Showing papers on "Polarization rotator published in 2004"

Strong polarization in the optical transmission through elliptical nanohole arrays.

Abstract: Strong polarization dependence is observed in the optical transmission through nanohole arrays in metals. It is shown that the degree of polarization is determined by the ellipticity and orientation of the holes; the polarization axis lies perpendicular to the broad edge of the ellipse. Furthermore, the depolarization ratio shows a squared dependence on the aspect ratio of the holes, which is discussed in terms of coupling into and out of the surface plasmon modes. The observed results will be useful for tailoring the polarization behavior of metallic nanophotonic elements in many applications, including surface plasmon enhanced optical sensing and ultrafast optical switching.

Absolutely single polarization photonic crystal fiber

Abstract: An optical fiber that guides only one polarization mode of a light signal is realized by using highly birefringent pure silica photonic crystal fiber. The fiber guides only one polarization mode at wavelengths longer than 1450 nm. A polarization dependent loss of 196 dB/km with a 28 dB/km transmission loss is achieved at a wavelength of 1550 nm.

Engineering space-variant inhomogeneous media for polarization control

Abstract: Novel devices for converting a linear polarization state to radial or azimuthal polarization states are realized by use of space-variant inhomogeneous media on a subwavelength scale. The two designs presented use form birefringence to locally transform the polarization state. The devices are fabricated in a GaAs substrate for operation in the far-infrared wavelength range. The experimental characterization is in good agreement with the designs, demonstrating high conversion efficiency.

Polarization maintaining large mode area photonic crystal fiber

Abstract: We report on a polarization maintaining large mode area photonic crystal fiber Unlike, previous work on polarization maintaining photonic crystal fibers, birefringence is introduced using stress applying parts This has allowed us to realize fibers, which are both single mode at any wavelength and have a practically constant birefringence for any wavelength The fibers presented in this work have mode field diameters from about 4 to 65 micron, and exhibit a typical birefringence of 15·10-4

Complex degree of mutual polarization.

Abstract: Starting from the concepts of coherence and polarization, we generalize the conventional degree of polarization, introducing a two-point parameter, the complex degree of mutual polarization V, which is defined in terms of measurable quantities. We demonstrate the physical significance of this new quantity for the case of fully correlated, pure states of polarization at the two points, showing that the magnitude of V is a measure of the similarity between the states of polarization at two different points in space.

Nonlinear polarization rotation and orthogonal polarization generation experienced in a single-beam configuration

Abstract: Nonlinear polarization rotation and generation of a polarization component orthogonal to the input beam were observed along fourfold axes of YVO4 and BaF2 crystals. We demonstrate experimentally that in both crystals the angle of rotation is proportional, at low intensities, to the square of the product of the input intensity and the crystal length and is the result of simultaneous action of two third-order processes. This type of nonlinear polarization rotation is driven by the real part of the cubic susceptibility. The recorded energy exchange between the two orthogonal components can exceed 10%. It is to our knowledge the highest energy-conversion efficiency achieved in a single beam nonresonant χ(3) interaction. A simple theoretical model is elaborated to describe the dependence of nonlinear polarization rotation and orthogonal polarization generation on the intensity of the input beam at both low- and high-intensity levels. It reveals the potential contributions from the real and the imaginary parts of the susceptibility tensor. Moreover, this kind of measurement is designed to permit the determination of the magnitude and the sign of the anisotropy of the real part of third-order nonlinearity in crystals with cubic or tetragonal symmetry on the basis of polarization-rotation measurements. The χxxxx(3) component of the third-order susceptibility tensor and its anisotropy sign and amplitude value for BaF2 and YVO4 crystals are estimated and discussed.

Experimental study of polarization properties of highly birefringent photonic crystal fibers.

Abstract: We analyze experimentally the polarization properties of highly nonlinear small-core photonic crystal fibers (PCFs) with no intentional birefringence. The properties of recently emerged polarization maintaining PANDA PCFs are also investigated. The wavelength and temperature dependence of phase and group delay of these fibers are examined in the telecommunications wavelength range. Compared to a standard PANDA fiber, the polarization characteristics and temperature dependence are found to be qualitatively different for both types of fibers.

SU5: a calibrated variable-polarization synchrotron radiation beam line in the vacuum-ultraviolet range

Abstract: SU5 is a high-resolution variable-polarization synchrotron radiation (SR) beam line with which linear and circular dichroism experiments are performed in the vacuum ultraviolet (VUV) range (5-40eV), based on an electromagnetic crossed undulator called the Onduleur Plan/Helicoidal du Lure a Induction Electromagnetique (OPHELIE). To get precise knowledge of the polarization state of the emitted SR and to take into account the polarization transformations induced by reflection on the various optics, we set up an in situ VUV polarimeter to provide a precise and complete polarization analysis of the SR atthe sample location. The overall measured polarization performances were highly satisfactory, with measured linear polarization rates of more than 98% (83%) in the vertical (horizontal) linear polarization mode and an average 92.1% (95.2%) circular polarization rate for the right- (left)-handed circular polarization mode, which, to our knowledge, are the highest reported values in the VUV range. Despite some uneven photon energy efficiency, the OPHELIE crossed undulator behaves as expected in terms of polarization, permitting full control of the emitted polarization by manipulation of the vertical-to-horizontal magnetic field ratio (rho(und)) and the relative longitudinal phase (phi(und)).

Zero voltage Freedericksz transition in periodically aligned liquid crystals

Abstract: Patterned alignment layers have been created through an approach using polarization holography and a photopolymerizable alignment layer. This technique enables continuously periodic boundary conditions on planar surfaces. Polarization gratings have been created using polarization interference from incident right-handed and left-handed circular polarization exposure conditions. A simple phenomenological model is derived to show that the Freedericksz threshold voltage vanishes when the cell gap and grating pitch are comparable.

Degree of polarization surfaces and maps for analysis of depolarization

Abstract: The concept of degree of polarization surfaces is introduced as an aid to classifying the depolarization properties of Mueller matrices. Degree of polarization surfaces provide a visualization of the dependence of depolarization on incident polarization state. The surfaces result from a non-uniform contraction of the Poincare sphere corresponding to the depolarization properties encoded in a Mueller matrix. For a given Mueller matrix, the degree of polarization surface is defined by moving each point on the unit Poincare sphere radially inward until its distance from the origin equals the output state degree of polarization for the corresponding input state. Of the sixteen elements in a Mueller matrix, twelve contribute to the shape of the degree of polarization surface, yielding a complex family of surfaces. The surface shapes associated with the numerator and denominator of the degree of polarization function are analyzed separately. Protrusion of the numerator surface through the denominator surface at any point indicates non-physical Mueller matrices. Degree of polarization maps are plots of the degree of polarization on flat projections of the sphere. These maps reveal depolarization patterns in a manner well suited for quantifying the degree of polarization variations, making degree of polarization surfaces and maps valuable tools for categorizing and classifying the depolarization properties of Mueller matrices.

A novel polarization splitter based on the photonic crystal fiber with nonidentical dual cores

Abstract: A novel polarization splitter based on photonic crystal fibers (PCFs) with two nonidentical cores is proposed. The two highly birefringent cores are vertically arranged to obtain polarization selective coupling. The horizontal polarization exchanges its energy between the two cores. However, the vertical polarization shows little coupling between the two cores. This is achieved in single-material glass waveguides for the first time to our knowledge. The PCF-based polarization splitter exhibits many advantages such as shorter length, high extinction ratio, and wide bandwidth over its counterparts.

Semiconductor microcavity as a spin-dependent optoelectronic device

Abstract: We demonstrate experimentally that stimulated scattering of exciton--polaritons in a semiconductor microcavity in the strong coupling regime results in a dramatic build-up of the circular polarization degree of light emitted by the cavity. Moreover, we show that the polarization of the emitted light can be different from the polarization of the pumping light, e.g., pumping with a linearly polarized beam we detect a circularly polarized emission. This proves that the stimulated scattering of polaritons selects and amplifies a given polarization and inhibits all spin-relaxation processes. We believe that strong coupling microcavities can be used as building blocks for spin-dependent optoelectronic devices aimed at manipulations with the polarization of light on a micro- to nano-scale.

Polarization conversion in ring resonator phase shifters

Abstract: The effect of the polarization rotation induced by curved waveguides on the spectral behavior of phase shifter ring resonators is investigated both theoretically and experimentally. At resonance the polarization rotation that takes place in curved waveguides is strongly enhanced. The effect can be detrimental, or it can be exploited for new devices. The ring vectorial transfer function is derived, together with the conditions for the total conversion of TE polarization into TM polarization. These conditions are verified experimentally.

Wavelength dependent birefringence of surface plasmon polaritonic crystals

Abstract: A periodic array of elliptical nanoholes in a metal film acts as a thin two-dimensional birefringent crystal with wavelength dependent orientation of principal polarization eigenstates, the property which is not encountered in natural crystals. The transmission spectrum of such metallic nanostructures can be controlled in a wide range by selecting the polarization of incident and transmitted light.

Object identification medium and identification method

Abstract: An identification medium (10a) includes a first two-layered body (101) consisting of a right circular polarization polymer cholestric liquid crystal layer (11) reflecting light of particular right circular polarization and a left circular polarization polymer cholestric liquid crystal layer (12) reflecting light of particular left circular polarization. The identification medium (10a) is attached to an object (30) and by visual watch through a simplified judgment device (20) having a filter (21) passing only light of right circular polarization and a filter (22) passing through only light of left circular polarization, it is possible to see the color of the right circular polarization polymer cholestric liquid crystal layer (11) at the side of right circular polarization filter (21) and the color of the left circular polarization polymer cholestric liquid crystal layer (12) at the side of the left circular polarization filter (22). Thus, by checking a peculiar phenomenon caused by the identification medium (10a) which cannot be reproduced normally, it is possible to easily and surely authenticate the object (30).

Polarization-independent tunable fiber comb filter

Abstract: We have demonstrated a polarization-independent tunable fiber comb filter by using both polarization-diversity loop technique and birefringence tuning technique. The proposed apparatus consists of one polarization beam splitter, polarization-maintaining fibers, and three waveplates (one quarter-wave plate and two half-wave plates). The capability of continuously tuning the output spectrum was theoretically analyzed and then experimentally verified.

Systems using polarization-manipulating retroreflectors

Abstract: Measurement systems that separate polarization components can use retroreflectors to preserve or transform polarization and avoid unwanted mixing of the polarization components. A suitable retroreflector can include a coated cube corner reflector with retardation plates having a slow axis set at a non-zero angle away from 45° with the directions of linearly polarized component beam. The non-zero angle can be set in situ to minimize polarization mixing in a measurement system. Alternatively, a cube corner reflector with one or more polarization manipulating elements controls the polarization of a reflected beam to preserve or transform the polarization of an incident beam.

Optical-injection-induced polarization switching in polarization-bistable vertical-cavity surface-emitting lasers

Abstract: We present a simple quasianalytical formalism for static polarization-resolved light-current characteristics of dual polarization mode vertical-cavity surface-emitting lasers (VCSELs) under optical injection. Dynamics of optical-injection-induced polarization switching are analyzed and simple analytical estimates for the polarization switching time obtained in particular cases. The results suggest the possibility of ultrafast polarization switching, implying that optical-injection-induced polarization switching in VCSELs can operate as a fast flip-flop operation.

Polarization sensitive behaviour of the band-edge transitions in ReS2 and ReSe2 layered semiconductors

Abstract: The polarization sensitive behaviour of the band-edge transitions in ReS2 and ReSe2 layered compounds was studied using polarized-transmission and polarized-thermoreflectance (PTR) measurements with polarization angles from θ = 0° (-axis) to θ = 90° (-axis) at 300 K. The polarization dependence of the polarized energy gaps of ReS2 and ReSe2 shows a sinusoidal-like variation with respect to the angular change of the linearly polarized light. The angular dependences of the polarized energy gaps of ReS2 and ReSe2 were evaluated. The polarization sensitive behaviour of the band-edge excitons in rhenium disulfide and diselenide was characterized using angular dependent PTR measurements from θ = 0° to 90°. The polarized transition intensities of the band-edge excitons (E1ex and E2ex) of ReX2 (X = S, Se) demonstrate a sinusoidal variation with respect to the angular change of the linearly polarized light. The angular dependence of the polarized transition probabilities of E1ex and E2ex is analysed. The polarization sensitive behaviours of ReX2 (X = S, Se) layers are discussed.

Electro-optical dimming system

Abstract: An electronic dimming system for use in projection displays is provided. In a first embodiment, the dimming system comprises a first non-absorbing polarizer, a variable polarization rotator, a second non-absorbing polarizer and a heat absorber. The first non-absorbing polarizer receives light from a light source and passes the light of a selected polarization to the variable polarization rotator. The variable polarization rotator selectively rotates the polarization of the received light. The light passes from the variable polarization rotator to the second non-absorbing polarizer. The second non-absorbing polarizer passes only light of a second selected polarization. The light that passes the second non-absorbing polarizer is passed to the display, where it is used to illuminate the display. The system provides the ability to control the amount of light passed to the display by selectively rotating the polarization of the light with the variable polarization rotator.

Generation and analysis of state of polarization using tunable optical polarization rotators

Abstract: This application describes optical monitoring devices and applications in optical systems for monitoring various optical parameters of light, including the signal to noise ratio, the degree of polarization, and the differential group delay (DGD)

Statistics of the DGD in PMD emulators

Abstract: We give the statistics of the differential group delay at the output of a polarization-mode dispersion emulator made of a chain of fiber sections with constant birefringence, fixed and arbitrarily selected lengths, and randomly oriented polarization controllers in between.

Polarization singularities in optical lattices.

Abstract: Polarization singularities are shown to be unavoidable features of three-dimensional optical lattices. These singularities take the form of lines of circular polarization, C lines, and lines of linear polarization, L lines. The polarization figures surrounding a C line (L line) rotate about the line with winding number ±1/2 (±1). C and L lines permeate the lattice, meander throughout the unit cell, and form closed loops. Surprisingly, every point in a linearly polarized optical lattice is found to be a singularity about which the surrounding polarization vectors rotate with an integer winding number.

High-power CW linearly polarized all-fiber Raman laser

Abstract: We demonstrate a high-power continuous-wave linearly polarized all-fiber Raman laser. The maximum Stokes output power of 4.7 W at 1120-nm wavelength with conversion slope efficiency of 87% was achieved. It is shown that Raman laser threshold greatly depends on pump polarization degree while Raman laser polarization depends on the design of Raman converter rather than on polarization of the pump laser. Slope efficiency was found to be independent on pump polarization degree.

Vector theory of cross-phase modulation: role of nonlinear polarization rotation

Abstract: We develop a vector theory of cross-phase modulation (XPM) capable of describing nonlinear coupling between two pulses of different wavelengths and arbitrary states of polarization. We focus for simplicity on the pump-probe configuration and use it to investigate the temporal and spectral polarization effects occurring inside an optical fiber. Using the Stokes-vector formalism we show that the probe polarization changes in general through XPM-induced nonlinear polarization rotation. In the absence of dispersion-induced probe broadening, such nonlinear changes in the probe polarization do not affect the temporal shape of the probe pulse but produce a multipeak spectrum whose different spectral peaks have different states of polarization. When dispersive effects are included, even the shape of the probe pulse becomes polarization dependent, and different parts of the pulse develop different states of polarization. Such nonlinear polarization effects lead to novel phenomena such as polarization-dependent compression and splitting of the probe pulse.

Control of polarization switching in vertical coupled-cavities surface emitting lasers

Abstract: We report a novel three-contact vertical-cavity surface-emitting laser (VCSEL) for use in polarization-sensitive optical applications. The device consists of two vertical cavities, coupled by a common mirror. We demonstrate that one can independently choose both the power of the output beam-through the current in the first cavity-and the polarization state-through the bias applied to the second cavity. The control of the polarization state is performed with a control voltage in the range -2 to 0 V. Within this interval, the structure exhibits a bistable behavior. We present the very first experimental proof of nonthermal, electrically induced polarization switching in coupled-cavities VCSELs.

Polarization recovery system using redirection

Abstract: A polarization recovery system includes a polarizing beam splitter transmitting light of a useful polarization in an output direction and reflecting light of a non-useful polarization in a first orthogonal direction substantially orthogonal to the output direction. An initial reflector may reflect the non-useful polarization light in a second orthogonal direction substantially orthogonal to the output direction and the first orthogonal direction, and a final reflector may reflect the non-useful polarization light in the output direction. The non-useful polarization light may be rotated substantially to light of the useful polarization by the initial and final reflectors.

Highly polarized photonic crystal fiber laser

Abstract: We report on the design of a polarization maintaining, double-clad, Yb doped photonic crystal fiber and demonstrate its lasing properties. The polarizing properties of the fiber rely on birefringence and differential loss introduced by an anisotropic hole structure. Due to a slight leak from the core to the inner cladding only ~80% of the output light is in the core mode. We have demonstrated 2.9W of output in this mode with a polarization ratio in excess of 200:1.

Method and device for stabilizing the state of polarization of a polarization multiplexed optical radiation

Abstract: A device (100) and method for stabilizing the polarization of a polarization multiplexed optical radiation comprising an identified channel which is provided with a pilot signal. The device (100) and method are based on providing to the polarization multiplexed optical radiation a controllable polarization transformation; measuring the optical power of a polarized portion of the identified channel downstream the polarization transformation; controlling, responsively to said optical power, the controllable polarization transformation so that the identified channel downstream the polarization transformation has a predefined polarization azimuth; providing to the optical radiation downstream the polarization transformation a further controllable polarization transformation; measuring the optical power of a polarized portion of the identified channel downstream the further controllable polarization transformation; controlling, responsively to said optical power, the further controllable polarization transformation so that the identified channel downstream the further controllable polarization transformation has a predefined state of polarization (SOP our).