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Showing papers on "Interference (wave propagation) published in 1988"


Book ChapterDOI
TL;DR: The phase modulation in an interferometer can be induced by moving a mirror, tilting a glass plate, moving a grating, rotating a half-wave plate or analyzer, using an acoustooptic or electro-optic modulator, or using a Zeeman laser as mentioned in this paper.
Abstract: Publisher Summary This chapter describes the phase-measurement interferometry techniques. For all techniques, a temporal phase modulation is introduced to perform the measurement. By measuring the interferogram intensity as the phase is shifted, the phase of the wavefront can be determined with the aid of electronics or a computer. Phase modulation in an interferometer can be induced by moving a mirror, tilting a glass plate, moving a grating, rotating a half-wave plate or analyzer, using an acousto-optic or electro-optic modulator, or using a Zeeman laser. Phase-measurement techniques using analytical means to determine phase all have some common denominators. There are different equations for calculating the phase of a wavefront from interference fringe intensity measurements. The precision of a phase-measuring interferometer system can be determined by taking two measurements, subtracting them, and looking at the root-meansquare of the difference wavefront. The chapter discusses the simulation results. The elimination of the errors that reduce the measurement accuracy depends on the type of measurement being performed. Phase-measurement interferometry (PMI) can be applied to any two-beam interferometer, including holographic interferometers. Applications can be divided into: surface figure, surface roughness, and metrology.

1,340 citations


Journal ArticleDOI
TL;DR: It is shown that it may be made to further enhance the sensitivity within a narrow bandwidth, becoming tuned recycling, and the various sensitivity-bandwidth combinations, together with the tuning properties, are discussed.
Abstract: Laser interferometers may detect gravitational waves by sensing the strain in space produced by their passage. The resultant change in intensity of an interference fringe must be observable against a background noise due to the statistical fluctuations in the number of detected photons. Optimization of the detector sensitivity thus involves devising an optical system which both maximizes the signal and minimizes the noise. This is attempted in the various arrangements known collectively as light recycling. Here, the performance of these systems is quantitatively assessed. Standard or broadband recycling functions essentially by making efficient use of the available light, but it is shown that it may also be made to further enhance the sensitivity within a narrow bandwidth, becoming tuned recycling. This works, as do all the narrow-band variants, by arranging for both the laser light and a gravitational-wave-induced sideband to be resonant in the optical system. The original narrow-band system, resonant recycling, can also be made broadband; the various sensitivity-bandwidth combinations, together with the tuning properties of such a system, are discussed.

358 citations



Journal ArticleDOI
TL;DR: In this article, the interference coefficients were determined for the 5-mm wavelength oxygen lines broadened by air and solved by the Twomey-Tikhonov method, which minimizes a cost function, subject to the condition of constant measurement error variance.
Abstract: Interference coefficients describe the non-Lorentzian effect that arises as pressure broadening causes lines to overlap. These coefficients, one for each line, are at moderate pressures related linearly to absorption and dispersion. They are determined here for the 5-mm wavelength oxygen lines broadened by air. The method includes four a priori constraints on off-diagonal elements of the relaxation matrix, which produce the interference effect: (1) detailed balance; (2) intra-branch submatrices are assumed to be identical; (3) coupling between the + and - branches is ignored; (4) coupling between the (positive-frequency) resonances and the nonresonant and negative-resonant branches is represented by a small bias term in the interference coefficients. The linear equations relating measured dispersion to the interference coefficients are solved by the Twomey-Tikhonov method, which minimizes a cost function, subject to the condition of constant measurement-error variance. The cost function is chosen to minimize the variation of elements along diagonals of the intra-branch relaxation submatrix. Implications for atmospheric radiative transfer are briefly discussed.

99 citations


Journal ArticleDOI
TL;DR: To measure small-angle rotations, the two mirrors of a Michelson interferometer are replaced by right-angle prisms and rotation of the latter shifts the interference pattern.
Abstract: To measure small-angle rotations, the two mirrors of a Michelson interferometer are replaced by right-angle prisms. Rotation of the latter shifts the interference pattern. Measurement of that shift gives, after calibration, the rotation. The experimental setup is insensitive to vibrations, provides good linearity between +5 degrees and -5 degrees , and has a resolution of 10(-4) deg.

79 citations


Journal ArticleDOI
TL;DR: It is found that the interference noise plays a dominant role in determining the operating margin of the DRAM and that a novel process or a cell array architecture for minimizing the interferencenovelity is indispensable in 16-MbDRAM and beyond.
Abstract: A kind of data-line (DL) interference noise in a scaled DRAM cell array is found and studied through analysis. The dynamic behavior of cell arrays due to sense-amplifier operation is derived analytically. Analysis shows that the amount of interference noise is more than three times larger than expected from simple data-line coupling. A novel experimental technique for precise noise determination is developed to verify the analysis. Analytical results are in good agreement with the experimental data. It is found that the interference noise plays a dominant role in determining the operating margin of the DRAM and that a novel process or a cell array architecture for minimizing the interference noise is indispensable in 16-Mb DRAM and beyond. >

73 citations


Journal ArticleDOI
Z. Y. Ou1
TL;DR: In this article, the quantum theory of fourth-order interference of light is presented in a general format and compared with classical wave theory, and conditions under which nonclassical phenomena occur are discussed.
Abstract: The quantum theory of fourth-order interference of light is presented in a general format and compared with classical wave theory. The conditions under which nonclassical phenomena occur are discussed. In particular, the interference between the quantum field and classical field may give rise to a nonclassical effect. For some special states of light, the interference pattern does not disappear even though one field is much stronger than the other, for which no classical analog exists. Fourth-order effects in the interference between two independent fields are analyzed in detail. It is pointed out that the fourth-order interference between independent fields will not disappear when the integration time of detection is of the order of the reciprocal bandwidth of the two light fields as long as the spectra of the two fields are symmetric around the same center frequency, and for some correlated fields, the interference does not vanish even if the detection time is much larger than the reciprocal bandwidth of the fields. A new type of fourth-order interference experiment involving a beam splitter is proposed in which local realism of the Einstein-Podolsky-Rosen form is violated for quantum mechanics. This general argument is then applied to the interference between two photons generated in the parametric down-conversion process. The possibility of violations of Bell's inequalities in interference experiments is investigated.

63 citations


Journal ArticleDOI
TL;DR: The real-time direct interference-term measurement for a two-wave-mixing experiment in photorefractive crystals comprises phase modulation of one of the interfering beams and synchronous detection of the first and second harmonics in the resulting output irradiance modulation.
Abstract: We report the real-time direct interference-term measurement for a two-wave-mixing experiment in photorefractive crystals. Knowledge of the interference term may provide information concerning diffraction efficiency, interference pattern-to-recorded hologram phase shift, and optical activity and anisotropic diffraction properties of these materials. This method comprises phase modulation of one of the interfering beams and synchronous detection of the first and second harmonics in the resulting output irradiance modulation. Simultaneous detection of both harmonics enables the measurement to be made even in strongly perturbed conditions, since one harmonic is used for measuring and the other is used for operating an active stabilization system. Experimental results for Bi12TiO20 are reported.

55 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that energy transfer arises from the contribution of the π/2 component of the index modulation generated by interference generated by the interference of (Ip,I−1) caused by the large thermal index change that arises when the cell operates near the phase transition temperature.
Abstract: Signal‐beam amplification is achieved in degenerate two‐wave mixing experiments in liquid crystals at the wavelength λ=106 μm of the cw CO2 laser The origin of the dynamic grating is the large thermal index change that arises when the cell operates near the phase transition temperature Maxwell’s equations are analytically solved for the calculation of the amplitude variations of the incident waves (Ip: pump, Is: signal) and of the self‐diffracted wave (I−1) It is shown that energy transfer arises from the contribution of the π/2 component of the index modulation generated by the interference of (Ip,I−1) The resulting three‐wave model yields good agreement with the experimental results

53 citations


Journal ArticleDOI
TL;DR: In this paper, the authors report the results of neutron interferometric experiments, extending the range and precision of the COW gravitationally-induced quantum interference experiment of Staudenmann and co-workers.
Abstract: We report the results of neutron interferometric experiments, extending the range and precision of the COW gravitationally-induced quantum interference experiment of Staudenmann and co-workers. These experiments provide a test of the principle of equivalence in the quantum limit. High precision data (1 part in 1000) is presented. The frequency of the quantum interference oscillations, and the loss of contrast observed as a function of increasing gravitational potential energy difference are compared with the recent interferometer dynamical diffraction calculations of Bonse and Wroblewski and of Horne. Theory and experiment are found to differ by 0.8%.

53 citations


Patent
30 Mar 1988
TL;DR: In this article, an apparatus for measuring changes in a variable interference section of an interferometer comprises a laser source for producing beams of the frequency n 1 and the frequency N 2, polarizing beam splitters for producing cross-polarized partial beams of frequency N 1 or n 2, modulators for displacing the frequency of one of the partial beams by frequency f 1 or f 2, a pair of deflecting mirrors in each case and polarizing beams splitters are used to combine the partial beam n 1, n 1 +f 1, n 2, n
Abstract: An apparatus for measuring changes in a variable interference section of an interferometer comprises a laser source for producing beams of the frequency n 1 and the frequency n 2 , polarizing beam splitters for producing cross-polarized partial beams of frequency n 1 or n 2 , modulators for displacing the frequency of one of the partial beams by frequency f 1 or f 2 , a pair of deflecting mirrors in each case and polarizing beam splitters for combining the partial beam n 1 , n 1 +f 1 , n 2 , n 2 +f 2 . The apparatus further includes two photodetectors, upstream of which are arranged a polarizer, a Michelson interferometer, a non-polarizing beam splitter for splitting the partial beams in each case into a measuring light beam or a reference light beam. The reference light beam passes to an associated photodetector. The measuring light beam passes into the Michelson interferometer and then to the associated photodetector. The signals of the photodetectors are demodulated according to the amplitude and the phase difference between the two demodulated signals is determined. This phase difference is only dependent on the position of a measurement object and the equivalent wavelength of the difference n 1 -n 2 . A method for measuring changes by determining positions or distances is performed by the apparatus.

Journal ArticleDOI
TL;DR: A digital phase measuring interferometer with a frequency-modulated laser diode using the integratedbucket technique is described; the rms repeatability obtained was lambda/80 and some experimental results with the interferometers are presented.
Abstract: A digital phase measuring interferometer with a frequency-modulated laser diode using the integrated-bucket technique is described. The injection current is continuously changed to introduce a time-varying phase difference between the two beams of an unbalanced Twyman-Green interferometer. The intensity of the interference patterns is integrated with a CCD array sensor for intervals of one-quarter period of the fringe. Using the intensity data a microcomputer calculates the phase to be detected. Some experimental results with the interferometer are presented; the rms repeatability obtained was λ/80.

Patent
03 Aug 1988
TL;DR: In this paper, a broad bandwidth laser pulse is spectrally dispersed spatially so that the frequency components thereof are spread apart, and a disperser (grating) provides an output beam which varies spatially in wavelength in at least one direction transverse to the direction of propagation of the beam.
Abstract: In order to control the intensity of a laser beam so that its intensity varies uniformly and provides uniform illumination of a target, such as a laser fusion target, a broad bandwidth laser pulse is spectrally dispersed spatially so that the frequency components thereof are spread apart. A disperser (grating) provides an output beam which varies spatially in wavelength in at least one direction transverse to the direction of propagation of the beam. Temporal spread (time delay) across the beam is corrected by using a phase delay device (a time delay compensation echelon). The dispersed beam may be amplified with laser amplifiers and frequency converted (doubled, tripled or quadrupled in frequency) with nonlinear optical elements (birefringent crystals). The spectral variation across the beam is compensated by varying the angle of incidence on one of the crystals with respect to the crystal optical axis utilizing a lens which diverges the beam. Another lens after the frequency converter may be used to recollimate the beam. The frequency converted beam is recombined so that portions of different frequency interfere and, unlike interference between waves of the same wavelength, there results an intensity pattern with rapid temoral oscillations which average out rapidly in time thereby producing uniform illumination on target. A distributed phase plate (also known as a random phase mask), through which the spectrally dispersed beam is passed and then focused on a target, is used to provide the interference pattern which becomes nearly modulation free and uniform in intensity in the direction of the spectral variation.

Proceedings ArticleDOI
15 Jun 1988
TL;DR: A novel IZCR algorithm is proposed that maximizes the number of channels that satisfy a required carrier-to-interference ratio (CIR) and can be reduced by equal to or more than 10 dB by adopting both ATPC and new IZ CR.
Abstract: In cellular radio systems, cochannel interference determines frequency reuse distance. To achieve high-capacity systems, cochannel interference reduction is considered a key item. Intrazone channel reassignment (IZCR) and adaptive transmitter power control (ATPC), are effective techniques to reduce cochannel interference. A novel IZCR algorithm is proposed that maximizes the number of channels that satisfy a required carrier-to-interference ratio (CIR). By computer simulations, the interference reduction effects by either IZCR or ATPC and by both ATPC and IZCR are clarified. With the call block rate of 0.03 and the outage probability of 0.01, the CIR margin can be reduced by equal to or more than 10 dB by adopting both ATPC and new IZCR. >

Journal ArticleDOI
TL;DR: It is demonstrated that the new quantum interference effect between the split paths of a coherent particle beam which is in a uniformly rotating frame should be observable even in a frame which is rotating no faster than the second hand on a clock.
Abstract: We discuss a new quantum interference effect between the split paths of a coherent particle beam which is in a uniformly rotating frame. The effect is the mechanical counterpart of the Aharonov-Bohm effect usually associated with interference in magnetic fields. We demonstrate that the effect should be observable even in a frame which is rotating no faster than the second hand on a clock.

Patent
27 Sep 1988
TL;DR: In this paper, a plane wave of electromagnetic energy of predetermined dimensions is directed toward the object at a predetermined angle of incidence, and the characteristics of the interference pattern permit the dimension of the object to be deduced.
Abstract: A dimension of an object disposed on a substrate, such as the width of a line of material deposited on a substrate in an integrated circuit manufacturing procedure, is measured by directing a plane wave of electromagnetic energy of predetermined dimensions toward the object at a predetermined angle of incidence. Electromagnetic energy scattered from two predetermined parts or features, such as the edges, of the object are combined so that they produce an interference pattern in space varying between maxima and minima. The characteristics of the interference pattern permit the dimension of the object to be deduced.

Patent
21 Jun 1988
TL;DR: In this paper, a pencil-beam interferometer with an inherent large depth-of-field (DOF) was used for noncontact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation mirrors.
Abstract: The design of a long-trace surface profiler for the non-contact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation (SR) mirrors. The optical system is based upon the concept of a pencil-beam interferometer with an inherent large depth-of-field. The key feature of the optical system is the zero-path-difference beam splitter, which separates the laser beam into two colinear, variable-separation probe beams. A linear array detector is used to record the interference fringe in the image, and analysis of the fringe location as a function of scan position allows one to reconstruct the surface profile. The optical head is mounted on an air bearing slide with the capability to measure long aspheric optics, typical of those encountered in SR applications. A novel feature of the optical system is the use of a transverse "outrigger" beam which provides information on the relative alignment of the scan axis to the cylinder optic symmetry axis.

Journal ArticleDOI
TL;DR: It is shown experimentally that propagation of light waves in an effectively rotating fiber-optic ring resonator leads to a photon band structure due to interference of elastically scattered waves.
Abstract: We show experimentally that propagation of light waves in an effectively rotating fiber-optic ring resonator leads to a photon band structure due to interference of elastically scattered waves. The rotation is simulated by means of a Faraday-active element in the ring.

Journal ArticleDOI
C. Desem1
TL;DR: In this paper, it was shown that mixing of the optical fields in the photodetector leads to interference which may impose a limitation on the system bandwidth or the number or available channels.
Abstract: It is shown that when multiple optical carriers are used in a subcarrier multiplexing system, the mixing of the optical fields in the photodetector leads to interference which may impose a limitation on the system bandwidth or the number or available channels.

Journal ArticleDOI
TL;DR: Both laboratory and field tests show that adaptive interference-suppression systems can be designed and built for real-life environments expected in broadcast and relay stations.
Abstract: Receiving antennas and receivers can be collocated with the transmitting antennas and transmitters, if appropriate interference suppression is effected. Since the time-varying characteristics of the interference from adjacent transmitters may not be known a priori, and since the propagation path characteristics may change with time, interference needs to be suppressed by adaptive means. Operational characteristics of the adaptive control system in a shortwave broadcast station and expected degree of cancellation of the unwanted interference are discussed. Some recent tests to evaluate the effectiveness of the adaptive control in the relay station of Voice of America at Delano, California are outlined. Both laboratory and field tests show that adaptive interference-suppression systems can be designed and built for real-life environments expected in broadcast and relay stations. >

Journal ArticleDOI
TL;DR: The performance of direct-sequence spread-spectrum systems using a suppression filter in the presence of multiple narrow band interference with rational spectral densities is analyzed.
Abstract: The performance of direct-sequence spread-spectrum systems using a suppression filter in the presence of multiple narrow band interference with rational spectral densities is analyzed. Both BPSK and QPSK systems are considered, and analytical expressions for both the means-square error of the filter output and the performance improvement are established. When the bandwidths of the narrow band components of the interference are all small, approximate expressions are obtained and used to provide further insight into the behavior of the system. Results are presented for the limiting case when the bandwidths approach aero (i.e. when multiple narrow band interference becomes multiple sinusoidal interference). >

Proceedings ArticleDOI
23 Oct 1988
TL;DR: It is concluded that large improvements can be achieved for a wider range of interference modulations than can be handled by any previously realized technique known to the author.
Abstract: A signal processing technique designed to suppress interference in direct sequence spread spectrum receiving systems is described. The basic idea is to optimize the detection process dynamically in the presence of current interference. This is accomplished by estimating the statistics of the interference and then using this information to derive a nonlinear transform to apply to the signal-plus-noise. As the statistics of the interference change, the measured distributions and the resulting transformations do so also. This adaptation is open-loop, thus avoiding convergence problems. It is concluded that large improvements (tens of dB) can be achieved for a wider range of interference modulations than can be handled by any previously realized technique known to the author. >

Journal ArticleDOI
15 Oct 1988-EPL
TL;DR: In this article, a novel quantum interference effect in ballistic transport is described: the interference of coherently excited magnetic edge states in a two-dimensional electron gas, which explains the characteristic features of the unexpected fine structure observed recently in an electron focusing experiment.
Abstract: A novel quantum interference effect in ballistic transport is described: the interference of coherently excited magnetic edge states in a two-dimensional electron gas. The effect explains the characteristic features of the unexpected fine structure observed recently in an electron focusing experiment.

Journal ArticleDOI
TL;DR: The interference pattern from a light source containing a single excited atom was observed with an interferometer 45 m in length as mentioned in this paper, where the visibility of the single-photon interference pattern was the same as that obtained with a high-intensity light source to within the experimental uncertainty of \ifmmode\pm\else\textpm\fi{}5%.
Abstract: The interference pattern from a light source containing a single excited atom was observed with an interferometer 45 m in length. The visibility of the single-photon interference pattern was the same as that obtained with a high-intensity light source to within the experimental uncertainty of \ifmmode\pm\else\textpm\fi{}5%.

Journal ArticleDOI
TL;DR: In this paper, a monolithically designed four plate perfect crystal interferometer was tested and compared to calculated interference patterns based on plane wave theory, and several features of multi-plate interferometry and a modified phase echo system were discussed.
Abstract: A monolithically designed four plate perfect crystal interferometer was tested. The experimental results were compared to calculated interference patterns based on plane wave theory. Inside the four plate system are three independent interferometer loops which permit the definition of three effective phase shifts and determine the intensity modulation behind the interferometer crystal. Absorbing phase shifters cause a partial beam path detection and, therefore, influence the interference pattern by their individual location. Several features of multiplate interferometry and a modified phase echo system are discussed.

Journal ArticleDOI
TL;DR: Using the nonlinear oscillator model as a prototype medium exhibiting intrinsic optical bistability, the inhomogeneous absorption of the electromagnetic field is investigated and it is found that the plane-wave results for the center of the beam remain reliable down to Fresnel numbers of order unity and in media that are smaller than the linear absorption length.
Abstract: Using the nonlinear oscillator model as a prototype medium exhibiting intrinsic optical bistability, we investigate the inhomogeneous absorption of the electromagnetic field. The forward- and backward-field amplitudes and diffraction effects are retained in the mathematical description. Analytic results are given in the limit of plane-wave propagation under steady-state conditions. The transmitted and reflected intensity exhibit a structure that is determined by the spatial inhomogeneity of the absorption in the longitudinal direction. The transmitted intensity has a structure that is dependent on the length of the medium. The reflected intensity has an interference structure from light reflected at the front surface and the internal boundary separating a high-polarization from a low-polarization branch. A degenerate-four-wave-mixing experiment is predicted to be a very sensitive probe of the internal boundary and the interference between the forward and backward field. The phase-conjugate signal develops large oscillations as the input field is varied. Numerical results for diffraction effects are also given, and we find that the plane-wave results for the center of the beam remain reliable down to Fresnel numbers of order unity and in media that are smaller than the linear absorption length.

Proceedings ArticleDOI
11 Apr 1988
TL;DR: A method of adding constraints so as to reduce the total number of degrees of freedom available to the processor is introduced to provide reduced computational load while preserving the interference rejection capabilities of the array.
Abstract: Linearly-constrained adaptive arrays have wide application for interference rejection. The authors introduce a method of adding constraints so as to reduce the total number of degrees of freedom available to the processor. For the case of arrays containing a large number of elements, this is a particularly useful approach to providing reduced computational load while preserving the interference rejection capabilities of the array. These additional constraints are chosen to efficiently constrain the adaptive weight vector solution space. The resulting reduced complexity adaptive array is shown to have remarkably good sidelobe control over a wide range of interference conditions. >

Journal ArticleDOI
TL;DR: In this paper, the authors measured the dispersion of single-mode fibers by a spectral scanning of the interference signal in a Michelson interferometer and obtained the propagative refractive index directly from the phase-difference variations with the wavelength between a light beam propagated through the fiber and a reference beam.
Abstract: Chromatic dispersion characteristics around zero-dispersion wavelength have been measured in short samples of single-mode fibers by a spectral scanning of the interference signal in a Michelson interferometer. The propagative refractive index is directly obtained from the phase-difference variations with the wavelength between a light beam propagated through the fiber and a reference beam. The optimum operative conditions of the interferometer for obtaining the unequivocal analysis of experimental signals are discussed. The accuracy of the results obtained shows the reliability of the method for a complete dispersion characterization. >

Journal ArticleDOI
TL;DR: A simplified version of the Lee-Smith algorithm is proposed for computing the probability of outage and the bit error rate (BER) due to autointerference in multiple-access spread-spectrum radio systems.
Abstract: A simplified version of the Lee-Smith algorithm (W.C. Y. Lee and H.L. Smith, ibid., vol. VT-32, p.177-90, May 1983) is proposed for computing the probability of outage and the bit error rate (BER) due to autointerference in multiple-access spread-spectrum radio systems. The model assumes a pair of transmitting and receiving radios in a region where there are other radios operating in the same band. Each radio is characterized by its own spatial distribution, transmitting power, activity coefficient (denoting the percentage of time the radio is active), antenna height, and a set of carrier frequencies. The probability of outage with respect to the log-normal field-strength attenuation is derived assuming that the probability of having more than one interferer is very low. To allow maximal flexibility, the spatial, carrier frequency, and activity distributions are computer simulated for each radio. As an example of applying the method, the probability of error of an asynchronous frequency-hopping (FH) and a hybrid frequency-hopping/direct sequence (FH/DS) modulation schemes in environments with thousands of radios is reported. >

Patent
08 Apr 1988
TL;DR: In this paper, the envelope of the burst-like modulated wave can be changed gradually at the carrier on/off timing in order to reduce the interference of the modulated waves with the adjacent channels without degrading the transmission efficiency.
Abstract: A modulator for generating a burst-like modulated wave used in a multi-carrier transmission type communication system in which a plurality of modulated waves including at least one burst-like modulated wave exist on the same transmission line and the frequency band occupied by energy of each of the plurality of modulated waves is limited. Polarities of the transmission code which appear before and after either of on-timing and off-timing of the carrier on/off switched to obtain the burst-like modulated wave among the plurality of modulated waves are inverted to each other, whereby the envelope of the burst-like modulated wve can be changed gradually at the carrier on/off timing in order to reduce the interference of the modulated wave with the adjacent channels without degrading the transmission efficiency.