Showing papers on "Waveplate published in 2007"

Systematic errors in cosmic microwave background polarization measurements

Abstract: We investigate the impact of instrumental systematic errors on the potential of cosmic microwave background polarization experiments targeting primordial B-modes. To do so, we introduce spin-weighted Miiller matrix-valued fields describing the linear response of the imperfect optical system and receiver, and give a careful discussion of the behaviour of the induced systematic effects under rotation of the instrument. We give the correspondence between the matrix components and known optical and receiver imperfections, and compare the likely performance of pseudo-correlation receivers and those that modulate the polarization with a half-wave plate. The latter is shown to have the significant advantage of not coupling the total intensity into polarization for perfect optics, but potential effects like optical distortions that may be introduced by the quasi-optical wave plate warrant further investigation. A fast method for tolerancing time-invariant systematic effects is presented, which propagates errors through to power spectra and cosmological parameters. The method extends previous studies to an arbitrary scan strategy, and eliminates the need for time-consuming Monte Carlo simulations in the early phases of instrument and survey design. We illustrate the method with both simple parametrized forms for the systematics and with beams based on physical-optics simulations. Example results are given in the context of next-generation experiments targeting tensor-to-scalar ratios r ∼ 0.01.

A W -Band Polarization Converter and Isolator

Abstract: A 95-GHz printed low-loss linear-to-circular polarizer is designed as a component of an active direct-detection millimeter-wave imaging system. The periodic printed grid structure presents different reactances to the TE and TM polarizations, resulting in equal amplitude and phase quadrature upon transmission through four parallel grids. The polarizer is measured in both a Gaussian beam system and a plane wave system, and demonstrates an axial ratio of 0.23 dB, polarization isolation of 38 dB, and transmission loss of 0.3 dB for normal incidence. The quarter-wave plate is characterized up to plusmn35deg off the optical axis, and exhibits an axial ratio better than 1 dB up to plusmn17deg off the optical axis.

Stress birefringent, space-variant wave plates for vortex illumination.

Abstract: We describe the use of stress birefringence in the creation of vortex illumination. A trifold symmetric stress pattern will provide an annular region that exhibits polarization vortices when illuminated with linearly polarized light and scalar vortices when illuminated with circularly polarized light. A finite element plane-stress model is used to analyze the space-variant anisotropy.

Electrically tunable two-dimensional liquid crystals gratings induced by polarization holography

Abstract: Two-dimensional (2D) gratings made up of an array of differently twisted nematic structures are obtained by crossed assembling of 1D polarization holograms recorded at the photoaligning substrates. The rotating linear polarization pattern, produced by the interference of two opposite circularly polarized beams, is recorded on the azo-dye doped polyimide aligning layers. The 2D gratings diffract light in different directions with different polarization states, that can be optically controlled. Orthogonal circularly and linearly polarized diffraction orders are simultaneously obtained irradiating the grating with a linearly polarized beam. An external ac voltage allows to completely control the diffracted energy distribution.

An Electrically Switchable Optical Ultrawideband Pulse Generator

Abstract: A novel electrically switchable optical ultrawideband (UWB) pulse generator that is capable of generating both Gaussian monocycle and Gaussian doublet pulses by using a polarization modulator (PolM) and a fiber Bragg grating is proposed and experimentally demonstrated. The polarity and the shape of the generated UWB pulses can be electrically switched by adjusting the voltages applied to two arbitrary wave plates (AWPs), which are incorporated at the input and the output of the PolM to adjust the polarization state of the lightwaves. The key component in the UWB pulse generator is the PolM, which is a special phase modulator that can support both transverse electric and transverse magnetic modes but with opposite phase modulation indexes. Depending on the polarization state of the incident lightwave to the PolM that is linearly polarized and aligned to one principle axis of the PolM or circularly polarized, UWB monocycle or doublet pulses are generated. The polarity of the UWB pulses can be electrically switched by adjusting the voltages applied to the AWPs. The proposed system is implemented, and the generation of UWB monocycle and doublet pulses is experimentally demonstrated. Gaussian monocycle and doublet pulses with a fractional bandwidth of about 150% and 160% are experimentally generated. The proposed electrically switchable optical UWB pulse generator has the potential for applications in UWB communications and radar systems that employ pulse polarity modulation and pulse shape modulation schemes.

Mimicking optical activity for generating radially polarized light.

Abstract: We propose a new scheme for generating radially polarized light by mimicking optical activity using linear birefringence. It involves a birefringent spirally varying retarder sandwiched between two orthogonally oriented quarter-wave plates. Using Poincare sphere representation, we show that the polarization transformation of such a scheme is equivalent to that of a spirally varying optical activity and is capable of generating radially polarized light. We demonstrate the proof-of-concept using y-cut crystalline quartz.

Measurement of surface figure of plane optical surfaces with polarization phase-shifting Fizeau interferometer

Abstract: A Fizeau interferometer based set up for measurement of surface forms of plane optical surfaces has been discussed. Phase shifting interferometry has been applied using polarization phase shifter. A linearly polarized (632.8 nm) He–Ne laser has been used as the source. Light reflected from the object and the reference/master surfaces are made circularly polarized in opposite senses by means of two properly oriented quarter wave retardation plates placed at appropriate positions, one inside and other outside the interference cavity of the interferometer, and phase shifts are introduced between the object and the reference/master waves by varying angular orientation of a polarizer/analyzer. Final result is made free from any residual wave-front aberrations introduced by the (intra-cavity) wave plate by subtracting phase values obtained by PSI technique between a high optical quality master surface and the reference surface from that obtained for the test object surface with respect to the same reference surface for each point of the interference field. Results are shown for a plane surface. Advantages of the technique presented are linearity and high accuracy in phase stepping, no perturbation of the interference cavity during the phase shifting and possibility of real time or dynamic interferometry.

Two-dimensional polarization rotator using a twisted-nematic liquid-crystal display.

Abstract: We present a novel configuration for a twisted-nematic liquid-crystal display (TN-LCD) that makes it operate as a controllable polarization rotator. We extend a previously reported polarization rotator configuration using a zero-twist LCD inserted between two quarter-wave plates. We first operate the TN-LCD in the polarization eigenvector configuration and show how this system can act as an equivalent voltage-controlled wave plate. Next we incorporate this wave plate into the optical rotator configuration. We show that the plane of polarization of the transmitted light can be rotated as a function of the phase introduced by the display. Finally, we create a 2D polarization mask where different areas of the TN-LCD form different polarization states. Experimental results are included.

Design and Demonstration of an Infrared Meanderline Phase Retarder

Abstract: We compare design and measurements for a single-layer meanderline quarter-wave phase retarder, operating across the wavelength range from 8 to 12 micrometers (25 to 37.5 THz) in the infrared. The structure was fabricated using direct-write electron-beam lithography. With measured frequency-dependent material properties incorporated into a periodic-moment-method model, reasonable agreement is obtained for the spectral dependence of axial ratio and phase delay. As expected from theory, the single-layer meanderline design has relatively low throughput (23%), but with extension to multiple-layer designs, the meanderline approach offers significant potential benefits as compared to conventional birefringent crystalline waveplates in terms of spectral bandwidth, angular bandwidth, and cost. Simple changes in the lithographic geometry will allow designs to be developed for specific phase retardations over specified frequency ranges in the infrared, terahertz, or millimeter-wave bands, where custom-designed waveplates are not commercially available.

Laminated optical film, and liquid crystal panel and liquid crystal display apparatus using the laminated optical film

Abstract: Provided are a laminated optical film capable of enhancing a contrast ratio in an oblique direction remarkably while enhancing viewing angle characteristics when being used in a liquid crystal display apparatus or the like, and a liquid crystal panel and a liquid crystal display apparatus using the laminated optical film. The laminated optical film of the present invention includes a polarizer, a first optical compensation layer, and a second optical compensation layer in the stated order, in which the first optical compensation layer has a refractive index profile of nx>nz>ny and is placed so that a slow axis direction thereof is substantially parallel to or substantially perpendicular to an absorption axis direction of the polarizer, and the second optical compensation layer converts linearly polarized light into circularly polarized light or circularly polarized light into linearly polarized light in a visible light region.

Liquid-crystal-based linear polarization rotator

Abstract: A liquid-crystal (LC)-based polarization rotator which can rotate the polarization axis of an incident linearly polarized light from 0° to 90° is demonstrated. In the LC cell, the top substrate has a uniform rubbing but the bottom substrate has two orthogonal rubbings which are separated by a nonrubbing zone. Between these two rubbed strips, the LC directors twist continuously from 0° to 90°. As a result, the optic axis of the incident linearly polarized light can be rotated continuously depending on the beam position.

Polarized light emitting diode and use thereof

Abstract: Provided is a light emitting diode (LED). The LED, in one embodiment, includes a reflective layer located over a substrate and a quarter wave plate emitter layer located over the reflective layer. The quarter wave plate emitter layer, in this embodiment, is substantially crystalline in nature, and further wherein an extra-ordinary axis of the quarter wave plate emitter layer is located in a plane thereof. The LED, in this embodiment, further includes a transmissive/reflective polarization layer located over the quarter wave plate emitter layer, wherein a transmission direction of the transmissive/reflective polarization layer is oriented at about 45 degrees with respect to the extra-ordinary axis.

Retardation plate and its manufacturing method, circularly polarizing plate and 1/2 wave plate using same, and a reflective liquid crystal display

Abstract: A method is provided for manufacturing a wide band retardation plate which gives uniform phase difference characteristics to incident light over the whole visible wavelength region, and which, as it permits selection of raw materials regardless of whether they have a positive or negative intrinsic double refraction value, allows a wide selection of raw materials. For this purpose, the method comprises a machine direction-stretched film-forming step for transporting and stretching in an identical direction to the transport direction, a Material A of two or more materials having different positive intrinsic double refraction values to form a machine direction-stretched film, a transverse direction-stretched film-forming step for transporting and stretching in a perpendicular direction to the transport direction, a Material B of the aforesaid two or more materials to form a transverse direction-stretched film, and a lamination step for laminating the machine direction-stretched film and the transverse direction-stretched film.

Laser, six freedom simultaneous measuring apparatus

Abstract: A laser 6-DOF simultaneous measuring device, belongs to technical field of photoelectric detection, the utility model comprises computer(16), fixed unit(101) and 6-DOF sensing unit(201), these three parts form a system, which utilizes single collimated laser beam as reference for measurement, realizes linearity error positioning in two directions as well as 6-DOF simultaneous measurement of pitch angle deflection angle and rolling angle. 6-DOF sensing unit(201) of this system comprises reflector(20), quarter wave plate(19) and semitransparent semireflecting mirror(18), wherein reflector(20) serves as sensing device for two-dimensional linearity error and positioning error, quarter wave plate(19) serves as sensing device for rolling angle, semitransparent semireflecting mirror(18) serves as sensing device for pitch angle and deflection angle. The whole measuring system has simple optical structure, cable free movable measuring head, small volume, light weight, high precision and high speed etc.

Wide field of view, compact collimating apparatus

Abstract: A compact, lightweight, multi-wavelength display system which can be used as a collimating eyepiece. A first polarization selective optical element reflects light have one linear polarization state while transmitting light having the orthogonal linear polarization state. A first quarter-wave plate transforms the linearly polarized light to a circular polarization. A combining optical element with a partially reflective surface reflects a portion of the transformed light and transmits a portion of die transformed light. A second quarter-wave plate transforms the circularly polarized light back to a linear polarization. A second polarization selective optical element reflects light have one linear polarization state while transmitting light having the orthogonal linear polarization state.

Methods and Apparatus for Compressed Imaging Using Modulation in Pupil Plane

Abstract: Methods and apparatus are provided for compressed imaging by performing modulation in a pupil plane. Image information is acquired by modulating an incident light field using a waveplate having a pattern that modifies a phase or amplitude of the incident light field, wherein the waveplate is positioned substantially in a pupil plane of an optical system; optically computing a transform between the modulated incident light field at a plane of the waveplate and an image plane; and collecting image data at the image plane. The transform can be, for example, a Fourier transform or a fractional Fourier transform

Compensation schemes for lcos projection systems using form birefringent polarization beam splitters

Abstract: An LCoS projection system provides a form birefringent polarization beam splitter (PBS) having an output modulator port, a light modulating panel, and a biaxial compensation element between the output modulator port and the light modulating panel. In one embodiment, the biaxial compensation element is a biaxial quarter wave plate. In another embodiment, the biaxial compensation element includes a uniaxial quarter wave plate and a biaxial trim retarder. The biaxial compensation element provides improved contrast performance.

Poincaré Sphere Method for Optimizing the Phase Modulation Response of a Twisted Nematic Liquid Crystal Display

Abstract: We report an experimental procedure for achieving spatial modulation of the phase of an input wave field with an off-the-shelf twisted nematic liquid crystal display. This method involves illumination of an addressed liquid crystal display (LCD) with circularly polarized light and measurement of the Stokes parameters of the outgoing beam as the applied voltage is changed. The analysis of the distribution of the polarization states in the S1-S2 plane suggests a simple way to optimize the liquid crystal phase response by means of a properly oriented quarter wave-plate followed by an analyzer. Laboratory results for a commercial display are presented. A phase modulation depth of 240deg is obtained at 514 nm with a residual intensity variation which is lower than 4%

Conversion of circularly polarized light into linearly polarized light in anisotropic phase gratings using photo-cross-linkable polymer liquid crystals

Abstract: The polarization state of the diffraction light from the polarization holographic grating on varying the polarization conditions of the writing beams has been investigated on the basis of Jones theory. The authors found that the polarization holographic grating, which was fabricated by irradiating the two writing beams with around 0.2 of polarization ellipticity, could convert circularly polarized light into linearly polarized light, and the anisotropic phase grating under above-mentioned condition was really fabricated using the photo-cross-linkable polymer liquid crystal. This function, not observed in the conventional polarization gratings, should be widely applied as highly functionalized optical devices.

High resolution autosterioscopic display

Abstract: A high resolution autostereoscopic display includes: a backlight; a display panel forming an image using the backlight light; a viewing zone separator separating viewing zones of right and left eye images of the display panel; a polarizer polarizing the light from the display panel into first polarized light; a polarization switch converting the first polarized light into second polarized light that is polarized in a different direction; and a birefringent plate including a refractive index that varies consistent with the polarization of incident light. Images corresponding to odd and even numbered column fields are formed with the first and second polarized light, time-sequentially. The birefringent plate shifts the second polarized light with respect to the first. A three-dimensional image with the full resolution of the display panel is formed by images corresponding to an odd-numbered and even-numbered column field with the first and shifted second polarized light, respectively.

Method and device of light splitting, image-forming and synchronous phase-shifting in optical interferometry

Abstract: The invention discloses a method called optical interferometry about spectrometer, imaging and simultaneous phase-shifting: enlarge polarization laser beam emitted by laser source and get linearly polarized planer source, then, enter the interference system of linearly polarized planer source and get a interference field where testing wavefront and reference wavefront have collinear beam and polarization direction is vertical each other beam of light of interference field is divide ed into 4 beams of light whose space is distributed symmetrically and whose intensity is symmetrical after passing through 1/4 wave plate and light dividing system of combined glass prism, the four beams of light projects to ccd focus plane after it is through polaroid analyzer, thus, we get four interference fringe pattern whose phase move 90 degrees after a sampling at a high speed At the same time, it discloses the device using the method According to the device and method of this invention, the principle is clear and the method is simple, the device possesses miniaturization It realizes dynamic measuring whose optic interference is high-accuracy at the scene; it is simpler and more convenient to measure the course

Laminated wave plate and optical pickup using the same

Abstract: A conventional broadband quarter-wave plate has not completely solved the wavelength dependence and has different efficiencies of shifting the phase by 90° depending on the wavelengths, and therefore has a problem that it cannot fulfill the strict specifications on the optical characteristics which are demanded of a wave plate from a viewpoint of the optical efficiency and the like in an optical pickup device compatible with a plurality of different wavelengths. To provide a wave plate which completely functions as a quarter-wave plate with respect to a plurality of different wavelengths and an optical pickup using that wave plate to solve the problem, the present invention provides a laminated wave plate, wherein a wave plate with a phase difference α and a wave plate with a phase difference β with respect to monochromatic light with a wavelength λ are laminated in such a way that directions of optical axes of said plates intersect each other, so that the laminated wave plate, as a whole, functions as a quarter-wave plate, and which is characterized in that a relationship between the α and the β satisfies the following formulas: (3/2)×π≠α−2×π×(m−1) π≠β−2×π×(n−1), wherein: each of m and n is a positive integer.

Waveplate analyzer using binary magneto-optic rotators.

Abstract: We demonstrate a simple waveplate analyzer to characterize linear retarders using magneto-optic (MO) polarization rotators. The all-solid state device can provide highly accurate measurements for both the retardation of the waveplate and the orientation of optical axes simultaneously.

Method and apparatus for measuring 1/4 wave plate phase delay and quick shaft direction

Abstract: A method and device for measuring displacement delay and axle direction of 1/4 wave-plate. Its principle is: uses light intensity detecting technique of elliptical polarization, setslambda/4 Fresnel double diamond and 1/4 wave-plate between polarizer and analyzer in turn, rotates wave-plate and analyzer to different position and detecting output light intensity, finally achieves displacement delay and axle direction of 1/4 wave-plate. The invention can detect displacement delay and axle direction of 1/4 wave-plates with different wavelength in a wide spectral range, which has high detecting precision, convenient operation and automatic measurement.

Polarimetric imaging cross talk effects from glue separation between FPA and micropolarizer arrays at the MWIR

Abstract: We have numerically and experimentally determined the effect of crosstalk from adjacent gold wiregrid micropolarizer pixels in a midwave infrared (MWIR) focal plane array (FPA). Fabrication of a snapshot polarization-imaging device involves gluing a micropolarizer array substrate on top of an FPA. We evaluated several arrays of super-cells of four pixelated polarizers by modeling the near fields behind the devices. Each polarizer in the super-cell is oriented to allow solving three Stokes parameters by themselves or four Stokes parameters in conjunction with a birefringent waveplate. In addition, we fabricated sets of super-cells for determining optimum polarizer-FPA separation. Modeling and empirical data indicate cross talk between the adjacent pixels at several microns after crossing the polarizer plane. Cross talk between adjacent pixels increases uncertainty in the measured polarization states of a scene of interest. Data shows that the extinction ratio will decrease by 17% when moving the FPA from 0.5 mm to 1.0 mm away from the polarizer. These changes in extinction ratio are important given that typical glue separation is approximately 10 mm.

Polarization analysis with digital holography by use of polarization modulation for single reference beam

Abstract: Digital holography is applied to analyze the spatial distribution of the polarization state of light transmitted through anisotropic objects by successive hologram recording using polarization switching of the reference wave by an optical fiber Faraday rotator. For a preliminary object to confirm the principle of polarization analysis, a quarter wave plate (QWP) is used, and the distribution of the polarization ellipse over the object surface is analyzed for various azimuths of the QWP. By inserting a polarizer into a part of the object wave after the object as a reference area, a phase drift of the reference waves caused by polarization switching and/or environmental disturbances can be evaluated and compensated for by using the reference area. The principal axis and ellipticity are calculated and compared with their theoretical values. A good agreement between the experimental and theoretical values is observed. For an application, a photoelastic effect induced in a stressed PMMA specimen is also investigated.

Polarization-dependent effects of refractive index change associated with photoisomerization investigated with Z-scan technique

Abstract: The Z-scan technique is used to investigate the effects of refractive index change (RIC) associated with photoisomerization for two cases: in which the sample is pumped and probed by the same elliptically polarized light, and in which the sample is pumped by a linearly polarized light and probed by another linearly polarized light. Both experimental and theoretical results show that for the first case, this effect depends upon the polarization of the light; that is, when the polarization changes continuously from circularly polarization to linearly polarization, the effects of RIC becomes stronger. For the second case, the effect is similar to the effects of saturable Kerr effect, whose nonlinear coefficient n2 is measured.