Showing papers on "Waveplate published in 2003"

Optical alignment and spinning of laser-trapped microscopic particles

Abstract: Light-induced rotation of absorbing microscopic particles by transfer of angular momentum from light to the material raises the possibility of optically driven micromachines. The phenomenon has been observed using elliptically polarized laser beams or beams with helical phase structure. But it is difficult to develop high power in such experiments because of overheating and unwanted axial forces, limiting the achievable rotation rates to a few hertz. This problem can in principle be overcome by using transparent particles, transferring angular momentum by a mechanism first observed by Beth in 1936, when he reported a tiny torque developed in a quartz waveplate due to the change in polarization of transmitted light. Here we show that an optical torque can be induced on microscopic birefringent particles of calcite held by optical tweezers. Depending on the polarization of the incident beam, the particles either become aligned with the plane of polarization (and thus can be rotated through specified angles) or spin with constant rotation frequency. Because these microscopic particles are transparent, they can be held in three-dimensional optical traps at very high power without heating. We have observed rotation rates in excess of 350 Hz.

Circular Dichroism Imaging Microscopy: Application to Enantiomorphous Twinning in Biaxial Crystals of 1,8-Dihydroxyanthraquinone

Abstract: A microscope was constructed for imaging circular dichroism of heterogeneous anisotropic media. To avoid linear biases that are common with electronic circular polarization modulation, we chose a retrogressive solution: mechanical light modulation by rotating a linear polarizer with respect to a quarter wave plate continuously tuned by tilting to the operating wavelength. Our comparatively slow technique succeeds with near-perfect circular input and signal averaging using a CCD camera. We have applied the method to anomalously birefringent crystals of 1,8-dihydroxyanthraquinone that are shown to have intergrown mirror image domains, undetected by X-ray diffraction because the twinning complexity renders differences in anomalous dispersion, already small, unreliable. The origin of the anomalous birefringence and the assignment of the absolute configuration are discussed.

Apparatus and method of fabricating a compensating element for wavefront correction using spatially localized curing of resin mixtures

Abstract: An optical wavefront correction plate incorporates a unique, three-dimensional spatial retardation distribution utilizing the index of refraction change of resin mixture in its cured state. The optical wave plate comprises a pair of transparent plates, containing a layer of a monomers and polymerization initiators, such as resin mixture. This resin mixture exhibits a variable index of refraction as a function of the extent of its curing. Curing of the resin mixture may be made by exposure to light, such as ultraviolet light, and may be varied across and through the surface of the resin mixture to create a particular and unique three-dimensional wavefront retardation profile. The optical wave plate provides improved performance in large area mirrors, lenses, telescopes, microscopes, and ophthalmic diagnostic systems.

Experimental demonstration of photonic crystal waveplates

Abstract: We have constructed and experimentally tested a microwave half-waveplate using the dispersive birefringent properties of a bulk, two-dimensional, photonic crystal away from its band gap. Our waveplate device exhibited a 200:1 polarization contrast, limited by our experimental resolution. We anticipate that photonic crystal waveplates will have important practical applications in several areas, including integrated photonic circuits.

Single polarization optical fiber laser and amplifier

Abstract: An optically active linear single polarization device includes a linearly birefringent and linearly dichroic optical waveguide (30) for propagating light and having single polarization wavelength range (48). A plurality of active dopants are disposed in a portion (34) of the linearly birefringent and linearly dichroic optical waveguide (30) for providing operation of the waveguide in an operating wavelength range (650) for overlapping the single polarization wavelength range (48).

Roll angle interferometer by means of wave plates

Abstract: A novel roll angle interferometer using a transverse Zeeman laser (TZL) is proposed in this paper. The orthogonally linearly-polarized light from TZL is changed to be slightly elliptically-polarized light by a quarter wave plate (QWP) when the principal axis of the QWP is at a small angle with the basis of the direction of polarization. The beam then passes through a half wave plate (HWP) that is employed as a sensor. After that it is reflected by a right angle prism (RAP) and returns to the HWP again. Owing to the reasonable transformation of coordinates by the prism, the change of direction of polarization is accumulated twice when the beam passes forward and back through the HWP. Theoretical analysis and experimental results show that the sensitivity of roll measurement can reach sub-second and be improved four times than that we had reported. This system of implementing roll measurement takes the advantage of compactness, stable performance, low cost and robust to the environment disturbance.

Optical element and liquid crystal display device using the same

Abstract: There are provided a liquid crystal display device, which positively reflects, by a reflecting electrode and a light-shielding layer, light emitted from a backlight and further reflected from a light-shielding layer or a reflecting layer, and recycles the light while avoiding absorption in a linearly polarizing plate to improve the utilization efficiency of light and thus to realize a bright display screen, and an optical element for use in the liquid crystal display device. The liquid crystal display device comprises: a polarizer for converting light emitted from a back light source to linearly polarized light; a reflecting layer comprising a reflection area part for reflecting the linearly polarized light converted by the polarizer and a transmission area part for transmitting the linearly polarized light converted by the polarizer; and at least one phase difference plate which is disposed so that only the light transmitted through the transmission area part after conversion of the light source-derived light to the linearly polarized light by the polarizer is incident to the phase difference plate.

Feed-forward continuous and complete polarization control with a PLZT rotatable-variable waveplate and inline polarimeter

Abstract: A Pb/sub 1-x/La/sub x/(Zr/sub y/Ti/sub z/)/sub 1-x/4/O/sub 3/ (PLZT) electrooptic ceramic variable-rotatable waveplate and a compact inline polarimeter have been used to develop a fast feed-forward-controlled module for the continuous and complete conversion of polarization. This requires the control of only two parameters: the direction /spl theta/ and strength of the applied voltage V/sub 0/. Feed-forward control speed is fast, taking only 24 /spl mu/s. The chip plates were made by cutting T-shaped trenches into the four sides of a 500/spl times/400/spl times/300-/spl mu/m/sup 3/ PLZT chip and coating the trenches with electrodes. The PLZT waveplate is inserted into a 330-/spl mu/m gap between thermally expanded core fibers. The input polarization states are monitored by a newly developed compact and fast inline polarimeter, which is placed in front of the polarization controller. The optimum /spl theta/ and V/sub 0/ values for the required conversion are calculated by a computer, and the corresponding voltages are then applied to PLZT waveplate.

Birefringence in two-dimensional bulk photonic crystals applied to the construction of quarter waveplates

Abstract: We have experimentally measured the birefringence in bulk two-dimensional hexagonal photonic crystals in transparent spectral regions above and below the fundamental band gap. Data is presented for structures with different numbers of layers and two different air-filling fractions. We have used these data to design a photonic crystal quarter waveplate and provide independent experimental demonstrations of its operation.

Polarized light source system comprising meshing prism plates and liquid crystal display using the same

Abstract: A polarized light source system ( 20 ) includes a light guide plate ( 22 ), a light source ( 24 ), a lamp cover ( 25 ), a quarter wave plate ( 23 ), an upward prism plate ( 26 ) and a downward prism plate ( 28 ). The light guide plate defines an optical inputting surface and an optical outputting surface interconnecting therewith. The light source and the lamp cover are stationed next to the optical inputting surface. The upward prism plate stationed next to the optical outputting surface defines a plurality of upward micro-prisms ( 262 ) on a surface opposite thereto. The downward prism plate stationed next to the upward prism plate includes a brightness enhancing film ( 284 ), and a plurality of downward micro-prisms ( 282 ) on a surface facing the upward prism plate. The upward and downward micro-prisms engaged with each other. The quarter wave plate includes a reflective film on a backing surface.

Laser multiple degree-of-freedom measuring system and method

Abstract: A multi-freedom laser measuring system is composed of laser emitter, polarizing-splitting unit, 4-freedom error sensing unit, photoelectric receiver unit and signal processing unit. Said 4-freedom error sensing unit consists of quater-wavelength wave plate, optical splitter and optical reflector. The laser beam is splitted into the perpendicular mutually linear polarized light beams in two polarizing directions. The light beam received by said 4-freedom error sensing unit is splitted to two beans received by two photoelectric receiver. The linearity error of an object in two directions and the pitch angle error can be obtained after signal processing.

Device for optical linear polarization measurements with a single exposure

Abstract: The use of CCDs as focal plane detectors has changed the design concept for the polarimetric mode in the visible and, actually, also in the near infrared spectral ranges. Providing astronomical instrumentation with polarization sensitive crystal in appropriate configuration (Wollaston, Rochon, Glann-Thomson, and so on), together with half- or quarter- waveplate retarder, it is possible to determine the linear and/or circular Stokes parameters. The polarization analyser placed at the Asiago Faint Object Spectrographic Camera (AFOSC), allows simultaneous measurements of the two linear Stokes parameters usually named Q and U without any λ/2 retarder plate. Similar devices may be designed to be placed at every instrument with an accessible pupil. The paper reports details of the instrument concept and the results of observations of polarized and unpolarized standard stars, both in broad-band and spectro-polarimetry observing modes.

Polarization mode dispersion compensator, polarization mode dispersion compensating method, and its application to optical communication system

Abstract: A polarization mode dispersion compensator characterized by comprising: a compensating unit that includes a first polarization controller for subjecting a light propagated through an optical transmission path to polarization conversion and a group delay time difference imparting portion for imparting a group delay time difference to the light polarization-converted by the first polarization controller and is adapted to compensate the polarization mode dispersion imparted to the light in the propagation through the optical transmission path, a second polarization controller for subjecting the compensated light to polarization conversion so that the light may be a first linearly polarized light, a polarization separating unit for separating the light polarization-converted by the second polarization controller into the first linearly polarized light and a second linearly polarized light polarized orthogonally to the linear polarization of the first linearly polarized light, a light intensity measuring unit for measuring the intensity of the separated second linearly polarized light, and a control unit for controlling the compensating unit and the second polarization controller so that the intensity of the measured second linearly polarized light may be minimized.

Non-linear and quantum optics of a type II OPO containing a birefringent element Part 2 : bright entangled beams generation

Abstract: We describe theoretically the quantum properties of atype-II Optical Parametric Oscillator containing a birefringent plate which induces a linear coupling between the orthogonally polarized signal and idler beams and results in phase locking between these two beams. As in a classical OPO, the signal and idler waves show large quantum correlations which can be measured experimentally due to the phase locking between the two beams. We study the influence of the waveplate on the various criteria characterizing quantum correlations. We show in particular that the quantum correlations can be maximized by using optimized quadratures.

Polarization Conversion and Recycling Method and Apparatus

Abstract: A method, apparatus and system for polarization conversion and recycling by using a half-pyramid shaped reflector with multiple reflective surfaces, or said reflector assembly, to obtain a desirable polarization rotation effect. The disclosed half-pyramid reflector comprises a plurality of reflective surfaces, which are formed so that an incoming beam passing perpendicularly through the entrant surface is reflected three times inside the device and leaves the exit surface with the direction of polarization being rotated 90 degrees. The preferred embodiments of polarization:conversion systems using the invented apparatus are included. Without employing any waveplate component, the disclosed system is not sensitive to wavelength variations of the light source, temperature changes, and polarization alignment errors. Typical application of this invention includes polarization conversion and recycling for projection systems with polarization dependent spatial light modulation panels, such as LCD (Liquid Crystal Display) and LCOS (Liquid Crystal On Silicon).

Rolled web for wideband quarter-wave plate, rolled web for wideband circularly polarizing plate, rolled web for optical device, and display device

Abstract: PROBLEM TO BE SOLVED: To provide a rolled web for a long-length wideband quarter-wavelength plate having a sufficiently wide band and capable of corresponding to any size, to provide a method for efficiently manufacturing this rolled web for the quarter-wavelength plate at low cost, to provide a rolled web for a wideband circularly polarizing plate using this original rolled web for the quarter-wavelength plate, and to provide a display device, or the like. SOLUTION: This rolled web for the wideband quarter-wavelength plate consists of a long-length laminated body comprising at least an optically anisotropic layer A having a retardation of 250 to 300 nm measured at a wavelength of 550 nm and an optical anisotropic layer B having a retardation of 125 to 150 nm measured at a wavelength of 550 nm. One of the optical anisotropic layers A and B is an optically anisotropic film obtained by drawing a thermoplastic resin film, and the other consists of a film of a immobilized liquid crystal compound. This invention comprises a method for manufacturing the rolled web for the wideband quarter-wavelength plate, the rolled web for the wideband circularly polarizing plate using the wideband quarter-wavelength plate, and a display device provided with the wideband circularly polarizing plate obtained by cutting the rolled web for the wideband circularly polarizing plate. COPYRIGHT: (C)2004,JPO&NCIPI

Liquid crystal display device and surface lighting device

Abstract: To increase an amount of the light that can be used for the display efficiently in the total amount of the emitted light in the liquid crystal display device having the surface lighting device such as the front-light. The light (a) becomes the light component of the linearly polarized light by passing the retardation plate (11a). In the reflective polarizer (11b), only the light (b) that is a component of the polarization axis of the reflective polarizer (11b) passes through the reflective polarizer (11b) to enter into the end portion of the light guide (12). The light that is a component other than the component of the polarization axis of the reflective polarizer (11b) is reflected on the reflective polarizer (11b). The light reflected on the reflective polarizer (11b) changes from the linearly polarized light to the circularly polarized light by passing through the retardation plate (11a). The circularly polarized light (d) is transmitted into the light stick (10) and is reflected on the reflective film in the light stick (10). The reflected light (e) change from the circularly polarized light to the linearly polarized light by the retardation plate (11a). The linearly polarized light (f) passes through the polarization axis of the reflective polarizer (11b) to enter into the end portion of the light guide (12).

Polarization means and its position holding mechanism

Abstract: This invention provides a polarization means capable of obtaining an always clear three-dimensional image easily, correctly, and quickly and a position holding mechanism. A polarizing plate has areas for the left eye and the right eye where respective polarized lights separated by a first half wave plate enter. A second half wave plate for rotating the polarized lights in a direction opposite to that of the first half wave plate is disposed on an image display surface side for the right eye side area of the polarizing plate. A polarizing plate fixture with an arm part for holding the polarizing plate in a predetermined position is also provided.

Optical repolarizing devices

Abstract: An optical repolarizing device for transforming either a randomly polarized or unpolarized input beam into a polarized output beam. A polarization dependent beam splitter splits both polarization components of the incident signal and inserts them into an interferometer. In one arm of the interferometer, a polarization rotator, equivalent to a half waveplate, is inserted. In the other arm of the interferometer, a phase shifter is inserted. The phase shifter ensures that there are no delays between the signals in the two interferometer arms, and thus there is constructive interference when the two beams, now having the same polarization, recombine at the output of the interferometer, where a beam combiner is provided for this purpose. For unpolarized input light, the phase shifter is unnecessary.

Light control element for outputting polarised light over different angular ranges.

Abstract: A light controlling element 15 comprises vertical linear polarisers 16 positioned between transparent substrates 17, and serves to output light having a first polarisation state in a first angular range and light having a second, different polarisation state in a second, greater angular range. The linear polarisers 16 may be horizontal (Figure 5), and the system may be incorporated in a display having a display panel such as an LCD, switchable half wave plate and backlight (Figure 6). The light controller may be used in a three dimensional, autostereoscopic or dual view display. Also disclosed are manufacturing methods adhering stacked polarising sheets together, removing selected polariser regions and providing polarising material or light transmitting substrates in recesses in the element.

Three-dimensional image display device, polarization means position holding mechanism, and polarization means

Abstract: Disclosed herein is a three-dimensional image display device having an image display portion for displaying image information according to a parallax separately in a first segment and a second segment, a separate wave plate filter opposed to the first and second segments of the image display portion for converting a polarization direction of polarized light of the image information from the first segment into a direction different from a polarization direction of polarized light of the image information from the second segment, and a polarization plate having a first portion and a second portion to which the polarized lights separated by the separate wave plate filter are respectively input. The three-dimensional image display device further has a polarization plate holder for holding the positional relation between the polarization plate and the separate wave plate filter. Accordingly, a clear three-dimensional image can be always observed relatively easily, accurately, and quickly.

Synthesis of polarization-selective optical components with multilayer subwavelength structures

Abstract: In this presentation we propose the multi-layer subwavelength structures to realize the polarization-sensitive optical elements. The multi-layer structures are fabricated on such consideration that a periodic relief subwavelength structure (we call the base structure later) with depth D 1 is first prepared in a substrate with refractive index n 1 , then a dielectric material with a refractive index n 2 is directionally coated on it with thickness D 2 . With the above fabrication process the coated dielectric material alternatively covers on the ridges or fills in the grooves of base structure to form the multi-layer structures. The characteristics of the effective indices and the form-birefringence behaved in such structures were investigated. The form-birefringent wave plates and the blazed-binary polarization-selective diffractive optical elements for normal incidence were synthesized with the proposed structures. The optical behaviors included the phase retardation, diffraction efficiencies, and the polarization contrasts were numerically analyzed with rigorous electromagnetic algorithm. A quarter-wave plate for the operating wavelength of He-Ne laser (λ=632.8 nm) was fabricated and the significant optical performances was obtained.

Method for manufacturing rolled web of optical laminate, optical laminate, backlight unit and liquid crystal display

Abstract: PROBLEM TO BE SOLVED: To provide a method for manufacturing, with good productivity, a raw fabric of an optical laminate capable of condensing diffusion light into parallel light and functioning as a collimator, to provide the optical laminate and a backlight unit for a liquid crystal display using the same, and to provide the liquid crystal display. SOLUTION: In the method for manufacturing the raw fabric of the optical laminate, cholesteric liquid crystal layers 61R, 61G and 61B of Grandjean alignment which are used in combination and have a collimator function for condensing diffusion light from a light source into parallel light are serially stacked on an elongated quarter wave plate 62 and integrated with each other. The optical laminate is formed by cutting the rolled web obtained by this method. The backlight unit for the liquid crystal display has the optical laminate. The liquid crystal display has the backlight unit. COPYRIGHT: (C)2004,JPO&NCIPI

Polarized light separation optical system

Abstract: PROBLEM TO BE SOLVED: To solve a problem wherein the contrast of a projected picture is lowered because of the occurrence of leakage light in the case of analyzing light by a polarized light separation film. SOLUTION: The polarized light separation optical system which has the polarized light separation film 6a guiding polarized light from illumination optical systems 1 to 5 to a reflection type picture display element 7, also analyzes the polarized light from the picture display element, and guides it to a projection optical system 10, has structure satisfying a condition; 120°≤¾δ¾≤180° when it is assumed that a phase difference on the polarized light separation film between P polarized light and S polarized light is δ. COPYRIGHT: (C)2004,JPO&NCIPI

Nulling stellar coronagraph using liquid-crystal device

Abstract: Nulling stellar coronagraph has been proposed to detect faint objects very close to a bright point-like star, especially extra-solar planets. The principle of the nulling stellar coronagraph is to cause destructive interference for the light from a star. There have been proposed several methods for nulling interferometry. The key point of the nulling interferometry is the way to produce π-phase shift over wide range of wavelength. Here we propose a method for realizing achromatic π-phase shift utilizing polarization interference. The phase difference between two light beams that pass through different polarizers is π radians when these polarizers are placed between mutually orthogonal polarizer and analyzer. We adopt a ferroelectric liquid-crystal (FLC) device to convert the polarization direction of the incident beam. The FLC device is regarded as a birefringent device with retardation π, namely a half wave plate. The FLC device forms four-quadrant structure and is placed between the polarizer and the analyzer. By fixing the optic axes of the four-quadrant FLC suitably, it can rotate the incident linearly polarized light in parts by plus/minus 45°.

Variable quasioptical wave plate system and methods of making and using

Abstract: A wave plate (10) formed of a perforated metallic plate of a particular thickness (L) has circular holes (12) that induce a change in the polarization of an electromagnetic wave passing through the holes in the plate. By choosing the proper hole diameter, the hole spacing in orthogonal directions, and the plate thickness, the desired relative phase shift is achieved with maximum transmission and minimal reflection. Two or more axially-aligned wave plates form a variable wave plate system. By changing the relative rotational positions of the wave plates, the polarization of the electromagnetic wave passing through the system can be selectively varied.

Non-linear frequency changeover crystal

Abstract: The crystal for converting non-linear frequency includes 2-3 optical elements among the following 4 optical elements: the non-linear crystal (1), the non-linear crystal (2), 1/2 wave plate and the dual wavelength wave plate The non-linear crystal (1) and the non-linear crystal (2) are the non-linear crystals KTP with same lengths and cut along the dirction according to the II class phase match The anti-reflection film @1064nm or @1064nm &523nm are coated on the surfaces of the optical elements N pieces of the said crystals through the optical cement or the deepened optical cement forms thecrystal pile for non-linear frequency conversion, where the N is a integer The invention can compensate the stray from or the phase difference of the optical wave, and can be used as the double frequency crystal

Circularly polarized optical heterodyne interferometer for optical activity measurement of a quartz crystal.

Abstract: Phase retardation between two orthogonal circularly polarized light waves that propagate in an optical active medium is proportional to its optical activity The measurement of optical activity of a quartz depolarizer in terms of the phase difference of two orthogonal circularly polarized waves is proposed A circularly polarized optical heterodyne interferometer with a Zeeman laser to measure the optical activity of a quartz crystal is demonstrated experimentally The accuracy of the measurement is discussed In addition, the effect of elliptical polarization and nonorthogonality of linearly polarized light waves of a Zeeman laser on the optical activity measurement is analyzed

Compact hybrid integrated optical dynamic channel equalizer

Abstract: An integrated optical dynamic channel equalizer that can be employed to equalize the channel gain level in a WDM transmission line and monitor the optical channel performance. The device consists of a circulator, a dynamic gain equalizer chip and a controller. Due to the simplicity of the dynamic gain equalizer chip, which includes one 1×n multiplexer/demultiplexer, an n-channel variable optical attenuator array (VOA-n), a partially transparent dielectric reflective means and an n-channel detector array, the device is very compact and can be fabricated at low cost. By placing a quarter wave plate between the n-channel variable optical attenuator array and the partially transparent reflective means in the dynamic channel equalizer chip, the device can be rendered polarization insensitive.