Evolution Of Polarization State Research Articles

Manipulation of polarization conversion and dual foci in a twisted caustic vector optical field in free space

Manipulation of polarization states in a complex structured optical field during propagation has become an important topic due to its fundamental interest and potential applications. This work demonstrates the effect of the caustic and twisting phases on the polarization states of a vector beam experimentally and theoretically. The novel properties of polarization evolution, especially the conversions of different states of polarization (SoPs) in a twisted caustic vector beam, occur during propagation in free space because of the modulation of twisting and caustic phases. The orthogonal polarization components tend to appear on the beam centers of two foci, and the two focal distances are closely related to the caustic and twisting phases. The twisting and caustic phases can manipulate the conversions between linear and circular polarization components that occur during propagation. These results provide a new approach to more complex manipulations of a structured optical field, especially in tailoring the evolution of polarization states and two foci. They may find potential applications in the corresponding field.

Geometric phase and photonic spin Hall effect in thin films with architected columnar morphology

We have detected spin-dependent splitting of light, the signature of the photonic spin Hall effect (PSHE), via quantum weak measurements on two types of thin films with architected columnar morphology. Specifically, we fabricated columnar thin films comprising parallel tilted nanocolumns and chiral sculptured thin films comprising parallel upright nanohelices by resistively heating zinc selenide (ZnSe) in a low-pressure chamber and collecting the collimated vapor flux of ZnSe on planar substrates with dynamically varying orientation. The architected columnar morphology creates a spin-dependent geometric Pancharatnam–Berry (PB) phase corresponding to the evolution of polarization states on the Poincaré sphere. Morphology-controlled anisotropy and spatial inhomogeneity result in the depolarization and optical rotation of incident plane-polarized light, and intrinsic spin-precession coupling with the propagation vector, contributing to the efficient generation and two-dimensional manipulation of both in-plane and out-of-plane spin splitting and steering the PB phase in the propagation process. The first experimental observations of widely tailorable PSHE and PB phase in thin films with architected columnar morphology may lead to new applications ranging from spin-controlled nanophotonics to optoelectronic devices for quantum information processing and optical communication.

Polarization state evolution of a twisted vector optical field in a strongly nonlocal nonlinear medium.

The evolution of the state of polarization (SoP) in a twisted vector optical field (TVOF) with an astigmatic phase in a strongly nonlocal nonlinear medium (SNNM) is investigated. The effect of an astigmatic phase on the propagation dynamics of the twisted scalar optical field (TSOF) and TVOF during propagation in the SNNM leads to reciprocally periodical evolutions of stretch and shrink, accompanied by the reciprocal transformation of the beam shape between an initial circle shape and threadiness distribution. The TSOF and TVOF rotate along the propagation axis if the beams are anisotropic. In particular, the reciprocal conversions between the linear and circular polarizations occur in the TVOF during propagation, which are strongly related to the initial powers, twisting strength coefficients, and initial beam reshapes. The numerical results confirm the analytical predictions by the moment method for the dynamics of the TSOF and TVOF during propagation in a SNNM. The underlying physics for the polarization evolution of a TVOF in a SNNM are discussed in detail.

Effect of Twisting Phases on the Polarization Dynamics of a Vector Optical Field

The effect of twisting phases on the polarization dynamics of a vector vortex beam with a spatially variant state of polarization (SoP) is investigated theoretically and experimentally. The twisted vector vortex optical field with the cross-phase modulation is experimentally generated and observed. The presence of the twisting phases on the vector optical field results in novel propagation dynamics and the evolution of polarization states. The optical field performs the process of compressing and stretching the orthogonal polarization components and the linear-circular polarization conversions during propagation. Different from the scalar twisted beams, the orthogonal polarization components of twisted vector beams can be compressed along the same azimuthal angle or the orthogonal azimuthal angles, depending on the signs of the twist intensity coefficients. For an anisotropic twisted optical field, the SoP and the optical field rotate, and the rotation behaviors are sensitively dependent on the twisting coefficients. Furthermore, the two vortex topological charges embedded within the orthogonal polarization component of a twisted vector vortex beam can be simultaneously identified by looking at the interference fringes of the twisting phases. This work reveals that a vector vortex beam and its SoP can be dynamically manipulated by twisting phases.

Creating Longitudinally Varying Vector Vortex Beams with an All‐Dielectric Metasurface

AbstractVector vortex beams have attracted considerable research attention owing to their unique optical properties, and have been explored in vortex filtering, photon entanglement, and the photonic spin hall effect. In this work, a universal all‐dielectric metasurface platform is proposed that can generate longitudinally varying vector vortex beams in the terahertz band. As a proof‐of‐concept demonstration, a series of metasurface examples generating evolution of topological charges and vector polarization states of generated vector vortex beams are characterized. The experimental results agree well with the simulations, fully verifying the feasibility of the proposed scheme. The proposed metasurface strategy may find applications ranging from optical traps to polarization optics.

Identification of Railway Power Supply Voltage Sag Source Using Optical Fiber Voltage Sensor

With the construction of the smart grid and the continuous improvement of voltage levels, the traditional voltage sensor can no longer meet the development needs of the modern power system. There is an urgent need for a new high-quality voltage sensor to replace it. Aiming at the problems of complex structure, difficult adjustment, poor temperature stability, large optical power loss and inconvenient voltage introduction of the existing optical fiber voltage sensor, an optical fiber voltage sensor based on full polarization state detection without polarizer and analyzer is proposed. The sensor only contains three main components: Grin Lens, BGO crystal and total reflection mirror. It has few devices, simple structure and easy alignment. Moreover, the polarization state evolution and high voltage on the transmission line of Pockels effect of BGO crystal are analyzed. The voltage sag simulation model of the electrified railway is established. The sample data of different disturbance sources are obtained with the assistance of the designed optical fiber voltage sensor. S-transformation and Radial Basis Function (RBF) neural networks are introduced and combined with the prototype of electrified railway power quality detection and analysis device to identify voltage sag sources. The designed optical fiber voltage sensor is suspended. There is no electrode or grounding on the sensor, which saves expensive insulators and increases the sensor’s measuring range. The sensor has a good linear relationship in the power frequency AC voltage range of 0~10 kV at room temperature. It is proved that the design is effective. The working condition analysis of the actual railway power supply reveals that it can detect the voltage sag amplitude and disturbance time, and identify the type of voltage sag disturbance source.

Spatial dynamics of light quasispin vector in an anisotropic medium with twisting

On the Poincar's sphere the spatial evolution of the light's polarization state has been studied quantitatively in the smoothly inhomogeneous anisotropic media with gyrotropy. The main features of the dependence on the sample?s thickness, the gyration vector and the azimuth of the polarization of the incident linearly polarized wave were revealed. An analytical solution of the system of coupled equations relative to Cartesian components of light's wave electric component obtained by transition to rotating coordinate system has been used for analysis. Keywords: Poincar' sphere, polarization evolution, medium with gyrotropy, rotating coordinate system.

Polarization sensitive optical coherence tomography with single input for imaging depth-resolved collagen organizations

Collagen organization plays an important role in maintaining structural integrity and determining tissue function. Polarization-sensitive optical coherence tomography (PSOCT) is a promising noninvasive three-dimensional imaging tool for mapping collagen organization in vivo. While PSOCT systems with multiple polarization inputs have demonstrated the ability to visualize depth-resolved collagen organization, systems, which use a single input polarization state have not yet demonstrated sufficient reconstruction quality. Herein we describe a PSOCT based polarization state transmission model that reveals the depth-dependent polarization state evolution of light backscattered within a birefringent sample. Based on this model, we propose a polarization state tracing method that relies on a discrete differential geometric analysis of the evolution of the polarization state in depth along the Poincare sphere for depth-resolved birefringent imaging using only one single input polarization state. We demonstrate the ability of this method to visualize depth-resolved myocardial architecture in both healthy and infarcted rodent hearts (ex vivo) and collagen structures responsible for skin tension lines at various anatomical locations on the face of a healthy human volunteer (in vivo).

Terahertz wavefront shaping with multi-channel polarization conversion based on all-dielectric metasurface

Polarization manipulation of electromagnetic wave or polarization multiplexed beam shaping based on metasurfaces has been reported in various frequency bands. However, it is difficult to shape the beam with multi-channel polarization conversion in a single metasurface. Here, we propose a new method for terahertz wavefront shaping with multi-channel polarization conversion via all-silicon metasurface, which is based on the linear shape birefringence effect in spatially interleaved anisotropic meta-atoms. By superimposing the eigen- and non-eigen-polarization responses of the two kinds of meta-atoms, we demonstrate the possibility for high-efficiency evolution of several typical polarization states with two independent channels for linearly polarized waves. The measured polarization conversion efficiency is higher than 70% in the range of 0.9–1.3 THz, with a peak value of 89.2% at 1.1 THz. In addition, when more other polarization states are incident, combined with the integration of sub-arrays, we can get more channels for both polarization conversion and beam shaping. Simulated and experimental results verify the feasibility of this method. The proposed method provides a new idea for the design of terahertz multi-functional metadevices.

Polarization evolution on the higher-order Poincaré sphere via photonic Dirac points

In this work, we report a general reflection model to describe the reflected behaviors of a Gaussian beam near photonic Dirac point at the optical interface. With spin polarized electromagnetic waves strikes near the single Dirac point on Dirac material interface, vortical phase distribution and spin inversion are demonstrated for reflected state, and we further develop a higher-order Poincar\'e sphere to describe the evolution of polarization states. It is possible to generate any desired Poincar\'e vortex beam on the sphere by modulating the incident polarization state of light. Moreover, we discuss the case of normal incidence around two adjacent Dirac points, reflection spectrum involves a couple of spin flip vortices corresponding to two points with the corresponding topological invariants, which are consistent with the Berry curvature and topological charge. These results can be extended to similar hyperbolic metamaterials with degenerate point, and inspire a different perspective for manipulating polarized vortex beam with photonic Dirac point.

Bessel-like beams with controllable rotating local linear polarization during propagation.

Bessel-like beams with controllable rotation of local linear polarization upon propagation are generated, which in fact achieve the evolution of polarization states along the equator of the Poincaré sphere during propagation. Based on the amplitude-phase joint modulation method, the rotation direction and rate of polarizations of the Bessel-like beam can be controlled easily by adjusting the radial indices and intensity ratio of two superposed beams. A rotation angle of $\sim$∼800 deg has been achieved after a propagation distance of 120 mm, corresponding to a rotation rate of $\sim$∼6.7 deg/mm, which is about three times higher than in previous works.

Three-dimensional polarization ray tracing in electro-optic crystals

Electro-optic crystals are extensively utilized to manipulate polarized light. In this paper, a general and accurate three-dimensional polarization ray tracing calculus for characterizing the evolution of polarization state in electro-optic crystals is reported for the first time. The analytical formulas of the parameters describing the propagation properties of the light passing through an electro-optical crystal with an arbitrary incident direction are derived. The partial interference between the divergent light beams is considered in the proposed calculus. Both experiments and calculations on an electro-optic modulator based on a lithium niobate crystal over the azimuth angle of 0∘-360°and the incidence angle of 0∘-3°are presented as an example. The experimental results show very good agreement with the theoretical results.

Approximate solutions of polarization state evolution in tokamak plasma polarimetry and their precision

Polarimetry measurement results are used in tokamak plasma equilibrium codes as a constraint, decreasing the measurement uncertainty in determination plasma current, safety factor and density profile. In numerical codes, instead of solving rigorous equation of polarimetric state evolution, approximate analytical expression could be used to increase computing efficiency. In this paper is analyzed the precision of three different models compared with exact solution of polarization state evolution equation. Calculations are made for circular plasma model, with plasma parameters representative for operating domain of tokamak device. The obtained results define the limits of applicability of the separate proposed approximated methods in equilibrium codes for plasma in configuration similar to considered in the paper.

Constrained polarization evolution simplifies depth-resolved retardation measurements with polarization-sensitive optical coherence tomography.

We observed that the polarization state of light after round-trip propagation through a birefringent medium frequently aligns with the employed input polarization state 'mirrored' by the horizontal plane of the Poincaré sphere. We explored the predisposition for this mirror state and evidence that it constrains the evolution of polarization states as a function of the round-trip depth into weakly scattering birefringent samples, as measured with polarization-sensitive optical coherence tomography (PS-OCT). Combined with spectral variations in the polarization state transmitted through system components, we demonstrate how this constraint enables measurement of depth-resolved birefringence using only a single input polarization state, which offers a critical simplification compared to conventional PS-OCT employing two input states.

Poincaré sphere-based technique for tuning flat-top fiber comb filter

We propose a universal method for designing flat-top passband and wavelength tuning of transmission spectrum of a fiber comb filter based on a polarization-diversified loop structure using Poincaré sphere representation. The proposed method gives a clear visualization of the evolution of polarization state through birefringent optical elements comprising the filter, and the design results are experimentally verified. Our method can also suggest which optical components are necessary for a specifically desired transmission spectrum of the comb filter.

QKD optical scheme calibration system

One-way quantum key distribution (QKD) optical schemes require active stabilization algorithms for continuous operation. To achieve this a mathematical model for a new optical scheme has been developed. The model uses Jones calculus to describe the polarization state evolution within the optical scheme. The developed algorithms have been successfully tested experimentally.

Electromagnetic wave polarization state evolution in weakly anisotropic and nonuniform media with dissipation

The change of the polarization state of electromagnetic beam propagating in weakly anisotropic and smoothly inhomogeneous media with dissipation is analysed. On the basis of a quasi-isotropic approximation, which provides the consequent asymptotic solution of Maxwell's equation, the differential equation for the evolution of four component Stokes vector is derived. Obtained equation generalizes previous results for the nonadsorbing media and is written in terms of the dielectric tensor of birefringent media with dissipation. The formalism is illustrated by an example of magnetised plasma with dissipation due to the electron collisions. Full Text: PDF ReferencesK.G.Budden, Radio Waves in the Ionosphere (Cambridge U. Press 1961).V.I.Ginzburg, Propagation of Electromagnetic Waves in Plasma (Gordon & Breach 1970).Yu.A.Kravtsov, ""Quasiisotropic" Approximation to Geometrical Optics", Sov. Phys. Dokl. 13, 1125 (1969).A.A. Fuki, Yu.A. Kravtsov, and O.N. Naida, Geometrical Optics of Weakly Anisotropic Media (Gordon & Breach, Lond., N.Y. 1997).Yu.A. Kravtsov and Yu.I. Orlov, Geometrical optics of inhomogeneous media (Springer Verlag, Berlin, Heidelberg 1990). CrossRef Yu.A. Kravtsov et al., "Waves in weakly anisotropic 3D inhomogeneous media: quasi-isotropic approximation of geometrical optics", Physics-Uspekhi 39, 129(1996). CrossRef F.De Marco, S.E.Segre, "The polarization of an e.m. wave propagating in a plasma with magnetic shear. The measurement of poloidal magnetic field in a Tokamak", Plasma Phys. 14, 245 (1972). DirectLink S.E.Segre, "A review of plasma polarimetry - theory and methods", Plasma Phys. Control. Fusion 41, R57 (1999). CrossRef M. Born and E. Wolf, Principles of Optics (Pergamon, Oxford 1980). CrossRef B.Bieg et al., "Quasi-Isotropic Approximation of Geometrical Optics Method as Adequate Electrodynamical Basis for Tokamak Plasma Polarimetry", Physics Procedia 62, 102 (2015). CrossRef B.Bieg et al., "Two approaches to plasma polarimetry: Angular variables technique and Stokes vector formalism", Nucl. Instr. Meth. Phys. Res. Sect. A 720, 157 (2013). CrossRef S.E.Segre, "New formalism for the analysis of polarization evolution for radiation in a weakly nonuniform, fully anisotropic medium: a magnetized plasma", J. Opt. Soc. Am. A 18, 2601 (2001). CrossRef

Polarization state evolution in spun birefringent optical fibers

The evolution of the polarization state (PS) of radiation propagating in spun or twisted birefringent optical fibers is considered for a wide range of fiber parameters, and presented in a descriptive way using the Poincaré sphere. The effects of the bandwidth and the polarization state of input radiation, of the external magnetic field, and of the fiber bending on the polarization state evolution have been described for the most practical cases. An explanation of how the helical structure of the built-in linear birefringence in spun fibers provides the existence of the helical elliptically-polarized eigenmodes has been given. In spun fibers with a relatively large spin rate, the PS evolution is shown to change its azimuthal direction.

Optimal polarization modulation for orthogonal two-axis Lloyd's mirror interference lithography.

Polarization control is of vital importance in two-axis Lloyd's mirror interference lithography to achieve the preferred interference fringes. In this work, we first establish a three-dimensional polarization ray-tracing model to trace the evolution of polarization states of incident beams through the corner-cube-like interferometer unit of an orthogonal two-axis Lloyd's mirror interferometer. With the established model, we then derive the optimal combination of initial polarization directions of the incident beams according to the orthogonality of polarization states and the contrast of interference fringes. The comparison between the simulated and experimental interference fringes obtained under different combinations of initial polarization states of incident beams verify the feasibility of the established model and the achieved optimal polarization modulation.

Acceleration toward polarization singularity inspired by relativistic E×B drift.

The relativistic trajectory of a charged particle driven by the Lorentz force is different from the classical one, by velocity-dependent relativistic acceleration term. Here we show that the evolution of optical polarization states near the polarization singularity can be described in analogy to the relativistic dynamics of charged particles. A phase transition in parity-time symmetric potentials is then interpreted in terms of the competition between electric and magnetic ‘pseudo’-fields applied to polarization states. Based on this Lorentz pseudo-force representation, we reveal that zero Lorentz pseudo-force is the origin of recently reported strong polarization convergence to the singular state at the exceptional point. We also demonstrate the deterministic design of achiral and directional eigenstates at the exceptional point, allowing an anomalous linear polarizer which operates orthogonal to forward and backward waves. Our results linking parity-time symmetry and relativistic electrodynamics show that previous PT-symmetric potentials for the polarization singularity with a chiral eigenstate are the subset of optical potentials for the E×B “polarization” drift.