Showing papers on "Diffraction grating published in 1969"

Optical pulse compression with diffraction gratings

Abstract: The theory of the diffraction grating pair is developed by expanding the frequency dependence of the phase shift as far as the quadratic frequency term. The analogy between pulse compression and Fresnel diffraction is treated. The effect of the cubic phase term is discussed for ultrashort pulses having appreciable fractional bandwidth.

Theoretical and Experimental Investigation of a New Type of Blazed Grating

Abstract: A rigorous electromagnetic theory of the diffraction of light by blazed lamellar gratings has been developed. It is applied to calculate the diffracted power distribution of four gratings (R1 − R4) whose grooves have the following depths and widths (b,l) in units of grating period a: (0.433, 0.750), (0.333, 0.667), (0.250, 0.500), and (0.200, 0.400). All four gratings are theoretically blazed in the minus-first order for 30° incidence and for the wavelength equal to the grating period. The blaze is, however, broad band, and the minus-first-order theoretical power-conversion efficiency (P−1) for the most interesting grating, R3, exceeds 0.8, 0.9, 0.95, and 0.98 in the wavelength bands 0.84 a−1.49 a, 0.85 a−1.47 a, 0.87 a−1.43 a, and 0.98 a−1.31 a, respectively, for linearly polarized light. These surprising performances, which far exceed those obtainable with echelette gratings insofar as the incident light is linearly polarized, have been experimentally verified with the help of a microwave interference spectrometer, and point to the potential usefulness of blazed lamellar-reflection gratings in far-infrared spectroscopy.

Orotron—An electronic oscillator with an open resonator and reflecting grating

Abstract: The results are presented from a study of the orotron, a new electronic generator of the millimeter and submillimeter wavebands with a wide range of frequency tuning. An open resonator with a grating on one of its mirrors is used as the oscillatory system. The device is excited by passing an electron beam over the grating.

Nonuniform Sinusoidally Modulated Dielectric Gratings

Abstract: A simple, three-dimensional, holographic grating consists of a sinusoidally modulated dielectric slab. The assumption that the modulation index, δ, is constant is at most a first-order approximation. Usually, the light beams used in making the grating are attenuated inside the recording material, hence δ varies within the dielectric slab. From known solutions for the electromagnetic field diffracted by a uniform dielectric grating, solutions for the case when δ is not constant are found, first for a lossless and then for a lossy dielectric grating. The effective modulation index of the grating at exactly Bragg-angle incidence is given by the averaged value of δ over the slab thickness.

Diffraction Grating Spectroscopy

Abstract: The present state of grating spectroscopy is reviewed with special emphasis on the far ir. The review includes the discussion of the properties of diffraction gratings, the intensity distribution among different orders of echelette gratings, Wood anomalies, ir and submillimeterwave filters, detectors, grating spectrometers with thermal sources, rules for the construction of far ir and submillimeterwave grating spectrometers, diffraction at the monochromator slits, comparative performance of interferometers and grating spectrometers, and spectroscopy of far ir laser emissions. Extensive references are presented.

An Analytical Study of the Echelette Grating with Application to Open Resonators

Abstract: Reflection coefficients of various order diffracted waves are calculated for an echelette grating which finds important use as a component of suboptical resonators. The classical optics approach has been found to be inadequate for deriving reliable results for this configuration. Accurate solution of the boundary value problem associated with the echelette grating is derived by a new method. The results are useful for the design of suboptical resonators which use the echelette grating as a coupling mirror to achieve a single wavelength operation.

Diffraction Gratings in Phalacrid Beetles

Abstract: UNTIL this year a scarabaeid beetle, Serica sericea, was commonly cited as the only insect in which the iridescent colours were due entirely to diffraction rather than to interference. It is now known, however, that the iridescence of many other scarabaeid beetles1 in both the tribes Sericini and Melolonthini is due to diffraction gratings, as is that of a few beetles of the family Carabidae1. In addition, the iridescent colour of the stridulatory file on the third abdominal segment of wasps of the family Mutillidae is now known to be produced entirely by diffraction2.

Optical systems having spatially invariant outputs

Abstract: This disclosure describes optical systems that have output beams that are spatially invariant to the angle of incidence upon a certain rotatable surface forming a part of the systems, and can be used to select the wavelength of the output of an optical source, such as a laser cavity, or to aid in measuring the reflectance of a material in reflectance spectroscopy. The optical systems comprise various combinations of plane mirrors and plane diffraction gratings (or sample surfaces), in some embodiments, spherical mirrors. The plane mirrors, plane gratings and spherical mirrors are either rotated or fixed in space in accordance with a particular embodiment. The moveable suitable movement mechanism, such as a micrometer. By rotating the shaft of the micrometer to a particular incidence angle, the frequency of the output of a laser cavity can be selected. Alternately, the reflectance of a material can be observed for a particular angle. In either case, the output beam remains spatially invariant as the position of the shaft and its attached elements is changed.

Diffraction grating interferometer

Abstract: An interferometer, and preferably an infrared laser interferometer, employing a single, reflecting diffraction grating operating as both the beam splitter and the reference surface. A collimated beam from the radiation source is directed onto a surface of the diffraction grating and is diffracted into two separate beams, namely a test beam and a reference beam. The test beam is directed to the test optical system and is then reflected back, as a return beam, from the test optical system to the diffraction grating, at an angle such that a diffracted return beam is produced by the diffraction grating that coincides with the reference beam. An interference pattern is produced between the reference beam and the diffracted return beam, that can be observed, at the plane of observation, visually or recorded with an image recording device.

A new plane grating monochromator with off-axis paraboloids and curved slits.

Abstract: A design for a new plane grating monochromator is described. The system employs a symmetrical configuration of off-axis paraboloids for both the collimator and camera mirrors. The entrance and exit slits are mounted on the same side of the grating and are curved in order to eliminate wavelength errors due to spectral line curvature. There is, in fact, a remarkable coincidence between the curvature which is required to avoid wavelength errors and the curvature which is required to obtain equal curvatures in the object and image planes. Ray tracing calculations for a symmetrical configuration of off-axis paraboloids show that the image of a curved slit with a length equal to 0.05 times the focal length of an f/5 mirror is diffraction limited for wavelengths λ > 0.2 μ.

Diffraction type mosaic system

Abstract: MEANS AND METHOD FOR PRODUCING CO-ORDINATE SPECTRA FROM RANDOMLY ARRAYED MOSAICS OF DIFFRACTION GRATINGS BY USING CURVED-LINE GRATINGS, AND FOR INCREASING THE EFFICIENCY OF SPECTRUM PRODUCION BY CIRCULAR GRATINGS BY USING ARRAYS OF PARTS OF THE GRATINGS IN SELECTED STRUCTURAL ORGANIZATION

A double pass spectrometer for the far infrared.

Abstract: A far ir spectrometer has been built which uses a double pass optical system to increase the spectral dispersion. Because of the energy limitations in this spectral range, this means of increasing the dispersion is an efficient way to improve the resolving power of a grating monochromator. The same optical system is also used to advantage in a lamellar grating interferometer where the increased dispersion improves the performance at higher frequencies. Consideration is also given to instrument errors and signal noise which can affect, and in some cases limit, the present performance of a far ir Fourier interferometer.

Photoelectric optical grating

Abstract: An index grating for use in measuring apparatus in which relative movement between the index grating and a scale grating is monitored, consisting of a regular series of alternate transparent and opaque regions, the opaque regions constituting parts of a solid state photocell. There is also described a reading head incorporating such an index grating.

Optical projection system with enhanced color resolution

Abstract: In light value projection apparatus employing a medium deformable by a scanning electron beam into a plurality of diffraction gratings, each grating controlling the light of a respective primary color, improved resolution of magenta light is achieved by furnishing only red and blue video signals below a selected cutoff frequency to red and blue modulators respectively, and by furnishing only the red and blue video signals above this frequency or the luminance signals above this frequency, to a magenta modulator. The magenta modulator carrier frequency is selected to exceed the beat frequency between the red and blue diffraction gratings. The red, blue and magenta modulator output signals are combined bore being applied to electron beam deflection plates.

Observation and measurement of surface relief of diffraction gratings using electron microscopy techniques

Abstract: Two methods for the direct presentation and precise determination of surface relief of diffraction gratings are described, both of which utilize metallic replication techniques. A comparison of the results obtained is made with an interferometric measuring technique and the results are in agreement to within the errors of measurement. Surface irregularities of 2 nm have been measured from the electron micrographs of the surfaces of diffraction gratings, but the methods are applicable to any similar surface study.

Wavelength errors in spectrographs. I: the effect of surface irregularities in camera mirrors.

Abstract: High–dispersion astronomical coude spectrographs frequently give lower–precision radial velocities than expected. This is explained in part in terms of the variable spectral shifts along the plate produced by a camera mirror with zonal imperfections. For a mirror with a sinusoidal zonal irregularity, the standard deviation in the radial velocity depends inversely on the angular dispersion and size of the grating or prism and directly on the amplitude of the surface fluctuation. For a 300–mm grating with 1200 lines/mm used in first order at λ = 0.5 μm, a standard deviation of 0.06 km/sec is obtained for a single measurement if the surface has a peak–to–valley fluctuation of 1/20 wavelength of green light.

Method and apparatus for magneto-optical reading of superimposed magnetic recordings

Abstract: Superimposed tracks of magnetic recordings are read by use of a magneto-optic transducer. The recordings are on magnetic tape which is passed in close proximity to a magnetic thin-film layer coated to the reflecting side of a prism. The superimposed recordings on the tape are transferred in bulk to the magnetic thin film. Linearly polarized, monochromatic, collimated, substantially coherent light is passed into the prism and reflected from the back of the prism and out the other face of the prism. At the reflecting surface, the linearly polarized light experiences a rotation of its plane of polarization because of the magnetic field stored in the thin film. The rotation is in accordance with the well-known magneto-optic Kerr effect. The rotated light passes out of the prism and through an analyzer. The analyzer is adjusted to pass only that light which was given a particular rotation by the magnetic thin film. Because recorded tracks are closely spaced, the light emitted from the analyzer is similar to light passing out of a diffraction grating. This light passes through a lens which forms a Fraunhofer diffraction pattern of the light passed by the analyzer at the focal plane of the lens. A Fraunhofer diffraction pattern for each orientation of recorded tracks appears at the focal plane. A spatial filter is placed at the focal plane of the lens and rotated to align itself with the Fraunhofer pattern associated with one orientation of tracks. The spatial filter passes only the light of the pattern which the filter is aligned with. This light is imaged onto a detector system to read out the information recorded in tracks orientated to produce the filtered pattern.

The use of an improved diffraction grating interferometer.

Abstract: A conventional schlieren system was converted into a Kraushaar interferometer by the addition of matched diffraction gratings as the beam splitting and recombination elements. Optical quality of the added features of this installation were shown to be not a limiting factor, but the optical platform must be isolated well for good results. Basic optical theory applicable to this device is summarized. Several aspects are indicated which enhance the fringe or image quality. This device has been used to find the surface pressures and flow field structure around some simple two-dimensional airfoil shapes. Comparison of these results with calculations indicates good agreement between the diffraction grating interferometer data and analytical data.

Noncontacting method of measuring strain

Abstract: A noncontacting method for measuring strain in a workpiece wherein strain measurements are based on an optical diffraction grating produced by interfering beams from a giant-pulse laser thereby enabling the thermal engraving of diffraction gratings on irregularly shaped surfaces.

Hologram reproduction system using an optical grating

Abstract: A holographic image reconstruction system in which holographic light amplitude and phase information are resolved spearately for reconstruction of the original hologram. The amplitude component is separately detected and reproduced on a cathode ray tube or other electronically addressable optical display. The image of the amplitude component is projected through an external optical grating onto a film for recording or onto a real time imgaing system. Phase information from the holographic data is separately detected and superimposed on the amplitude data by varying the phase of the shadow image of the optical grating on the amplitude image. Phase moduflation of the image of the grating is accomplished by modulating the aperture or angle of the lens which images the amplitude pattern through the grating onto the film, or by modulating the grating itself.

Apparatus for determining the relative movement of an object with the use of an optical grating rigidly secured to the object

Abstract: The invention relates to an apparatus for determining the relative movement of an object with the use of an optical grating rigidly secured to the object, in which energy emanating from a source of energy interacts with the grating and then is supplied to a system which is sensitive to this energy and converts it into an electric signal which is a periodic function of the movement of the objects characterized in that a second optical grating the periodic direction of which is at right angles to that of the first grating covers this first grating and is substantially coplanar with it.

A double monochromator for the extreme ultraviolet.

Abstract: The optical design of a double monochromator suitable for use in the extreme uv is presented. The system employs fixed entrance and exit slits and two concave diffraction gratings which are rotated to vary the wavelength at the exit slit. Adjustment of the optical parameters and use of symmetry produces an approximate focusing condition accurate to fourth order in grating rotation. The defocusing at the exit slit is comparable to the Seya mounting. The astigmatism is calculated and the transmission properties briefly discussed.