Interference Grating Research Articles

In-plane displacement measurement using objective speckles in photorefractive two-beam coupling: effect of multiple exposures

A technique is proposed for the real-time measurement of in-plane displacement utilizing objective speckles and two-beam coupling in a photorefractive BaTiO 3 crystal. Speckles generated by a diffuse object in free-space geometry are used as the signal in two-beam coupling. The set-up is such that the phase shift between the refractive index grating and the interference grating is + π 2 (amplification mode). Due to the in-plane displacement, Young's fringes are obtained with a bright speckle background as a result of the signal amplification and beam fanning. The slow process of two-beam coupling amplification in a BaTiO 3 crystal is exploited for recording multiple exposures. This method of recording multiple exposures provides a simple and convenient way of analyzing the rigid body motions with enhanced accuracy by sharpening the fringes and with acceptable contrast. Theory has been developed to obtain the intensity distribution in the fringes formed in real time at the observation plane. Experiments have been conducted to show the validity of the theoretical results. Good agreement is established between the theory and the experiments.

Dynamic interference grating—new technique for the study of non-crystalline films†

The results are presented of a dynamic interference grating (DIG) photocurrent study in a-Si:H films. A model and theoretical analysis are given. DIG photo-current as a function of both temporal and spatial frequency Iω (ω), Iω(K) have been studied. The experimental curves are in good agreement with the calculated ones. They are used to determine the magnitudes of the Maxwell relaxation times and diffusion lengths for both electrons and holes. The effect of light intensity on the photocurrent is shown to be due to quadratic recombination.

Moving grating technique: A new method for the determination of electron and hole mobilities and their lifetime

A new technique to determine the mobilities and lifetime of photogenerated electrons and holes in semiconductors relies on the short circuit current that is induced perpendicularly to a moving interference grating. Theoretical expressions for the short circuit current are derived that relate the carrier mobilities and their lifetime to the velocity and spatial period of the grating. The technique has been implemented and was successfully applied to a-Si:H.

Thermodiffusion in polymer solutions as observed by forced Rayleigh scattering

Thermodiffusion, the cross coupling between temperature and concentration, is studied in dilute polymer solutions by forced Rayleigh light scattering. First a spatial temperature grating is created within the solution by absorption of an optical interference grating and subsequently a concentration grating builds up. The time-dependent diffraction efficiency of both gratings is described by a phenomenological model from which the thermal diffusivity, the ordinary diffusion coefficient, and the thermodiffusion coefficient are obtained without the need for absolute intensity measurements or calibration with a known standard. No labeling of the polymer chains with photochromic dyes is required. Experimental details and potential pitfalls are discussed. Measurements are carried out on polystyrene in ethyl acetate and the obtained values compare well with data taken from the literature.

Modulation transfer function measurement technique for small-pixel detectors

A modulation transfer function (MTF) measurement technique suitable for large-format, small-pixel detector characterization has been investigated. A volume interference grating is used as a test image instead of the bar or sine wave target images normally used. This technique permits a high-contrast, large-area, sinusoidal intensity distribution to illuminate the device being tested, avoiding the need to deconvolve raw data with imaging system characteristics. A high-confidence MTF result at spatial frequencies near 200 cycles/mm is obtained. We present results at several visible light wavelengths with a 6.8-microm-pixel CCD. Pixel response functions are derived from the MTF results.

Enhanced quantum interference effects in parallel Josephson junction arrays

We have calculated the total critical current as a function of applied magnetic flux for a superconducting interferometer consisting of many Josephson junctions in parallel. An enhancement and narrowing of the periodic principal maxima in the critical current versus flux characteristic is predicted as the number of junctions in parallel increases, even when the effects of finite self- and mutual inductances and nonuniformity of the junction critical currents are included in the calculations. The possible application of the superconducting quantum interference grating, or SQUIG, for the detection of magnetic flux is discussed.

A theory of particle interference based upon the uncertainty principle

In the original paper (i) it was denostrated that the wave explanation traditionally employed within quantum mechanics to account for particle interference is apparently untenable because it disagrees with the special theory of relativity! A superior explanat ion based on Heisenberg's uncertainty principle and in agreement with special relativity was set forth which also gi~es the correct positions of the so-called , interference maxima and minima ,. (The adjective (~ so-called )) is used here because, in the context of this alternative explanation, the maxima and minima are not produced by the interference of waves, but rather are produced by the grating interfering with the particles.) A problem for understanding will, no doubt, be that the reader is accustomed to thinking of the uncertainty principle as having been derived from the de Broglie wavelength. In contrast to this my approach has been to assume the primacy of the uncerta in ty principle so that the de Broglie wave-length appears as a sort of a reflection of it. However, that they are not equivalent is apparent from the reconsideration of the particle interference problem given in the original paper. In this second paper we will explore some important additional consequence of this alternative approach. One immediate consequence is that we obviate a difficulty that has long been worrisome in quantum mechanics; viz., the problem of the collapse of the wave system. In the wave approach to the interference problem it has been noted that , if the electron hits a scintillation screen after passing through the interference grating, then the de Broglie wave should instant ly collapse to that small region of the scintillation screen struck by the electron. Since the de Broglie wave is very extensive, for some portion of the wave to traverse each slit of the grating, this essentially instantaneous collapse of the de Broglie wave constitutes another disagreement with the theory of special relativity.

Galactic ring nebulae associated with Wolf-Rayet stars. II - M1-67: A nebula braked by the interstellar medium

view Abstract Citations (40) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Galactic ring nebulae associated with Wolf-Rayet stars. II. M 1-67 : a nebula braked by the interstellar medium. Chu, Y. -H. ; Treffers, R. R. Abstract It is pointed out that the nebula M1-67 is characterized by two uncommon properties. First, if it is a planetary nebula, it is the only one known with a WN nucleus. Second, both the central star 209 BAC, often called Merrill's star, and the nebula are moving at a high heliocentric velocity, approximately plus 200 km/s. The considered investigation concerning M1-67, takes into account a photographic study conducted with a narrow band interference filter and the mapping of the radial velocity of the nebula with a Fabry-Perot interferometer. It is concluded that the nebula M1-67, like planetary nebula, is made of matter, which has been ejected from the central star. It is thought possible that the star had ejected material prior to the oldest component currently observed and that the earlier ejecta have dissipated and can no longer be detected. An illustration is given that nebular braking is possible. Publication: The Astrophysical Journal Pub Date: October 1981 DOI: 10.1086/159318 Bibcode: 1981ApJ...249..586C Keywords: Astronomical Spectroscopy; Galactic Structure; Interstellar Matter; Planetary Nebulae; Wolf-Rayet Stars; Fabry-Perot Interferometers; Galactic Nuclei; High Resolution; Interference Grating; Propagation Velocity; Radial Velocity; Stellar Mass Ejection; Astronomy full text sources ADS | data products SIMBAD (2) Related Materials (7) Part 1: 1981ApJ...249..195C Part 3: 1981ApJ...250..615C Part 4: 1982ApJ...254..562C Part 5: 1982ApJ...254..569T Part 6: 1982ApJ...254..578C Part 7: 1982ApJ...254..132T Part 8: 1983ApJS...53..937C

The holographic hallmarking of interference diffraction gratings

It has been demonstrated that by recording a hologram orthogonal to the grooves of an interference grating, it is possible to record information which will identify the grating without degrading its spectral performance.

Photoelectric filter photometry of planetary nebulae

view Abstract Citations (66) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric filter photometry of planetary nebulae. Kaler, J. B. Abstract Results are presented for photoelectric photometry of 25 planetary nebulae using 11 interference filters (eight for emission lines and three for the continuum). The instrument employed was a single-channel photometer with a cooled photomultiplier coupled to a 40-in. Cassegrain telescope operating at either f/7.6 or f/13.5. Absolute H-beta fluxes are determined for 22 nebulae, and fluxes relative to H-beta are derived for 23 nebulae in at least one of these lines: forbidden O III at 4959 A, forbidden Ar IV at 4740 A, He II at 4686 A, He I at 4471 A, forbidden Ne III at 3868 A, and forbidden O II at 3727 A. Apparent B and V magnitudes are obtained for most of the central stars. The ratios He(+)/H(+), He(2+)/H(+), and He/H are calculated for 10 nebulae; upper limits are set on these ratios for two others. Publication: The Astrophysical Journal Pub Date: November 1976 DOI: 10.1086/154808 Bibcode: 1976ApJ...210..113K Keywords: Astronomical Photometry; Electrophotometry; Optical Filters; Planetary Nebulae; Radiant Flux Density; Abundance; Forbidden Bands; H Beta Line; Helium; Hydrogen; Interference Grating; Line Spectra; Stellar Magnitude; Astrophysics full text sources ADS | data products SIMBAD (25)

Interference (holographic) diffraction gratings

Diffraction gratings in which the grooves are formed by recording optical interference fringes are rapidly becoming established as alternatives to ruled gratings. In many respects they compare favourably with ruled gratings, but because of both the limitations and the novel features of the interference method of manufacture, a straightforward comparison is not always possible. Whether a ruled or interference grating is to be preferred will strongly depend upon the use to which it is to be put.

Josephson junction interference grating

The maximum current through multiple Josephson structures as a function of applied magnetic field is presented. Particular emphasis is placed on the Josephson penetration depth effects and geometrical considerations. The symmetrical and asymmetrical current feed two-, three-, four-, and five-junction gratings are analyzed and discussed. The Josephson penetration depth is shown to control the amplitude of the interference and diffraction patterns of the interference grating. In addition the interior-junction-length/interference-loop-area product is shown to control the operating mode of the interference grating. The dependence of the magnetic field sensitivity and interference pattern amplitude on the number of junctions is discussed.

A superconducting interference grating

The research on the properties of weakly connected superconductors has been extended from two to more than two point contacts, carefully adjusted between two superconductors, in this way forming an interference grating. Special attention has been paid to the shape of the curves representing the voltage oscillations as a function of an applied magnetic field at constant applied current. The shape of these voltage oscillations appears to be in qualitative agreement with the calculated shape of the critical-current oscillations if one applies the basic Josephson relations to the multiple contact and neglects the self-inductances and mutual inductances of the holes between the contacts of the grating and if one further assumes that all contacts and holes are identical. The performance of the grating is discussed in comparison with a fluxconcentrator developed as a magnetometer in this laboratory.