon response to match that of the grating. Single scans of 3A and multiple scans of 30A can be achieved without loss of wavelength synchronization. Analog and digital wavelength readout to 0.01A and computer compatibility are included. System details and sample data are presented.

Injection laser with a diffraction grating in its resonator

Abstract: An investigation was made of the emission spectra of an injection laser with a selective feedback produced by a reflecting diffraction grating. The spectral characteristics of the laser were improved when the natural resonator was replaced with an antireflection coating and when a diode with a conventional resonator was used. A pulsed power in excess of 6 W was obtained at 300°K in a band not wider than 0.1 nm in the first case and 0.45 W in a band not wider than 0.01 nm in the second case.

Electro-optic modulator

Abstract: An electro-optic modulator used to modulate coherent light beams by the application of an electric potential. It combines a Fabry-Perot etalon and a diffraction grating in a single unit. An etalon is constructed with an electro-optic material between reflecting surfaces. A voltage applied between alternate, spaced-apart electrodes of a metal grid attached to one reflecting surface induces a diffraction grating in the electro optic material. Light entering the etalon is diffracted, reflected and efficiently coupled out.