Polarization Ellipse Research Articles

Improved temporal characteristics for post-compressed pulses via application-tailored nonlinear polarization ellipse rotation

Improved temporal characteristics for post-compressed pulses via application-tailored nonlinear polarization ellipse rotation

Controllable temporal twisting polarization within an ultrafast laser pulse.

We propose a method for controlling the time-varying polarization of optical pulses by introducing a quarter-wave plate into a 4-f pulse shaper and using a spatial light modulator to impose a group delay. This setup enables the polarization state of the incident pulse to vary over time. Specifically, for linearly chirped incident pulses, the polarization ellipse twists uniformly over time, while its ellipticity changes monotonically. As the group delay increases, the pulse intensity gradually splits in the time domain, transitioning from a single pulse with uniformly twisting polarization to two circularly polarized pulses with opposite chirality. We provide a detailed and comprehensive explanation of this modulation process using analytical expressions.

Single-shot polarization detection with a highly scattering system

Polarization detection plays a significant role in optics. However, the current detection methods usually involve mechanically rotating components, multiple measurement steps, complicated optical design, and precise microfabrication process. To address this issue, we propose a single-shot method to detect the polarization state of light based on a highly scattering system, which is constituted by a spatial light modulator and a highly scattering medium. When the incident light beam shaped by a superimposed wavefront is incident on a highly scattering medium, the foci represented the six components at horizontal, vertical, diagonal, antidiagonal, right circularly polarized, and left circularly polarized directions will appear behind the highly scattering medium simultaneously. By measuring the intensities of these six foci, all the Stokes parameters can be extracted. Taking advantage of the measured Stokes parameters, the orientation angle of major axis, the ellipticity, and the handedness of the polarization ellipse of incident light beam can be determined. Various light beams with different polarization states are detected to demonstrate the viability of the method. The experimental results and theoretical values are in a good agreement. Compared to the existing methods, this approach is fast, free of complicated fabrication, and independent of mechanical movement. The proposed method is expected to promote the development of real-time and broadband polarimetry.

Peculiarities of polarised light scattering in nematic liquid crystals with large-scale director perturbations

ABSTRACT We examine light scattering in a birefringent material, namely uniaxial nematic liquid crystal possessing macroscopic orientation perturbations (variations of director in planar alignment). Our theoretical analysis and direct experiments proved that the polarisation state of the scattered speckle-field is uniform and elliptical (in a common case). The polarisation ellipse azimuth of scattered waves is mirror reflected to one of the directly transmitted waves relative to the optical axis.

Polarization Möbius strip at the tight focus of a generalized Poincaré beam

Based on the Richards-Wolf formalism, we investigate tight focusing of a generalized Poincaré beam. Analytical expressions are derived for all components of the electric field strength vector in the focal plane. For superposition of a right-handed circularly polarized plane wave with a left-handed circularly polarized optical vortex with topological charge –1, we obtain expressions for the intensity distribution and the longitudinal component of the spin angular momentum vector at the tight focus. We demonstrate both theoretically and numerically that the initial beam has topological charge –1/2 and, in the center of the focal plane, there is a C-point (a point with circular polarization which makes a C-line along the optical axis) with the singularity index of –1/2 (star), whereas the vector of major axis of the polarization ellipse makes along a certain-radius circle around the optical axis a single-side polarization Möbius stripe of the order –3/2, which has three half-turnovers and one stitching, where two opposite major axis vectors of the polarization ellipse meet.

Terahertz polarization sensing for influenza A virus based on plasmonic metasurface

Terahertz metasurface sensors attract extensive attention for excellent characterisics. However, most existing sensing schemes overlooked the polarization state of electromagnetic waves. Here, we propose a plasmonic metasurface sensor based on the elliptical polarization state of reflected EM wave, which can be used for the sensing of influenza A virus. The sensor achieves the conversion from linear polarization to circular polarization within 1–3 THz. By analysing the electromagnetic field distributions of the resonances at 1.43 THz and 2.16 THz, it can be concluded that the polarization conversion originates from the magnetic dipole. Besides, the sensor can characterize the changes in the complex refractive index of the test sample based on the elliptical polarization state of the reflected wave. The electromagnetic response of the metasurface sensor shows an excellent linear relationship between the rotating direction angle of polarization ellipse and the extinction coefficient (k) of the complex RI of the analyte. Furthermore, we also demonstrate the feasibility of detecting three subtypes of Influenza A viruses (H1N1, H5N2, and H9N2) at 1.39 THz though the elliptical polarization state. This sensing approach does not rely on high-precision broadband scanning, providing an alternative perspective for THz biosensing.

Highly sensitive terahertz polarization biosensor utilizing chiral metasurface

In order to achieve a highly sensitive biosensor with a simple structure, we propose a chiral metasurface polarization sensor. Using immunological surface plasmon resonance (SPR) detection, the antigen or antibody is fixed as a probe on the SPR metasurface to detect the corresponding antibody or antigen. Through the change of the refractive index of the analyte on the surface facial mask, the terahertz signal changes, and finally the sensing detection of avian influenza virus can be achieved. The designed metasurface adopts a hollow split sector chiral structure to generate chiral surface current, which can convert linearly polarized incident waves as elliptical polarized waves. The structure achieves the high sensitivity of 401 deg/RIU at frequency of 0.8 THz, and the avian influenza virus (H1N1, H5N2 and H9N2) with the same real part of the refractive index can also be distinguished. Influenza viruses belong to the family Orthomyxoviridae of RNA viruses, divided into three types: A, B, and C. In this article, avian influenza viruses belong to type A influenza viruses. It can clearly identify different Avian Influenza Viruses by the two polarization characteristic parameters of the reflection spectrum PEA (Polarization Ellipse Angle) and PRA (Polarization Rotation Angle). This method has a significant application prospect in the fields of biomedicine and food industries.

Transverse Spin Hall Effect and Twisted Polarization Ribbons at the Sharp Focus

Transverse Spin Hall Effect and Twisted Polarization Ribbons at the Sharp Focus

Generation of High‐Purity Full Poincaré Beam Arrays via Metasurface Integrated Degenerate Cavity

AbstractRecently, full Poincaré beams (FPBs) with spatially variant polarization states spanning the entire surface of the Poincaré sphere have attracted considerable interests. Expanding the FPBs into an array way has the promising applications from multiparticle manipulation to optical communication. However, how to efficiently generate a high‐purity FPB array with intracavity method remains elusive. Here, a metasurface‐integrated degenerate cavity laser is proposed for efficient generation of 10 × 10 FPB array, where a pair of metasurfaces are adopted to independently modulate the circular polarization state while compensating the mode discrepancies within the cavity. Such a design strategy enables a self‐reproducing intracavity optical field, concurrently ensuring the stabilization of intracavity oscillation. It is numerically demonstrated that the purity of orbital angular momentum (OAM) in the first‐order FPB array can approach to 92.89%, with a root‐mean‐square error (RMSE) of polarization ellipse parameters below 8.17%. This work provides a compact and efficient design platform for the generation of a variety of vector beam arrays and may find promising applications in free space communication and multiple particle manipulation.

Determining triple half-twist of optical Möbius strips in electromagnetic fields with a non-planar structure.

Polarization ellipses in a nonparaxial field form twisted strips when traced along closed contours around a circular polarization singularity line. We found an analytical expression for the twist number of the strip when the contour is coplanar with the polarization ellipse in its center. Necessary and sufficient conditions for strips having one or three half-twists are found. A set of five parameters of electromagnetic field at the polarization singularity point is found which definitely determines the value of the twist number of the strip.

Generation of pure transverse spin and nontrivial polarization structures of beams by dielectric metasurface

Transverse spin, a spin component with unique characteristics, provides a new dimension for plenty of applications, such as optical trapping, imaging, and communication. Here, we analyze the pure transverse spin in the Bessel beam, which is solely present in the azimuthal direction. Based on a single layer dielectric metasurface, we efficiently generate Bessel beams with pure transverse spin in a compact optical system. As designed, the transverse spin is flexibly tunable by converting the polarization of the incident light. Furthermore, in the scattered Bessel beam, the local electromagnetic field oscillates around the transverse axis, which is perpendicular to the beam propagation. At certain positions, the local polarization ellipse degenerates into a perfect circle, resulting in a ring-periodic distribution of circularly polarized points (C points) in the beam. This suggests that the local polarization demonstrates a nontrivial periodic structure. This work deepens our understanding of spin-related physics and opens a new avenue for the study and application of transverse spins in ultracompact, flat, multifunctional nanophotonic platforms.

Polarization Ellipse Strips in Nonparaxial Optical Fields (Brief Review)

Polarization Ellipse Strips in Nonparaxial Optical Fields (Brief Review)

Broadband-tunable quarter wave plates based on paired metal nanowire grids

Ultrathin wave plates based on metallic and dielectric metasurfaces have attracted much attention for independently controlling the phase, amplitude, and polarization of incident light. However, the issues of narrow bandwidth and low polarization conversion need to be improved for their optical applications. In this study, we show that an array of paired metal nanowire grids (PMNG) covered with a dielectric layer controls the polarization state in a broadband of visible to mid-infrared wavelengths. By analyzing the phase difference and amplitude ratio of orthogonal electric-field components passing through the SiO2-covered PMNGs, it is observed that the wavelengths operating as a circular polarizer appear regularly in the range from 450 nm to 4.0 μm with a stable phase difference of π/2. Also, the array of PMNG continuously converts linear polarization into circular or elliptical polarization by rotating the polarization angle of the incident light. Then, we demonstrate experimentally accessible polarization control by investigating the change in polarization ellipse between input and output light for this PMNG structure. Moreover, the PMNG can play an effective role as a wire grid polarizer in the IR region. Therefore, the suggested PMNG platform can be variously applied to emerging fields requiring ultrathin, multifunctional, and high-performance planar polarization components.

Full-Stokes metasurface polarimetry requiring only a single measurement

Polarization is crucial in various fields such as imaging, sensing, and substance detection. A compact, fast, and accurate polarization detection device is vital for these applications. Herein, we demonstrate a multifocus metalens for terahertz polarization detection that requires only a single measurement to obtain complete polarization parameters and reconstruct the polarization state of the incident field. The individual subarrays of this metalens convert each of the six polarized components into the same polarization, which in turn links the Stokes parameters to these six foci. The incident linear polarizations and elliptical polarizations are characterized by Stokes parameters and polarization ellipses. Simulations and experimental results show that the scheme can accurately detect the incident polarization with a single measurement. The proposed metasurface polarimetry may find applications in the fields of real-time terahertz detection and integrated optics.

Polarization singularity index determination using wedge plate lateral shear interferometry

Polarization singularity is a point in an inhomogeneous polarization distribution at which the azimuth of the polarization ellipse is indeterminate. The azimuth gradient is solenoidal around the polarization singular point. In metrology, shear interferometry enables the visualization of phase gradients in optical beams. Since the polarization azimuth gradient is related to the Stokes phase gradient, we adopt the shear interferometry technique to visualize these phase gradients for the detection of polarization singularity. We use a wedge plate lateral shear interferometer (LSI) in our experiments for the detection of the ellipse and vector field singularities. Being a self-referencing and intensity-based technique, this method is convenient for practical use. Unlike the traditional Stokes polarimetry method, where the polarization distribution at every spatial point is evaluated, this technique can distinguish degenerate states of polarization singularities simply by visual observation of intensity fringes. Index and helicity measurement of these polarization singularities without using polarization measurement methods are novel aspects of this scheme. Both theoretical and experimental results are presented to support our claim.

Dephasing Dynamics Accessed by High Harmonic Generation: Determination of Electron-Hole Decoherence of Dirac Fermions.

We reveal the critical effect of ultrashort dephasing on the polarization of high harmonic generation in Dirac fermions. As the elliptically polarized laser pulse falls in or slightly beyond the multiphoton regime, the elliptically polarized high harmonic generation is produced and exhibits a characteristic polarimetry of the polarization ellipse, which is found to depend on the decoherence time T2. T2 could then be determined to be a few femtoseconds directly from the experimentally observed polarimetry of high harmonics. This shows a sharp contrast with the semimetal regime of higher pump intensity, where the polarimetry is irrelevant to T2. An access to the dephasing dynamics would extend the prospect of high harmonic generation into the metrology of a femtosecond dynamic process in the coherent quantum control.

Peculiarities of the spectrum of reflected and transmitted light of circular polarization for a thin layer of an anisotropic wurtzite-type crystal near phonon resonance

Background. Polaritons attract the attention of researchers and engineers with their unique properties and promising applications in the field of micro- and nanoelectronics. Such applications could include devices such as transistors or even polaritons lasers, as have been reported in the scientific literature.
 Aim. The work analyzes the frequency reflection spectra upon excitation of polaritons, and also considers the change in the polarization ellipse upon reflection of circularly polarized light from an anisotropic crystal.
 Methods. Based on the wave equation in an anisotropic medium, a dispersion equation for polaritons is derived. To calculate energy reflection coefficients using the characteristic matrix method.
 Results. An aluminum nitride AlN crystal was chosen as the object of analysis. It is shown that the use of circularly polarized incident radiation makes it possible, using an anisotropic crystal, to change the nature of polarization from circular to almost linear polarization.
 Conclusion. The found dependence of the polarization of reflected light can be used in electronic devices based on polaritons.

OPTIMISATION OF OPTICAL INFOCOMMUNICATION NETWORKS

The article reviews existing approaches to network analysis, taking into account the topological properties of networks. A sequential analysis from a network link to the properties of a set of network links is carried out. The network link is analysed as a set of optical channels, and an analytical description of the transmission quality in such a channel is carried out. A model for calculating crosstalk in the paths of information and communication optical networks is proposed. As can be seen from the results, for an optical fibre of a given length, there is a number of steps for selecting the input polarisation ellipse for which the efficiency of the method is maximised. Also, with an increase in the number of steps, we observe a decrease in the efficiency of this compensation method. So, for an optical fibre of a given length at constant dynamics, there is a number of input signal polarisation ellipses for which the polarisation-mode dispersion will be minimal. For a particular fibre, this parameter (the number of input signals) must be selected, because this value is different for different fibres (within the range of 15-30 points).

Terahertz metasurface polarization detection employing vortex pattern recognition

The manipulation and detection of polarization states play a crucial role in the application of 6G terahertz communication. Nonetheless, the development of compact and versatile polarization detection devices capable of detecting arbitrary polarizations continues to be a challenging endeavor. Here, we demonstrate a terahertz polarization detection scheme by performing mode purity analysis and multidimensional analysis of the transmitted vortex field. The power of the proposed polarization recognition is verified by using three polarization trajectories, including linear polarizations, circular polarizations, and elliptical polarizations. Using the reconstructed complete polarization parameters, the detected polarization states are characterized using polarization ellipses, Poincaré sphere, and full-Stokes parameters. The experimental results validate the power of this scheme in polarization detection. This scheme holds promise for applications in polarization imaging and terahertz communication.

Effect of light ellipticity and polarization angle on the transient dynamics of the ground-state Hanle effect

We report theoretical investigations on the transient dynamics of the ground-state Hanle effect in the Voigt geometry, where a time-varying scanning magnetic field B (t) is applied perpendicular to the light propagation direction. Transient Hanle signals are calculated for different light polarizations using a theoretical model based on the density matrix approach. First, we study the ellipticity dependence of transient Hanle signals in two configurations in which the major axis of the light polarization ellipse () is aligned either perpendicular or parallel to the field B . For B , elliptical polarization of the light produces oscillations of frequencies 2ΩL(t) and ΩL(t) simultaneously, where ΩL(t) is the Larmor frequency of the corresponding field B (t). On the other hand, in the case of || B , only ΩL(t) oscillation is observed using elliptically polarized light. Second, we vary the tilt angle between the polarization vector of a linearly polarized light and the orientation of the field B and study its effect on the transient response of Hanle signals. Both the amplitude and the decay rate of the oscillations show a strong dependence on the light ellipticity and tilt angle of the polarization vector. In addition, the influence of the magnetic field sweep rate on the transient signals is demonstrated for given values of light ellipticity and polarization angle.