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The s-wave time-independent Schrodinger equation with an isotropic velocity-dependent potential is considered. We have used perturbation theory to calculate the scattering phase shifts when the energy is changed by a small amount ΔE from an arbitrary unperturbed value [E.sub.0]. The validity of our results was tested by comparing the perturbed phase shifts to those obtained exactly by solving the Schrodinger equation. We assumed the local potential to have the form of a finite square well and the velocity-dependent part of the potential to have the form of a Yukawa potential. Key words: scattering phase shifts, velocity-dependent potential, finite square well, Yukawa potential. Nous analysons la solution en onde s de l'equation de Schrodinger independante du temps avec un potentiel dependant de la vitesse. Nous utilisons la theorie des perturbations pour calculer les dephasages de diffusion lorsque l'energie est variee par une petite quantite ΔE d'une valeur arbitraire non perturbee [E.sub.0]. Nos resultats sont verifies en les comparant avec ceux obtenus de la solution exacte de l'equation de Schrodinger. Nous posons que le potentiel local est un potentiel carre fini et que celui dependant du temps a la forme d'un potentiel de Yukawa. [Traduit par la Redaction] Mots-cles: dephasages de diffusion, potentiel dependant du temps, potentiel carre fini, potentiel de Yukawa. PACS Nos.: 03.65.Nk, -31.15.Md., 1. Introduction The energy dependence of the scattering phase shifts as we move away from the zero energy limit has been of interest in many old and recent works. In [...]

In temporal phase-shifting-based digital holographic microscopy, high-resolution phase contrast imaging requires optimized conditions for hologram recording and phase retrieval. To optimize the phase resolution, for the example of a variable three-step algorithm, a theoretical analysis on statistical errors, digitalization errors, uncorrelated errors, and errors due to a misaligned temporal phase shift is carried out. In a second step the theoretically predicted results are compared to the measured phase noise obtained from comparative experimental investigations with several coherent and partially coherent light sources. Finally, the applicability for noise reduction is demonstrated by quantitative phase contrast imaging of pancreas tumor cells. OCIS codes: 090.0090, 090.1995, 100.5070, 180.0180.

Previous implementations of the iterative phase shifting method, in which the phase of a test object is computed from measurements using a phase shifting interferometer with unknown positions of the reference, do not provide an accurate way of knowing when convergence has been attained. We present a new approach to this method that allows us to deterministically identify convergence. The method is tested with a home-built Fizeau interferometer that measures optical surfaces polished to [lambda]/100 using the Hydra tool. The intrinsic quality of the measurements is better than 0.5 nm. Other possible applications for this technique include fringe projection or any problem where phase shifting is involved. OCIS codes: 120.0120, 120.3180, 120.5050.

The application of terahertz time-domain spectroscopy (THz-TDS) and imaging to differentiate flat and curved surfaces in reflection via the THz Gouy phase shift is demonstrated. For a THz-TDS system that is aligned for reflection from a flat surface, the presence of a curved surface displaces the image focal plane from the detector plane, resulting in a Gouy phase shift. The potential of utilizing this configuration for estimating the number and size of curved objects is discussed with particular emphasis on agriculture crop yield estimates. OCIS codes: 110.6795, 120.0280, 280.1415.

An alternative method for digital holography using a quadrature phase-shifting interferometer for high-speed measurement is presented. We show that it has image quality equal to the four-bucket method. In addition, it requires fewer imaging devices. Two quadrature phase-shifting fringe patterns are acquired in each state of an object changed temporally. The phase calculation method with these four fringe patterns gives the phase distribution of the hologram. This digital phase hologram is reconstructed to yield an object image by the Fresnel transform using digital convolutions with the fast Fourier transform algorithm. Verification results of simulations and experiments are given. OCIS codes: 090.1995, 120.3180, 120.5050, 100.3020.

We present a common-path phase-shitting interferometer in which photonic crystal polarizers (PCPs) are utilized as a reference mirror and a phase shifter, allowing ultracompact and highly sensitive optics. When a laser beam polarized at 45[degrees] relative to the optical axis of the PCP-based reference mirror is incident, the polarization component parallel to the optical axis (s-polarized beam) is reflected and used as a reference beam. The perpendicular component (p-polarized beam) passes through the PCP coupled with a quarter-wave plate (QWP) and serves as a probe beam. This beam, with its polarization transformed in the sequence p, right-circular, s, left-circular, and p, irradiates the sample surface twice, doubling the phase change due to displacement of the sample. The probe beam is then retransmitted through the PCP, where it recombines with the reference beam. Four interferogram channels in phase quadrature are generated using a newly developed phase shifter, composed of a QWP and a monolithically integrated array of four PCPs. Preliminary experiments demonstrate that the PCPs perform successfully as a reference mirror and a phase shitter, and that the interferometer has a remarkable displacement sensitivity, as low as 40 pm. OCIS codes: 050.5298, 050.6624, 100.5088, 120.3180, 120.5050, 260.5430.

We describe an apparatus for generating rotating sound waves in free space by superimposing two orthogonal standing modes with a quarter wave phase lag. The creation of a standing wave from the superposition of two counter-rotating waves is also possible with the same apparatus. The experiment permits direct measurement of both the amplitude and phase structure of the sound waves. A demonstration of angular momentum transfer from rotating acoustic waves to matter in free field is also described.

Iterative least square phase-measuring techniques address the phase-shifting interferometry issue of sensitivity to vibrations and scanner nonlinearity. In these techniques the wavefront phase and phase steps are determined simultaneously from a single set of phase-shifted fringe frames where the phase shift does not need to have a nominal value or be a priori precisely known. This method is commonly used in laser interferometers in which the contrast of fringes is constant between frames and across the field. We present step-by-step modifications to the basic iterative least square method. These modifications allow for vibration insensitive measurements in an interferometric system in which fringe contrast varies across a single frame, as well as from frame to frame, due to the limited bandwidth light source and the nonzero numerical aperture of the objective. We demonstrate the efficiency of the new algorithm with experimental data, and we analyze theoretically the degree of contrast variation that this new algorithm can tolerate. OCIS codes: 120.3180, 120.5050, 120.7280, 180.3170.

We propose three amplitude filters for visualization of phase objects. They interact with the spectra of pure-phase objects in the frequency plane and are based on tangent and error functions as well as antisymmetric combination of square roots. The error function is a normalized form of the Gaussian function. The antisymmetric square-root filter is composed of two square-root filters to widen its spatial frequency spectral range. Their advantage over other known amplitude frequency-domain filters, such as linear or square-root graded ones, is that they allow high-contrast visualization of objects with large variations of phase gradients. OCIS codes: 070.0070, 070.1170, 070.6110, 120.0120, 120.5050.

Comparative research on fine spectrum analysis techniques (static and dynamic) has been carried out. The advantages of the dynamic method for fine spectrum study of heterolaser radiation as a method of study of the spectrum change under ultrasonic strain have been shown. An approach to fine dynamic spectrum analysis has been developed, and the treatment of experimental data on the spectrum dynamics of the InGaAsP/InP structures in the presence of surface acoustic waves has been carried out. Thus an appreciable contribution of the acousto-optic interaction (comparable with the acousto-electronic interaction), resulting in time modulation of resonance frequencies of the heterolaser optical resonator, was found. The second, no less important, result of the investigation consists of the finding of the possibility to determine phase shifts between acousto-optic and the acousto-electronic interactions. OCIS codes: 070.1060, 260.3060, 300.6260, 300.6380.

A noncontact, fast, accurate, low-cost, broad-range, full-field, easy-to-implement three-dimensional (3D) shape measurement technique is presented. The technique is based on a generalized fringe projection profilometry setup that allows each system component to be arbitrarily positioned. It employs random phase-shitting, multifrequency projection fringes, ultrafast direct phase unwrapping, and inverse self-calibration schemes to perform 3D shape determination with enhanced accuracy in a fast manner. The relative measurement accuracy can reach 1/10,000 or higher, and the acquisition speed is faster than two 3D views per second. The validity and practicability of the proposed technique have been verified by experiments. Because of its superior capability, the proposed 3D shape measurement technique is suitable for numerous applications in a variety of fields. OCIS codes: 110.6880, 120.2830, 120.6660, 150.6910.

We propose a novel approach to designing an optical filter with a flat-top and ultranarrow transmission band by using a sampled fiber Bragg grating (SFBG) having multiple equivalent phase shifts (EPSs). In the proposed approach, multiple EPSs are fabricated by adjusting several sampling periods of the SFBG. The obtained multiple EPSs are then arranged properly to get a flat-top transmission band in the narrow--1st reflection band of the SFBG, leading to the generation of a flat and ultranarrow transmission band. Filters with two or five EPSs are designed by simulation and experiment, with low ripples and ultranarrow l dB bandwidths observed in transmission bands. OCIS codes: 050.2770, 120.2440, 060.2340, 050.5080.

Diffractive optical devices using low-molar-mass liquid crystals are of great important for realizing numerical optical functions such as optical memory and information systems. In the present study the liquid crystalline gratings have been fabricated using a pair of photo-alignment substrates, and effects of the phase shift between the two photo-alignment substrates on the diffraction properties have been investigated. The liquid crystalline grating has been constructed with variable polarization dependence that can be controlled by the phase shift between the two photo-alignment substrates and twisted angles of the nematic directors. The theoretical considerations were also performed using the elastic continuum theory, Jones calculus, and diffraction theory. A guiding principle that controls the diffraction properties of the liquid crystalline grating cell was successfully presented. OCIS codes: 160.3710, 160.2900.

We propose a quantitative approach toward the detection of collimation of a coherent optical beam. For detection of collimation position of the collimator, a temporal phase shifting technique has been incorporated into Talbot interferometry. The slope of the phase maps depicts the collimation position of the collimator. This technique offers high precision, accuracy, and provides automated output. OCIS codes: 070.6760, 070.0070, 050.5080, 120.1680.

A sequence of electronic phase shifters and partial reflectors/transmitters is shown to form a true periodic scattering structure for electronic signals, complete with stop bands, interference, and dispersion effects, An experimental demonstration at 1 kHz is made with supporting theoretical results. As with conventional periodic media, sharp defect modes in the forbidden band arise when the periodicity is broken. When gain is added to the structure, a type of lasing action is observed that in almost every aspect is similar to conventional lasers.

We present a noncontact optical metrology measuring the pistons and tip/tilt angles of the 61 hexagonal segments of a compact-sized segmented mirror. The instrument has been developed within the scope of a design study for the European Extremely Large Telescope (E-ELT). It is used as reference sensor for cophasing of the mirror segments in closed-loop control. The mirror shape is also measured by different types of stellar light-based phasing cameras whose performances will be evaluated with regard to a future E-ELT. Following a description of the system architecture, the second part of the paper presents experimental results demonstrating the achieved precision: 0.48 nm rms in piston and 74 nrad rms in tip/tilt. OCIS codes: 120.3180, 120.3930, 120.3940, 120.5050.

An advanced spatial carrier phase-shifting (SCPS) algorithm based on least-squares iteration is proposed to extract the phase distribution from a single spatial carrier interferogram. The proposed algorithm divides the spatial carrier interferogram into four phase-shifted interferograms. By compensating for the effects of the variations of phase shifts between pixels and the variations of background and contrast, the proposed algorithm determines the local phase shifts and phase distribution simultaneously and accurately. Numerical simulations show that the accuracy of the proposed algorithm is obviously improved by compensating for the effects of background and contrast variations. The peak to valley of the residual phase error remains less than 0.002 rad when the magnitude of spatial carrier is in the range from [pi]/5 to [pi]/2 and the direction of the spatial carrier is in the range from 25[degrees] to 65[degrees]. Numerical simulations and experiments demonstrate that the proposed algorithm exhibits higher precision than the existing SCPS algorithms. The proposed algorithm is sensitive to random noise, but the error can be reduced by [square root of N] times if N measurements are taken and averaged. OCIS codes: 120.3180, 120.5050, 120.2650, 050.5080.

We present a new type of quadrature phase-shifting interferometer, which utilizes wave plates, a diffraction grating, and two lasers with different wavelengths, in order to acquire two sets of two quadrature fringe patterns in each wavelength formed on a single image sensor. This method for calculating with four phase-shifted fringe patterns gives us the phase sum and difference distributions between the phases in two wavelengths. This is also substantiated by results of our experiments. OCIS codes: 120.3180, 120.5050, 120.2650, 120.4820, 120.6660, 050.1950.

Phase-shifting interferometry with a genetic algorithm is proposed. The correction of unknown phase-shifting error is an important task in general phase-shifting interferometry. Since phase-shifting errors generate twin image noise in a reconstructed image, we can reduce the phase-shifting errors indirectly by trying to eliminate the twin-image noise in the reconstructed image. By Zernike polynomial expansion, the reconstructed image is represented as the evenness and oddness, where the ratio of the evenness and oddness is a measure of the amount of the twin image noise. We employ the genetic algorithm for finding the fittest phase shifts of interferograms by reducing the evenness of the reconstructed image, which leads to reduction of phase-shifting errors. This phase-shifting interferometry with a genetic algorithm is confirmed experimentally. OCIS codes: 070.2580, 090.1760, 230.6120.

We describe the historical and mathematical development of the polarization ellipse and the Poincare sphere. We point out the limitations of the Poincare sphere in its present use. To overcome these limitations we describe a new polarization sphere that we call the hybrid polarization sphere. This name is used because phase shifting and rotation of polarization components are described by small circles. Furthermore, longitudinal and latitudinal great circles are introduced so that the coordinates of a point on the sphere can be read. The hybrid polarization sphere is described and applied to polarizers, wave plates, and rotators. As a result, the hybrid polarization sphere can be used for both visualization and calculation and enables the difficulties associated with the Poincare sphere to be overcome. OCIS codes: 120.5410, 260.0260, 260.5430.

We present a new type of phase-shifting interferometer, which utilizes a polarizing prism to form quadrature phase-shifted fringe patterns onto a single imaging sensor. By changing the direction of linear polarization of the incident light orthogonally, four phase-shined fringe patterns in quadrature are obtained by taking images twice; thus it is possible to reduce phase errors caused by mechanical vibrations and air turbulence that occur in temporal phase-shifting interferometers. We present the principle of this interferometer with its theoretical analysis, using the Jones matrix, along with experimental results. OCIS codes: 120.3180, 120.5050, 120.2650, 120.4820, 120.6660.

We propose a parallel two-step phase-shifting digital holography technique capable of instantaneous measurement of three-dimensional objects, with a view toward measurement of dynamically moving objects. The technique is based on phase-shifting interferometry. The proposed technique carries out the two-step phase-shifting method at one time and can be optically implemented by using a phase-shifting array device located in the reference beam. The array device has a periodic two-step phase distribution, and its configuration is simplified compared with that required for three-step and four-step parallel phase-shifting digital holographies. Therefore the optical system of the proposed technique is more suitable for the realization of a parallel phase-shifting digital holography system. We conduct both a numerical simulation and a preliminary experiment in the proposed technique. The results of the simulation and the experiment agree well with those of sequential phase-shifting digital holography, and results are superior to those obtained by conventional digital holography using the Fresnel transform alone. Thus the effectiveness of the proposed technique is verified. OCIS codes: 090.0090, 090.1995, 090.1760, 090.2880, 100.3010.

We have compared the respective efficiencies of off-axis and phase-shifting holography in terms of noise and aliases removal. The comparison is made by analyzing holograms of a USAF target backlit with laser illumination, recorded with a charge-coupled device camera. We show that it is essential to remove the local oscillator beam noise, especially at low illumination levels. OCIS codes: 090.0090, 120.5060.

We describe an improved implementation of our previously reported common-path, phase shifting, and shearing interferometer. Using a time-multiplexed phase shifting scheme, we demonstrate higher sampling resolution, better light sensitivity, and use of arbitrary phase shifting algorithms. We describe microscopic imaging of the surface profile of a copper-plated silicon wafer and demonstrate that the system is vibration insensitive with ~[lambda]/100 repeatability. In a more general discussion of our method, we describe the different functional elements and suggest alternative designs and improvements. Possible uses include full-field coherent imaging and high dynamic range wavefront sensing, which we briefly discuss. OCIS codes: 100.3175, 120.0120, 180.3170, 350.5030.

A novel technique is proposed for measurement of the group delay (GD) and the differential group delay (DGD) of optical material, components, and fiber. This new method is based on continuous polarization modulation of the stimulus optical field as opposed to sequential polarization state switching used in the traditional phase shift method. A new complete derivation of the phase shift method, based on the modified Jones calculus of elementary matrices, is presented. The derivation reveals that the phase shift measurement actually depends on all eight elementary parameters that represent DGD and optical frequency derivatives of polarization-dependent loss (PDL). Thus, the new expression for the phase shift includes the combined effect of PDL and DGD. The proposed method is evaluated by measuring a section of polarization-maintaining fiber and a 50 km length of single-mode fiber over a wavelength range from 1530 to 1610 nm. Measurements of DGD in a long single-mode fiber are shown to be highly insensitive to environmentally induced GD drift. OCIS codes: 060.2330, 060.2300, 060.2340, 260.5430, 260.2030, 060.4080.

What we believe to be a new technique for the measurement of two-dimensional retardation distributions of a wave plate (WP) is presented. Phase-shifting interferometry has been applied for determining the relative retardation distribution using a Nomarski prism (NP) as a phase shitter. Absolute retardation distribution is obtained by accurately determining the position of zero retardation in the interference field using white light interference fringes and adjusting the phase distribution with respect to the zero retardation position. The measured absolute retardation distribution of the NP is subtracted from that obtained for the combination of the WP and NP, to get the desired retardation distributions for the WP. The technique is suitable for the measurement of phase retardation of both single and multiple order WPs, as the actual phase retardation distributions are obtained. Results obtained for WPs are presented. OCIS codes: 260.1180, 260.1440, 260.3160, 269.5430

An advanced iterative algorithm is presented to extract phase distribution from randomly and spatially nonuniform phase-shifted interferograms. The proposed algorithm divides the interferograms into small blocks and retrieves local phase shifts accurately by iterations. Therefore, the phase distribution can be calculated with high precision by eliminating the effect of tilts occurring during phase shifting. Simulated results and experiments demonstrate that the proposed algorithm exhibits high precision and converges faster than previous algorithms even when the tilt errors are up to 27.6% of the normal phase step. OCIS codes: 120.0120, 120.3180, 120.5050, 120.2650, 050.5080.

Optical properties of metal films, such as phase shift on reflection or penetration depth of electromagnetic waves into mirrors, play an important role in determining the resonance wavelength of a microcavity. We created a series of [lambda]/2 cavities with a symmetrical structure of glass/Ag/lithium fluoride/Ag by changing the thickness of the Ag film. The penetration depth at different thicknesses of Ag film was obtained from the transmittance peaks of the cavities. Phase shift on reflection at the lithium fluoride--Ag interface was calculated based on the measured optical constants. The formulation between phase shift and penetration depth was proved by experimental results, which are in good agreement with the theoretical calculations. OCIS codes: 230.4040, 310.6860.

Phase-shifting real-time holography with photorefractive [Bi.sub.12]Si[O.sub.20] crystal as holographic recording medium applied to load transmission evaluation and tension dissipation on a dried human skull under loading is presented. The applied loading stands as a simulation of isolated contraction (SIC) of some masticatories muscles. The four-frames phase-shifting technique and the unwrapping branch-cut technique were used to obtain the phase map. The quantitative results show the feasibility of the employed system in the study of microdisplacements in the skull structure provided by SIC. OCIS codes: 120.2880, 160.5320, 170.1850, 170.4580.

The interpretation of Fizeau interferograms of optical flats is not straightforward because they are composed of more than two reflections. This results in a confusing fringe pattern. There are three main contributions to the interferogram given by the reflections from the reference surface, the front and the rear surface of the sample. We present a new to the best of our knowledge solution to the problem. We use phase shifting measurements of the wave fields, which are reflected by and transmitted through the sample. This eliminates the need for the suppression of reflections by immersion or other methods. As an illustration of this method, several examples will also be presented. OCIS codes: 070.2590, 120.3180, 120.4120, 120.5050, 120.6650.

Within the modified formalism of Glauber's multiple scattering theory, we have studied the elastic scattering of deuteron with nuclei in the mass region 6 [??] B [??] 72 at intermediate [...]

We present new extensions of the two-step, triangular-pattern phase-shifting method for different numbers of phase-shifting steps to increase measurement accuracy and to analyze the influence of the number of phase-shifting steps and pitch of the projected triangular intensity-profile pattern on the measurement accuracy. Phase-shifting algorithms to generate the intensity ratio, essential for surface reconstruction, were developed for each measurement method. Experiments determined that higher measurement accuracy can be obtained with a greater number of phase-shifting steps and a lower value of pitch, as long as the pitch is appropriately selected to be divisible by the number of phase-shifting steps and not below an optimal value, where intensity-ratio unwrapping failure would occur. OCIS codes: 120.2830, 120.5050, 150.6910, 110.6880.

In quantum mechanics a localized attractive potential typically supports a (possibly infinite) set of bound states, characterized by a discrete spectrum of allowed energies, together with a continuum of scattering states, characterized (in one dimension) by an energy-dependent phase shift. The 1/[x.sup.2] potential on 0 < x < [infinity] confounds all of our intuitions and expectations. Resolving its paradoxes requires sophisticated theoretical machinery: regularization, renormalization, anomalous symmetry-breaking, and self-adjoint extensions. Our goal is to introduce the essential ideas at a level accessible to advanced undergraduates. [DOI: 10.1119/1.2165248]

Research is presented concerning the development of a compact latching structure with low losses which can be used for a phased array radar system. The small size of the superconductor ferrite phase shifter is discussed.

A demonstration is presented of multiple layer slab waveguides fabricated in polymer of silicon wafer substrates. The optical properties of the structures are theorized.

A combination of phase-shift with gray-code light projection into a three-dimensional vision system based on the projection of structured light is presented. The gray-code method is exploited to detect without ambiguity even marked surface discontinuities, whereas the phase-shift technique allows the measurement of fine surface details. The system shows excellent linearity. An overall mean value of the measurement error equal to 40 mu m, with a variability of approximately +/- mu m, corresponding to 0.06% of full scale, has been estimated. The implementation of the technique is discussed, the analysis of the systematic errors is presented in detail, and the calibration procedure designed to determine the optimal settings of the measurement parameters is illustrated.

We describe a phase-shifting out-of-plane speckle interferometer operating at 1 kHz for studying dynamic events. This system is based on a Pockels cell that is synchronized to high-speed video camera to ensure that the phase shifting occurs between frames. Phase extraction is performed by use of a standard four-frame algorithm, and temporal phase unwrapping allows sequences of several hundred absolute (rather than relative) displacement maps to be obtained fully automatically. The maximum theoretical surface velocity of 67 mu m s(super-1) is a factor of 40 greater than can be achieved with a speckle interferometer based on a conventional video camera. We test the system using a target that is displaced with constant speed in a direction normal to its surface by means of a piezoelectric transducer. The system's performance in a practical situation is illustrated with measurements on a thin plate undergoing out-of-plane deformation.

A method of linearly coded profilometry is proposed. It uses linear-structure light with isosceles triangle teeth to code the object being measured and a phase-shifting technique to decode the profile. For reducing the effect of noise more than three equally spaced samples are used, and, according to the least-squares method, the general formulas of the decoded phase are given. The experimental results of a model of a head are shown.

Profile measurement taken with liquid-crystal gratings and a phase-shifting technique is proposed, and its effectiveness is verified by experiment. The surface profile is obtained by measurement of the phase distributions of the sinusoidal gratings deformed by an object's surface. The liquid-crystal grating gives an accurate phase shift, an arbitrary projection pitch, and a constant surface brightness compared with conventional gratings such as a laser interference fringe grating and a Ronchi grating. Therefore a flexible measuring system may be developed with it. Two gratings with different pitches are used to measure an object with large steps. A two-color projection system can be used to produce such gratings simultaneously. Locally varying reflectivity on a surface can also be compensated by adjustment of the color component of the projected grating with a liquid-crystal grating. Thus the contrast in the projected grating can be made uniform, and a good profile measurement can be accomplished. OCIS codes: 120.2650, 120.3940, 120.4820, 120.5050, 120.6650, 160.3710.

We describe a method of imaging the intensity profiles of light in near-field lithographic experiments directly by using a sensitive photoresist. This technique was applied to a detailed study of the irradiance distribution in the optical near field with contact-mode photolithography carried out by use of elastomeric phase masks. The experimental patterns in the photoresist determined by scanning electron microscopy and atomic force microscopy were compared with the corresponding theoretical profiles of intensity calculated by use of a simple scalar analysis; the two correlate well. This comparison makes it possible to improve the theoretical models of irradiance distribution in the near field. Analysis of the images highlights issues in the experimental design, provides a means for the optimization of this technique, and extends its application to the successful fabrication of test structures with linewidths of [approximately]50 nm. OCIS codes: 050.5080, 110.5220, 110.0110.

The growth of electric power consumption combined with environmental pressures causing delays and cancellations of new transmission lines is forcing the Electric Utility Co. to use the existing networks with high efficiency and high reliability. Legal regulations may increase these demands even further. The use of Phase Shifting Transformers (PST) can help to control the real power flow in transmission lines and system interties. To realize a variable phase angle shift, OLTCs are used in PSTs. During the planning stage of such transformers the appropriate selection of OLTCs is of great importance for the optimal design of a PST. This paper describes the different principles of phase angle regulation and gives some guidelines for the selection of OLTCs.

A study was conducted on the exchange-correlation effects-induced energy-level shift in quasi-two-dimensional InxGa1-xAs/InGaAsP quantum wells as a function of the sheet carrier density of various biaxial compressive strain. Results show that exchange energy and correlation energy influence the energy-level shifts. Results also reveal that the shifts increase when the sheet carrier density and biaxial compressive strain increase.

A study was conducted on the influence of slab thickness on the segregation characteristics of a phase separating system. Fowler-Guggenheim approximation was accomplished on the monolayer limit to calculate the size effects. Results reveal that semi-infinite system-like phase transitions occur by changing the surface fraction. Results also indicate that the nanocrystalline region can exhibit a minimum on the free energy curve.

Near-field optical microscopy was employed in the examination of selective grown GaxIn1-xAsyP1-y multiple quantum well band-gap variations. A 550 nm lateral resolution at 1115 nm luminescence wavelength detected band gap variation. The spatial band-gap modulation observed near the (0-11) facet is attributed to material composition variation. Shifts in material composition were also found to center wavelength modulation towards lower energy.

The difference between the phase shift occurring at the object surface owing to displacement and the phase shift occurring at the observation plane of the imaging system of the interferometer is studied. Analytical expressions for the phase shift for a number of surface displacements are found. From these expressions it is found that the difference between the phase shifts at the object and the observation planes depends on the number of speckle-correlation modes in the observation plane and the product between the relative aperture and the relative defocus of the imaging system. For general displacement the results indicate that the accuracy of a phase-shift measurement with a small-aperture interferometer is limited only by the number of speckle-correlation modes at the observation plane for the case of a focused system. For a large-aperture interferometer the phase shift at the observation plane becomes sensitive to defocusing of the imaging system. Agreement between theory and experiments is observed. OCIS codes: 120.2880, 120.6160, 120.5050, 100.2650, 120.4630, 999.9999.

A study was conducted on a liquid crystal binary mixture in a contact preparation using the photothermal beam deflection method. The approach succeeded in localizing and determining crystal-smectic A and smectic A-nematic interphase boundaries. Numerical analysis also demonstrated that rear configuration photothermal probe beam approach is affected by interphase boundaries.

A proposed novel device topology is examined based on quantum wire components. The new structure prevents the conductance between an input line and a pair of output lines to be controlled by an external switching voltage. Simple electron stub tuners attached to the ring are utilized for controlling phase shifts. Results demonstrate excellent on-off features and throughput efficiencies for the quantum switch topology that is proposed.

To acquire the required resolution for 248- and 193-nm lithography, a study of attenuated phase-shifting mask (Att-PSM) technology is in progress. We performed a simulation study using a matrix method to calculate relative transmittance and the amount of phase shift of light through the PSM. However, we found that the average film composition changed with deposition time. Accordingly, optical constants were found to be a strong function of film thickness. Therefore we rearranged the relationship between deposition parameters (e.g., deposition time or gas flow rate ratio) and optical constants (e.g., refractive index and extinction coefficient) to extract the empirical formula for the optical constants with respect to film composition. To verify our simulation study, we fabricated a phase shifter based on our simulation result, which was found to have a transmittance of 8.3% and a phase shift of 179.5 [degrees]. Consequently, we obtained a reliable optimum condition for the deep-ultraviolet Att-PSM. Key words: Phase-shifting mask, attenuated type, chromium-fluoride.

The phase measurement error in an interferometric wavelength shift measurement scheme, such as that used in association with in-fiber Bragg grating sensors, has been investigated experimentally with appropriate underpinning analytical theory. It has been shown that when a lock-in amplifier is used to detect the phase shift generated by the Bragg wavelength shift, a pseudoperiodical measurement error can be introduced owing to the difference between the amplitude of the optical path difference ramp and the value of the Bragg wavelength. If the initial ramp deviation equals 20 nm, the measurement error may be as large as [+ or -]2.5% of the total measurement range. With a double-phase lock-in amplifier approach to measure the ac strain, the measurement error can be decreased to 0.4% of the total measurement range. With the real-time measured period that corresponds to the Bragg wavelength with the distorted carrier signal of the interferometer as the reference period of a digital lock-in amplifier, the effect of the initial ramp deviation can be principally avoided, and the measurement error can be kept to an acceptably low level, about 0.1% of the total measurement range.