Showing papers on "Polarization rotator published in 2012"
TL;DR: In this article, a three-layer chiral metamaterial is constructed by using two layers of four mutually rotated resonators and a subwavelength mesh sandwiched symmetrically between these layers.
Abstract: A three-layer chiral metamaterial is constructed by using two layers of four mutually rotated resonators and a subwavelength mesh sandwiched symmetrically between these layers The resulting structure is an ultrathin, transparent, and polarization angle independent 90° polarization rotator Due to the electromagnetic tunneling effect exerted by the negative permittivity mesh, a cross-polarization conversion efficiency of 99% and 93% is achieved numerically and experimentally The structure is modeled using the effective medium theory and then the transfer matrix method is applied to demonstrate the existence of the tunneling resonance theoretically
197 citations
10 Dec 2012
TL;DR: A monolithic dual-polarization quadrature phase-shift keying (QPSK) modulator based on a silicon photonic integrated circuit (PIC) that consists of four high-speed silicon modulators, a polarization rotator, and a polarization beam combiner is presented.
Abstract: We present a monolithic dual-polarization quadrature phase-shift keying (QPSK) modulator based on a silicon photonic integrated circuit (PIC). This PIC consists of four high-speed silicon modulators, a polarization rotator, and a polarization beam combiner. A 112-Gb/s polarization-division-multiplexed (PDM) QPSK modulation is successfully demonstrated.
174 citations
TL;DR: By combining previously reported techniques, this work can achieve complete amplitude, phase and polarization control for the diffracted light that allows the creation of arbitrary diffractive optical elements including polarization control.
Abstract: We present a method to generate complete arbitrary spatially variant polarization modulation of a light beam by means of a parallel aligned nematic liquid crystal spatial light modulator (SLM). We first analyze the polarization modulation properties in a transmission mode. We encode diffraction gratings onto the SLM and show how to achieve partial polarization control of the zero order transmitted light. We then extend the technique to a double modulation scheme, which is implemented using a single SLM divided in two areas in a reflective configuration. The polarization states of the transmitted beam from the first pass through the first area are rotated using two passes through a quarter wave plate. The beam then passes through the second area of the SLM where additional polarization information can be encoded. By combining previously reported techniques, we can achieve complete amplitude, phase and polarization control for the diffracted light that allows the creation of arbitrary diffractive optical elements including polarization control. Theoretical analysis based on the Jones matrix formalism, as well as excellent experimental results are presented.
168 citations
TL;DR: Stressing bars are shown that offer tunable birefringence in the range from ~0 up to 4.35 × 10(-4), possibly enabling great flexibility in designing polarization dependent devices, as well as making polarization independent devices.
Abstract: Femtosecond laser exposure produces form and stress birefringence in glasses, mainly controlled by laser polarization and pulse energy, which leads to challenges in certain applications where polarization mode dispersion or birefringence splitting is critical for the desired responses from optical devices. In this paper, parallel laser modification tracks with different geometries were applied to preferentially stress the laser-written waveguides and explore the possibility of tuning the waveguide birefringence in devices fabricated in bulk fused silica glass. Polarization splitting in Bragg grating waveguides showed the laser modification tracks to controllably add or subtract stress to the pre-existing waveguide birefringence, demonstrating independence from the nanograting induced form birefringence and the contributions from material stress. Stressing bars are shown that offer tunable birefringence in the range from ∼0 up to 4.35 × 10−4, possibly enabling great flexibility in designing polarization dependent devices, as well as making polarization independent devices.
105 citations
TL;DR: In this article, the authors demonstrate the full control of polarization dependent light paths through a highly scattering medium by only shaping the incoming wavefront, which is independent of the incident beam's polarization and has no spatial restrictions.
Abstract: Current non-invasive imaging and manipulation of biological systems heavily rely on using light as the probing tool. However, light propagation through highly turbid media such as biological tissue undergo multiple light scattering which results in significant scrambling of light paths and polarization information. Here we demonstrate the full control of polarization dependent light paths through a highly scattering medium by only shaping the incoming wavefront. The resulting polarized state is independent of the incident beam’s polarization and has no spatial restrictions. We also show that a turbid medium can be used as a dynamic wave plate by controlling the phase of combined orthogonal polarization states. This approach may find direct applications in efficient energy transfer for photothermal therapy and the transfer of angular momentum in optical manipulation of biological systems.
103 citations
TL;DR: In this paper, a double-ring-chain metamaterial was proposed to enable both passive and active polarization conversion of terahertz radiation using planar metammaterials.
Abstract: We present a double-ring-chain metamaterial that enables efficient polarization conversion of terahertz waves. The experimental results and numerical simulations reveal that the linear-to-linear polarization rotation and linear-to-elliptic polarization transformation are simply accomplished by altering the dimensional parameters of the metamaterial unit cells. The polarization state conversion is found to be critically related to the resonant properties of the long bars and the rings in the unit geometries and is well described by the Jones matrix. This approach promises both passive and active polarization conversion of terahertz radiation using planar metamaterials.
101 citations
Journal Article•
TL;DR: Enhanced tissue discrimination as well as quantitative measurements of sample properties was demonstrated using the additional contrast and information contained in the PS-OCT images.
Abstract: Polarization sensitive optical coherence tomography (PS-OCT) is a functional imaging method that provides additional contrast using the light polarizing properties of a sample. This manuscript describes PS-OCT based on ultrahigh speed swept source / Fourier domain OCT operating at 1050nm at 100kHz axial scan rates using single mode fiber optics and a multiplexing approach. Unlike previously reported PS-OCT multiplexing schemes, the method uses a passive polarization delay unit and does not require active polarization modulating devices. This advance decreases system cost and avoids complex synchronization requirements. The polarization delay unit was implemented in the sample beam path in order to simultaneously illuminate the sample with two different polarization states. The orthogonal polarization components for the depth-multiplexed signals from the two input states were detected using dual balanced detection. PS-OCT images were computed using Jones calculus. 3D PS-OCT imaging was performed in the human and rat retina. In addition to standard OCT images, PS-OCT images were generated using contrast form birefringence and depolarization. Enhanced tissue discrimination as well as quantitative measurements of sample properties was demonstrated using the additional contrast and information contained in the PS-OCT images.
98 citations
TL;DR: It is shown that the polarization state of coherent light propagating through an optically thick multiple scattering medium can be controlled by wavefront shaping, that is, by controlling only the spatial phase of the incoming field with a spatial light modulator.
Abstract: We show that the polarization state of coherent light propagating through an optically thick multiple scattering medium can be controlled by wavefront shaping, that is, by controlling only the spatial phase of the incoming field with a spatial light modulator. Any polarization state of light at any spatial position behind the scattering medium can be attained with this technique. Thus, transforming the random medium to an arbitrary optical polarization component becomes possible.
89 citations
TL;DR: It is shown that, in order to attain complete polarization control across a beam, two spatially resolved variable retardations need to be introduced to the light beam.
Abstract: We show that, in order to attain complete polarization control across a beam, two spatially resolved variable retardations need to be introduced to the light beam. The orientation of the fast axes of the retarders must be linearly independent on the Poincare sphere if a fixed starting polarization state is used, and one of the retardations requires a range of 2π. We also present an experimental system capable of implementing this concept using two passes on spatial light modulators (SLMs). A third SLM pass can be added to control the absolute phase of the beam. Control of the spatial polarization and phase distribution of a beam has applications in high-NA microscopy, where these properties can be used to shape the focal field in three dimensions. We present some examples of such fields, both theoretically calculated using McCutchen’s method and experimentally observed.
85 citations
TL;DR: High precision measurements of polarization rotations in the frequency range from 0.1 to 2.5 THz using a polarization modulation technique are presented, showing its ability to fully characterize elliptical polarizations.
Abstract: We present high precision measurements of polarization rotations in the frequency range from 0.1 to 2.5 THz using a polarization modulation technique. A motorized stage rotates a polarizer at ~80 Hz, and the resulting modulation of the polarization is measured by a lock-in technique. We achieve an accuracy of 0.05° (900 {\mu}rad) and a precision of 0.02° (350 {\mu}rad) for small rotation angles. A detailed mathematical description of the technique is presented, showing its ability to fully characterize elliptical polarizations from 0.1 to 2.5 THz.
84 citations
TL;DR: In this article, the authors demonstrate a polarization rotator fabricated using a 4 etch-step complementary metal-oxide-semiconductor (CMOS)-compatible process including layer depositions on a silicon-on-insulator wafer.
Abstract: We demonstrate a polarization rotator fabricated using a 4 etch-step complementary metal-oxide-semiconductor (CMOS)-compatible process including layer depositions on a silicon-on-insulator wafer. The measured polarization rotation efficiency is over a wavelength range of 80 nm. A robustness investigation shows that the design is compatible with CMOS fabrication capabilities.
TL;DR: A novel ultracompact (5 μm) hybrid plasmonic polarization rotator operating at telecommunication wavelength for integrated silicon photonic circuits with low total insertion losses is proposed.
Abstract: We propose a novel ultracompact (5 μm) hybrid plasmonic polarization rotator operating at telecommunication wavelength for integrated silicon photonic circuits. The polarization mode of a silicon waveguide is rotated with >14 dB polarization extinction ratio and low total insertion losses of 2.1 dB.
TL;DR: Test results of a VPM at wavelengths of 350 μm and 3 mm are reported and electromagnetic simulations of wire grid polarizers were performed and are summarized using a simple circuit model that incorporates the loss and polarization properties of the device.
Abstract: We investigate the polarization modulation properties of a variable-delay polarization modulator (VPM). The VPM modulates polarization via a variable separation between a polarizing grid and a parallel mirror. We find that in the limit where the wavelength is much larger than the diameter of the metal wires that comprise the grid, the phase delay derived from the geometric separation between the mirror and the grid is sufficient to characterize the device. However, outside of this range, additional parameters describing the polarizing grid geometry must be included to fully characterize the modulator response. In this paper, we report test results of a VPM at wavelengths of 350 μm and 3 mm. Electromagnetic simulations of wire grid polarizers were performed and are summarized using a simple circuit model that incorporates the loss and polarization properties of the device.
TL;DR: In this paper, a multilayer structure consisting of an alternating sequence of chiral-metamaterial- and dielectric- plates was proposed for the terahertz frequency regime.
Abstract: The lack of wave-plates for the terahertz region opens the way for novel components/devices enabling polarization control at these frequencies. With the aid of chiral metamaterials | a new class of metamaterials | novel possibilities for the fabrication of multilayer structures for the realization of polarization rotators emerge. In this study, we present design and analysis of a polarization rotator for the terahertz frequency regime based on a multilayer structure consisting of an alternating sequence of chiral-metamaterial- and dielectric- plates. The combination of chiral constituents with dielectrics permits optimization of the spectral-fllter and polarization-rotation features. We can generate either polarization-rotation combs or narrow rotation bands with very good and broad sideband suppression, of interest for example for data transmission or sensing purposes.
TL;DR: It is found that the ferroelectric polarization of BiFeO3 films down to 3.6 nm decays strongly below a critical thickness of 5-7 nm predicted by continuous medium theory whereas the tetragonal distortion does not change, and this apparent contradiction is resolved using first-principles-based effective Hamiltonian calculations.
Abstract: We measure the ferroelectric polarization of BiFeO3 films down to 3.6 nm using low energy electron and photoelectron emission microscopy. The measured polarization decays strongly below a critical thickness of 5-7 nm predicted by continuous medium theory whereas the tetragonal distortion does not change. We resolve this apparent contradiction using first-principles-based effective Hamiltonian calculations. In ultrathin films, the energetics of near open circuit electrical boundary conditions, i.e., an unscreened depolarizing field, drive the system through a phase transition from single out-of-plane polarization to nanoscale stripe domains. It gives rise to an average polarization close to zero as measured by the electron microscopy while maintaining the relatively large tetragonal distortion imposed by the nonzero polarization state of each individual domain.
TL;DR: In this paper, a low-loss polarization rotator based on mode evolution using horizontal slot waveguide was proposed, which allows monolithic integration with active drive electronics and other photonic components.
Abstract: We report an efficient and low-loss polarization rotator based on mode evolution using horizontal slot waveguide. The device is fabricated using complementary metal–oxide–semiconductor compatible processes, which allows monolithic integration with active drive electronics and other photonic components. A rotator fabricated with 100 μm transition length provides a high extinction ratio >14 dB for both transverse-magnetic (TM)-transverse-electric (TE) and TE-TM rotation. The excess loss of the device is <1 dB for both rotations as etching of the bottom Si waveguide is prevented. The device also exhibits a uniform rotation response over C+L band wavelength range of 1530-1600 nm.
Patent•
11 Jul 2012TL;DR: In this article, an out-coupling polarizing beam splitter (PBS) is used to pass the CGI light along a forward propagation path and redirect it along a reverse propagation path out of an eye-ward side of the eyepiece.
Abstract: An eyepiece for a head mounted display includes an illumination module, an end reflector, a viewing region, and a polarization rotator. The illumination module provides CGI light along a forward propagation path within the eyepiece. The end reflector is disposed at an opposite end of the eyepiece from the illumination module to reflect the CGI light back along a reverse propagation path within the eyepiece. The viewing is disposed between the illumination module and the end reflector and includes an out-coupling polarizing beam splitter (“PBS”). The out-coupling PBS passes the CGI light traveling along the forward propagation path and redirects the CGI light traveling along the reverse propagation path out of an eye-ward side of the eyepiece. The polarization rotator is disposed in the forward and reverse propagation paths between the out-coupling PBS and the end reflector.
TL;DR: In this article, a polarization rotator in silicon-on-insulator technology based on breaking the symmetry of the waveguide cross section is reported, which is designed to be integrated with standard grating couplers without the need for extra fabrication steps.
Abstract: A polarization rotator in silicon-on-insulator technology based on breaking the symmetry of the waveguide cross section is reported. The 25- μm-long device is designed to be integrated with standard grating couplers without the need for extra fabrication steps. Hence, fabrication is carried out by a 2-etch-step complementary metal-oxide-semiconductor compatible process using 193-nm deep ultraviolet lithography. A polarization conversion efficiency of more than -0.85 & dB with insertion losses ranging from -1 to -2.5 & dB over a wavelength range of 30 nm is demonstrated.
TL;DR: A calibration technique allowing quantitative measurement of polarization parameters, such as the degree of polarization (DOP), degree of linear polarization, degree of circular polarization, as well as anisotropy from the acquired Stokes parameters is implemented.
Abstract: We developed a four-channel photon counting based Stokes-polarimeter for spatial characterization of polarization effects in second harmonic generation (SHG). We have implemented a calibration technique allowing quantitative measurement of polarization parameters, such as the degree of polarization (DOP), degree of linear polarization (DOLP), degree of circular polarization (DOCP), as well as anisotropy from the acquired Stokes parameters. The technique is used as contrast mechanism to characterize the polarization properties from two potassium dihydrogen phosphate (KDP) micro-crystals and collagen type-I in SHG microscopy.
TL;DR: For the high-energy end of the bremsstrahlung continuum the experimental results for both observables show a high on the initial electron spin polarization and prove that the polarization orientation is virtually independent of the photon energy.
Abstract: We report on a study of the polarization transfer between transversely polarized incident electrons and the emitted x rays for electron-atom bremsstrahlung. By means of Compton polarimetry we performed for the first time an energy-differential measurement of the complete properties of bremsstrahlung emission related to linear polarization, i.e., the degree of linear polarization as well as the orientation of the polarization axis. For the high-energy end of the bremsstrahlung continuum the experimental results for both observables show a high sensitivity on the initial electron spin polarization and prove that the polarization orientation is virtually independent of the photon energy.
TL;DR: In this article, the birefringence of photonic crystal fibers (PM-PCFs) under thermal effect is investigated and the experimental results are in agreement with theoretical calculation, and show that the relative temperature dependent birerringence coefficient of the PM-PCF, dΔ n /d T /Δn, is 2.93×10 −5 /°C, which is typically ∼35 times less than that of conventional panda fibers.
Abstract: In this paper, we investigate the birefringence of polarization maintaining photonic crystal fibers (PM-PCFs) under thermal effect. Modeling and simulation of PM-PCFs under thermal effect are conducted. Birefringence in a PM-PCF as a function of the temperature is measured experimentally. The experimental results are in agreement with theoretical calculation, and show that the relative temperature dependent birefringence coefficient of the PM-PCF, dΔ n /d T /Δ n , is 2.93×10 −5 /°C, which is typically ∼35 times less than that of conventional panda fibers. The insensitivity of polarization properties in PM-PCFs to temperature is demonstrated. These findings have important benefits in fiber optic systems and sensors, especially in fiber optic gyroscopes (FOG) where it translates into a lower polarization error and thus a higher measurement precision.
TL;DR: Using azimuthal polarization, it is shown that an amplitude-phase filter allows generation of a subdiffractive dark spot in a prescribed finite area.
Abstract: We compare generation of a dark spot using focusing of beams with azimuthal polarizion, radial polarization with a vortex, and a circular polarization with either a first or second order vortex. By optimization of the amplitude-phase pupil, it is ascertained that azimuthal polarization is the most suitable one to obtain the diffraction bounded dark spot per se whose scalar approximation limit has FWHM=0.29λ. Consequently, for dark spot generation, this polarization plays the role of the radial polarization in creation of the diffraction-limited bright spot. Using azimuthal polarization, it is shown that an amplitude-phase filter allows generation of a subdiffractive dark spot in a prescribed finite area.
TL;DR: A class of optical fields whose polarization content at any transverse plane spans a disk-like region within the Poincaré sphere, and when examined through a paraxial focal region, the disk rotates under propagation, spanning all possible states of polarization.
Abstract: Optical fields whose coherence and/or polarization properties appear to change under propagation have intrigued researchers for many years. We describe and experimentally demonstrate a class of optical fields whose polarization content at any transverse plane spans a disk-like region within the Poincare sphere. When examined through a paraxial focal region, the disk rotates under propagation, spanning all possible states of polarization. We map the change in Stokes parameters through focus for each case, comparing experiment with the theoretical predictions.
TL;DR: A polarization rotator, suitable for integration in a polarization diversity optical receiver fabricated in InP technology, includes tapered input and output ports that provide very low insertion loss, significantly reducing complexity and cost.
Abstract: A polarization rotator, suitable for integration in a polarization diversity optical receiver fabricated in InP technology, is proposed. The device, based on a two steps waveguide rotator, includes tapered input and output ports that provide very low insertion loss (<0.04 dB). An extinction ratio of 40 dB at 1550 nm wavelength is calculated, comparable or even superior to other state of the art polarization converters. The main advantage of the proposed design is the capability of implementation using a standard fabrication process with only two dry etch steps, significantly reducing complexity and cost.
TL;DR: A mode-evolution-based polarization rotator-splitter built on InP substrate is proposed by combining a mode converter and an adiabatic asymmetric Y-coupler, which effectively converts the fundamental TM mode into the second order TE mode without changing the polarization of the fundamental TE mode.
Abstract: A mode-evolution-based polarization rotator-splitter built on InP substrate is proposed by combining a mode converter and an adiabatic asymmetric Y-coupler. The mode converter, consisting of a bi-level taper and a width taper, effectively converts the fundamental TM mode into the second order TE mode without changing the polarization of the fundamental TE mode. The following adiabatic asymmetric Y-coupler splits the fundamental and the second order TE modes and also converts the second order TE mode into the fundamental TE mode. A shallow etched structure is proposed for the width taper to enhance the polarization conversion efficiency. The device has a total length of 1350 µm, a polarization extinction ratio over 25 dB and an insertion loss below 0.5 dB both for TE and TM modes, over the wavelength range from 1528 to 1612 nm covering all C + L band. Because the device is designed based on mode evolution principle, it has a large fabrication tolerance. The insertion loss remains below 1 dB and the polarization extinction ratio remains over 17 dB with respect to a width variation of +/− 0.12 µm at the wavelength of 1570 nm, or +/− 0.08 µm over the entire C + L band.
TL;DR: In this article, the amplitude of variability of the polarized flux is comparable to that of the total U-band flux with a lag of 8 + − 3 days, and it is assumed that the polarization arises from electron scattering in a flattened region within the low-ionization component of the broad line region.
Abstract: Observations of the optical polarization of NGC 4151 in 1997-2003 show variations of an order of magnitude in the polarized flux while the polarization position angle remains constant. The amplitude of variability of the polarized flux is comparable to the amplitude of variability of the total U-band flux, except that the polarized flux follows the total flux with a lag of 8 {+-} 3 days. The time lag and the constancy of the position angle strongly favor a scattering origin for the variable polarization rather than a non-thermal synchrotron origin. The orientation of the position angle of the polarized flux (parallel to the radio axis) and the size of the lag imply that the polarization arises from electron scattering in a flattened region within the low-ionization component of the broad-line region. Polarization from dust scattering in the equatorial torus is ruled out as the source of the lag in polarized flux because it would produce a larger lag and, unless the half-opening angle of the torus is >53 Degree-Sign , the polarization would be perpendicular to the radio axis. We note a long-term change in the percentage of polarization at similar total flux levels, and this could be due eithermore » to changing non-axisymmetry in the optical continuum emission or a change in the number of scatterers on a timescale of years.« less
TL;DR: A new coupled mode equation is built to describe the pure twist polarization mode coupling, in which both the normal strain induced by strain-applied parts and the tangential straininduced by twisting are taken into consideration and expressed in a unified coordinate.
Abstract: Spectral characteristics of orthogonal polarization mode coupling for pure twisted polarization maintaining fiber Bragg gratings (PM-FBG) are proposed and analyzed experimentally and theoretically. Different from the polarization mode coupling in PM-FBG due to side pressure, a resonant peak at the middle of two orthogonal polarization modes is found when the PM-FBG is twisted purely which is attributed to the cross coupling of polarization modes. Its intensity increases with the twisting rate. A new coupled mode equation is built to describe the pure twist polarization mode coupling, in which both the normal strain induced by strain-applied parts and the tangential strain induced by twisting are taken into consideration and expressed in a unified coordinate. The novel phenomenon and its explanation are believed to be helpful for PM-FBG applications in fiber sensor and laser technologies.
TL;DR: In this article, the polarization splitting wavelength-selective characteristics of Au-filled high-birefringence photonic crystal fiber (HB-PCF) based on the finite element method is investigated.
Abstract: Polarization splitting wavelength-selective characteristics of Au-filled high-birefringence photonic crystal fiber (HB-PCF) based on the finite element method is investigated. Numerical results show that the polarization splitting effect can be observed in metal-filled HB-PCF. The resonances points and strength in two polarizations can be adjusted by changing the fiber birefringence, the pitch between the adjacent air holes and the size of the metal wires. Finally, two kinds of Au-filled HB-PCFs with completely polarization splitting and filtering characteristics in communication wavelength are designed. Results show that this polarization splitting effect in metal-filled HB-PCF is very useful for further studies in polarization-dependent wavelength-selective applications and other fiber-based plasmonic devices.
TL;DR: In this article, a planar chiral metamaterial (CMM) was proposed to realize the intriguing phenomenon of 90°polarization rotation to the electromagnetic wave incidence with a linear polarization.
Abstract: We present a novel planar chiral metamaterial (CMM) that can realize the intriguing phenomenon of 90°-polarization rotation to the electromagnetic wave incidence with a linear polarization. This CMM consists of fourfold-symmetrically conjugated metallic pairs, which exhibits a circular dichroism and a giant optical activity. The fascinating 90°-polarization rotation of electromagnetic wave for a wide angle of incidence is demonstrated by both simulations and experiments. To be specific, the rotation angle per wavelength in our design is as large as 3400°/λ, implying that the chirality is significantly stronger than any other planar CMMs reported previously. Due to the giant chirality, the negative refractive index is achieved for circularly polarized waves.
TL;DR: Experimental results reveal that high purely polarized (polarization purity of 95% or better) azimuthal and radial beams can be generated.
Abstract: A new architecture for generating pure azimuthally and radially polarized beams is presented. It involves coherent polarization beam combination of two orthogonally polarized LP11 fiber modes. Experimental results reveal that high purely polarized (polarization purity of 95% or better) azimuthal and radial beams can be generated.