Arbitrary Polarization Research Articles

Full‐Phase Parameter Modulation with Arbitrary Polarization Combination via Bidirectional Asymmetric Transmission Meta‐Devices

AbstractThe bidirectional asymmetric transmission (BAT) meta‐devices have attracted widespread attention as an emerging display, encryption, and information storage platform. Generally, the multiplexing capability of BAT meta‐devices determines the upper limit of the loading capacity of multi‐task integrated systems. However, existing BAT meta‐devices still depend on structural properties and the arrangement of meta‐atoms, limiting the number of manipulated channels, operating frequency, and polarization combinations. Herein, a universal BAT meta‐device, enabling bidirectional eight‐phase‐channel asymmetric transmission, composed of bilayer spatially cascaded birefringent metasurfaces (BMs) is proposed to allow for arbitrary polarization combination via the inverse design method and validated in the microwave region. In addition, the polarization multiplexing capabilities of BAT meta‐devices are further extended via a Lego‐like physical mechanism. The proposed design strategy may facilitate BAT meta‐devices functional innovation and advanced application deployment in holographic images, duplex communication, and secret‐key‐sharing data encryption.

Full Stokes Mid-Wavelength Infrared Polarization Photodetector Based on the Chiral Dielectric Metasurface

Conventional imaging techniques can only record the intensity of light while polarization imaging can record the polarization of light, thus obtaining a higher dimension of image information. We use the COMSOL software to numerically propose a circular polarization photodetector composed of the dislocated 2-hole Si chiral metasurfaces controlling the circular polarization lights and the HgCdTe (MCT) photodetector chip to detect the intensity of light signals. The chiral metasurfaces can be equated to a significant radiation source of the Z-type current density under the right circularly polarized incidence conditions, which explains the large circular dichroism (CD) of absorption of 95% in chiral photodetectors. In addition, the linear dichroism (LD) of the linear polarization pixel is 0.62, and the extinction ratio (ER) is 21 dB. The full Stokes pixel using the six-image-element technique can almost measure arbitrary polarization information of light at 4 μm operation wavelength. Our results highlight the potential of circular dichroic metasurfaces as photonic manipulation platforms for miniaturized polarization detectors.

Polarized ZZ pairs in gluon fusion and vector boson fusion at the LHC

Pair production of helicity-polarized weak bosons (Vλ=Wλ±,Zλ) from gluon fusion (gg→VλVλ′′) and weak boson fusion (V1V2→VλVλ′′) are powerful probes of the Standard Model, new physics, and properties of quantum systems. Measuring cross sections of polarized processes is a chief objective of the Large Hadron Collider's (LHC) Run 3 and high luminosity programs, but progress is limited by the simulation tools that are presently available. We propose a method for computing polarized cross sections that works by directly modifying Feynman rules instead of (squared) amplitudes. The method is applicable to loop-induced processes, and can capture the interference between arbitrary polarization configurations, interference with non-resonant diagrams, as well as off-shell/finite-width effects. By construction, previous results that work at the (squared) amplitude level are recoverable. As a demonstration, we report the prospect of observing and studying polarized ZλZλ′ pairs when produced via gluon fusion and electroweak processes in final-states with four charged leptons at the LHC, using the new method to simulate the gluon fusion process. Our Feynman rules are publicly available as a set of Universal FeynRules Object libraries called SM_Loop_VPolar.

Birefringence compensation method of test-mass substrates for gravitational wave detectors with arbitrary polarization states.

GW detectors are ultimately limited by thermal noise in their most sensitive region. Cryogenic operation combined with crystalline substrates and coatings is a promising approach to reduce this noise, thereby increasing their sensitivity and detection rate. However, crystalline materials can exhibit birefringent behaviors which will degrade the detector's sensitivity. Here, we demonstrate the use of a pair of identical electropolarization retarders to generate arbitrary polarization states and compensate birefringence of a KAGRA test-mass substrate.

Efficient Second‐Harmonic Generation with Weak Polarization Sensitivity in Gallium Nitride Metasurfaces via Bound States in the Continuum

AbstractBound states in the continuum (BICs) are widely exploited in all‐dielectric metasurfaces to significantly enhance the Q‐factor and second harmonic generation (SHG). However, a higher SHG conversion efficiency is overshadowed by the narrow transparency window of all‐dielectric materials and strict requirement of polarization‐matching. Herein, an augmented SHG assisted is demonstrated by symmetry‐protected quasi‐BICs from z‐cut wurtzite GaN metasurfaces, whose wide transparent range suppresses self‐absorption of second harmonic. Strong resonances emerge under both X‐ and Y‐polarized excitations, where the multipole characters of each eigenmode are quantitatively identified via decomposition simulations. The local field enhancement enabled by the extreme energy confinement of quasi‐BICs contributes to an efficient SHG, recording a conversion efficiency up to 2 × 10−7 at moderately low input peak intensity (≈1 GW cm−2), orders of magnitude larger than bulk GaN. With proper design, the overlapping X‐ and Y‐polarized resonances can support SHG from excitation with arbitrary polarizations. The alleviation of polarization‐matching remarkably enhances the SHG power by 66.2% under unpolarized illumination condition. The results of intense SHG reveal GaN as a promising candidate for high‐performance nanoscale nonlinear photonic devices. The weak polarization sensitivity of the designed structure will chart a novel course for the advancement of next‐generation efficient all‐dielectric metasurfaces.

Multifunctional Meta-Devices for Full-Polarization Rotation and Focusing in the Near-Infrared.

The creation of multi-channel focused beams with arbitrary polarization states and their corresponding optical torques finds effective applications in the field of optical manipulation at the micro-nanoscale. The existing metasurface-based technologies for polarization rotation have made some progress, but they have been limited to single functions and have not yet achieved the generation of full polarization. In this work, we propose a multi-channel and spatial-multiplexing interference strategy for the generation of multi-channel focusing beams with arbitrary polarization rotation based on all-dielectric birefringent metasurfaces via simultaneously regulating the propagation phase and the geometric phase and independently controlling the wavefronts at different circular polarizations. For the proof of concept, we demonstrate highly efficient multi-channel polarization rotation meta-devices. The meta-devices demonstrate ultra-high polarization extinction ratios and high focusing efficiencies at each polarization channel. Our work provides a compact and versatile wavefront-shaping methodology for full-polarization control, paving a new path for planar multifunctional meta-optical devices in optical manipulation at micro-nano dimensions.

Deterministic preparation of optical qubits with coherent feedback control

We propose a class of preparation schemes for orbital angular momentum and polarization qubits carried by single photons or classical states of light based on coherent feedback control by an ancillary degree of freedom of light. The preparation methods use linear optics and include the transcription of an arbitrary polarization state onto a two-level OAM system (swap) for arbitrary OAM values ±ℓ within a light beam, i.e., without a spatial interferometer. The preparations can be carried out with unit efficiency independent from the potentially unknown initial state of the system. The swap scheme also allows us to implement arbitrary unitary gates on OAM qubits (±ℓ) by reducing them to polarization gates. In addition, we show how to translate measurement-based qubit control channels into coherent feedback schemes for optical implementation.

An ultra-wideband reflective polarization conversion metasurface and its application in RCS reduction

ABSTRACT In this work, an ultra-wideband reflective polarization conversion metasurface (PCM) is proposed at first. Because the PCM is an anisotropic structure that is symmetric with respect to both x- and y-axes, and the reflection phase difference under x- and y-polarized incidences is close to 180° in an ultra-wide frequency range, the PCM can achieve both linear polarization conversion and circular-polarization (CP) maintaining reflection in the ultra-wide frequency band from 8.3 to 41.3 GHz except for near the frequency point of 38.8 GHz. Moreover, when its unit cell structure is rotated by 90°, its cross-polarized reflection coefficient under LP incidence, together with the co-polarized reflection coefficient under CP incidence, will be changed by almost 180° in phase. Thus, based on the PCM, an ultra-wideband coding diffusion metasurface (CDM) is further proposed for radar cross section (RCS) reduction. The simulation and experiment results indicate that the CDM can achieve effective RCS reduction in the ultra-wide frequency band of 8.2–41.7 GHz under normal incidence with arbitrary polarization; in addition, an ultra-wideband RCS reduction can still be realized under oblique incidence with an incident angle less than 45°, which shows that the CDM is of good application value in radar stealth technology.

Omni-polarized Faraday isolator based on non-Hermitian Faraday system

Non-Hermitian systems have recently attracted significant attention in photonics due to the realization that the interplay between gain and loss can lead to entirely new and unexpected features. Here, we propose and demonstrate a non-Hermitian Faraday system capable of non-reciprocal omni-polarizer action at the exceptional point. Notably, both forward and backward propagating light with arbitrary polarization converge to the same polarization state. Leveraging the robustness and non-reciprocity of the non-Hermitian Faraday system, we realize an omni-polarized Faraday isolator that can effectively isolate any polarized light without the need for a polarizer at the incident port of backward propagation. Remarkably, under the given parameter configuration, the isolator achieves a maximum isolation ratio of approximately 100 dB and a minimum isolation ratio of around 45 dB for various polarized light, accompanied by near-zero insertion loss. Furthermore, our research reveals the remarkable tolerance of the non-Hermitian Faraday isolator to nonlinear effects. This unique characteristic allows us to harness nonlinear effects to achieve various optical functions, all while maintaining excellent isolation performance. The proposed non-Hermitian Faraday system paves the way for the realization of magnetically or optically switchable non-reciprocal devices.

Broadband four-shoulder sine antenna of radio monitoring and direction finding equipment with a note system of two orthogonally combined printed resistance transformers

Problem statement. The article presents material on the development of antennas used in radio monitoring and radio direction finding equipment of electronic warfare equipment. The basic requirements for the design and characteristics of antennas of radio monitoring and direction finding equipment are presented. Aspects of the fundamentals of the development of a four-arm broadband antenna powered by two orthogonally combined printed resistance transformers, which has not been used before, for the possibility of controlling polarization, are considered, the results of modeling the developed antenna are presented and recommendations for its use in the antenna array are given. Purpose. To develop a small-sized antenna that allows to increase the efficiency of the operation of radio direction finding and radio monitoring complexes in an ultra-wide frequency band, with a special power supply system of two orthogonally combined printed resistance transformers for the possibility of implementing polarization control. Results. Based on the methods of electrodynamic modeling, computational methods of technical electrodynamics, methods of full–scale experimental measurements of antenna characteristics and methods of computer processing of data of full-scale experimental measurements, an antenna has been developed that allows the control of amplitude, phase and polarization parameters in an ultra-wide frequency band. The developed antenna is based on a flat four-arm sine element with a power supply system of two orthogonally arranged printed resistance transformers. The resistance transformer significantly reduces the level of the reflection coefficient at the input and radiation losses. The use of this development in radio direction finding and radio monitoring complexes will reduce the number of sublattices of the antenna system due to the functioning of its elements in an ultra-wide frequency band. The practical significance lies in reducing the number of letters of radio direction finding antenna systems consisting of the developed antenna elements, minimizing the degree of distortion of ultra-wideband signals and ultrashort pulses of arbitrary (varying) polarization received by antenna devices and systems from the antenna presented in the article. The developed antenna and antenna devices based on it can be used for electronic warfare, as well as improving communication and remote control systems.

Optimal Spin Polarization Control for the Spin-Exchange Relaxation-Free System Using Adaptive Dynamic Programming.

This work is the first to solve the 3-D spin polarization control (3DSPC) problem of atomic ensembles, which controls the spin polarization to achieve arbitrary states with the cooperation of multiphysics fields. First, a novel adaptive dynamic programming (ADP) structure is proposed based on the developed multicritic multiaction neural network (MCMANN) structure with nonquadratic performance functions, as a way to solve the multiplayer nonzero-sum game (MP-NZSG) problem in 3DSPC under the constraints of asymmetric saturation inputs. Then, we utilize the MCMANNs to implement the multicritic multiaction ADP (MCMA-ADP) algorithm, whose convergence is proven by the compression mapping principle. Finally, the MCMA-ADP is deployed in the spin-exchange relaxation-free (SERF) system to provide a set of control laws in 3DSPC that fully exploits the multiphysics fields to achieve arbitrary spin polarization states. Numerical simulations support the theoretical results.

Robust broadband dual-polarized rectenna with high conversion efficiency

In this paper, a robust wide-beam dual-polarized broadband rectenna with high conversion efficiency is proposed. First, a metal wall-loaded broadband cross-dipole antenna is designed as the receiving antenna. With the metal wall, the bandwidth of the receiving antenna is greatly improved. The measured results show that the −10 dB impedance bandwidth is 820 MHz from 1.65 to 2.47 GHz, and the 3-dB beamwidth is over 80° within the operating bandwidth. Besides, a novel impedance matching network is introduced to help the rectifier achieve high conversion efficiency in a wide bandwidth. The measured results show that the RF-DC conversion efficiency is maintained above 50 % with a maximum of 78 % within the bandwidth from 1.56 to 2.53 GHz when the load impedance is 840 Ω and the input power is 12.0 dBm. Finally, the receiving antenna and rectifier are integrated and measured. The results illustrate that the proposed design can be robustly against dynamic ambient power density, large oblique incidence angle, and arbitrarily polarized wave. Specifically, the measured conversion efficiency is over 49 % at an ambient power density of 200 μW/cm2 within the incident angle from −40° to 40° under arbitrary polarization. Hence, it could be a feasible solution to wireless energy harvesting (WEH) applications.

Digital calibration method to enable depth-resolved all-fiber polarization sensitive optical coherence tomography with an arbitrary input polarization state

We present a fully integrated depth-resolved all fiber-based polarization sensitive optical coherence tomography (PSOCT). In contrast to conventional fiber-based PSOCT systems, which require additional modules to generate two or more input polarization states, or a pre-adjustment procedure to generate a circularly polarized light, the proposed all-fiber PSOCT system can provide depth-resolved birefringent imaging using an arbitrary single input polarization state. Utilizing the discrete differential geometry (DDG)-based polarization state tracing (PST) method, combined with several geometric rotations and transformations in the Stokes space, two problems induced by the optical fibers can be mitigated: 1) The change in the polarization state introduced by the optical fibers can be effectively compensated using a calibration target at the distal end of the probe, and the computations of the local axis orientation and local phase retardation can be achieved with a single arbitrary input polarization state, eliminating the need for a pre-defined input polarization state, allowing a flexible system design and user-friendly experimental procedure; 2) The polarization mode dispersion (PMD) induced by the optical fibers can be compensated digitally without the requirement of additional input polarization states, providing an accurate PSOCT imaging result. To demonstrate the performance of the proposed method, the depth resolved PSOCT results of a plastic phantom and in vivo skin imaging are obtained using the proposed all-fiber PSOCT system.

Entangling entanglement: coupling frequency and polarization of biphotons on demand

Quantum information is often carried in the frequency and polarization degrees of freedom (DoFs) in single photons and entangled photons. We demonstrate an approach to couple and decouple the frequency and polarization DoFs of broadband biphotons. Our approach is based on a nonlinear interferometer consisting of a linear dispersive medium and a polarization controller in between the two biphoton sources (nonlinear media). When the two DoFs are decoupled, maximally polarization-entangled biphotons are observed in the polarization DoF, while interference fringes are observed in the spectrum of the biphotons. When the two DoFs are coupled, by adjusting the polarization controller, interference fringes disappear from the spectrum and instead appear in the degree of polarization entanglement, varying between 0 and 1, depending on the signal and idler frequencies. Our approach offers a convenient means of tuning the polarization entanglement and can be employed for arbitrary biphoton polarization state generation.

Dynamic Polarization Patterning Technique for High-Quality Liquid Crystal Planar Optics

The Pancharatnam–Berry (PB)-phase liquid crystal (LC) planar optical elements, featuring large apertures and a light weight, are emerging as the new generation optics. The primary method for fabricating large-aperture LC planar optical elements is through photo-alignment, utilizing polarization laser direct writing. However, conventional polarization direct writing suffers from an inertia-induced stopping step during splicing, leading to suboptimal optical effects. Here, we propose a novel highly efficient method for arbitrary polarization patterning, significantly reducing interface splicing errors in these optical elements. (We call it dynamic polarization patterning technology). This process involves simultaneous mobile splicing and real-time generation of different polarization patterns for exposure, eliminating the inertia-related splicing interruption. As a demonstration, we fabricated a lens with an aperture of approximately 1 cm within 30 min at 633 nm. Furthermore, we developed a 100% fill-factor lens array (3 × 3) with an element lens diameter of approximately 7 mm within 1.5 h at 532 nm. Their focal lengths were uniformly set at 30 cm, demonstrating superior convergence capabilities within their designated working wavelengths, alongside commendable performance in converging light across various other wavelengths. Our measurements confirmed the good focusing performance of these samples. The convergence spot size of the lens deviated by approximately 40% from the theoretical diffraction limit, whereas the lens array exhibited a deviation of around 30%. The dynamic polarization direct writing during uniform platform movement reduced splicing errors to a mere 100–200 nm. The enhancement in imaging quality can be primarily attributed to the innovative use of mobile polarization splicing exposure technology, coupled with the inherent self-smoothing properties of LC molecules. This synergy significantly mitigates the impact of seam diffraction interference.

Enhanced Light-Matter Interaction in Metallic Nanoparticles: A Generic Strategy of Smart Void Filling.

The intrinsic properties of materials play a substantial role in light-matter interactions, impacting both bulk metals and nanostructures. While plasmonic nanostructures exhibit strong interactions with photons via plasmon resonances, achieving efficient light absorption/scattering in other transition metals remains a challenge, impeding various applications related to optoelectronics, chemistry, and energy harvesting. Here, we propose a universal strategy to enhance light-matter interaction, through introducing voids onto the surface of metallic nanoparticles. This strategy spans nine metals including those traditionally considered optically inactive. The absorption cross section of void-filled nanoparticles surpasses the value of plasmonic (Ag/Au) counterparts with tunable resonance peaks across a broad spectral range. Notably, this enhancement is achieved under arbitrary polarizations and varied particle sizes and in the presence of geometric disorder, highlighting the universal adaptability. Our strategy holds promise for inspiring emerging devices in photocatalysis, bioimaging, optical sensing, and beyond, particularly when metals other than gold or silver are preferred.

Optical Stern–Gerlach Effect in Periodically Poled Electro‐Optical Crystals

AbstractThe Stern–Gerlach (SG) effect provided the first direct experimental evidence of the quantization of electron spin. Although some analog SG effects have been proposed in optical systems, finding a perfect optical analog for the SG effect remains a challenge. Here, a novel optical SG effect is demonstrated in periodically poled electro‐optical crystals. Induced by an applied electric field, the principal axes of crystal rock periodically along the propagation direction of light. When the quasi‐phase‐matching condition is satisfied, the electro‐optical coupling process within the periodically poled crystal can be accurately described by the Schrödinger–Pauli equation for spin‐1/2 particles. The output photons can be deflected toward opposite directions according to their intrinsic spin angular momentum (circular polarizations), since the transversely varying duty cycle of crystal arises an effective magnetic‐field gradient. Moreover, the output photons can be separated according to two arbitrary orthogonal polarization states, allowing us to construct high‐speed electro‐optically tunable polarization beam splitters for arbitrary orthogonal polarization states. Therefore, the optical SG effect provides not only a perfect optical analog for the quantum SG effect but also a useful optical element for optics and quantum physics.

Theoretical efficiency limit of diffractive input couplers in augmented reality waveguides.

Considerable efforts have been devoted to augmented reality (AR) displays to enable the immersive user experience in the wearable glasses form factor. Transparent waveguide combiners offer a compact solution to guide light from the microdisplay to the front of eyes while maintaining the see-through optical path to view the real world simultaneously. To deliver a realistic virtual image with low power consumption, the waveguide combiners need to have high efficiency and good image quality. One important limiting factor for the efficiency of diffractive waveguide combiners is the out-coupling problem in the input couplers, where the guided light interacts with the input gratings again and get partially out-coupled. In this study, we introduce a theoretical model to deterministically find the upper bound of the input efficiency of a uniform input grating, constrained only by Lorentz reciprocity and energy conservation. Our model considers the polarization management at the input coupler and can work for arbitrary input polarization state ensemble. Our model also provides the corresponding characteristics of the input coupler, such as the grating diffraction efficiencies and the Jones matrix of the polarization management components, to achieve the optimal input efficiency. Equipped with this theoretical model, we investigate how the upper bound of input efficiency varies with geometric parameters including the waveguide thickness, the projector pupil size, and the projector pupil relief distance. Our study shines light on the fundamental efficiency limit of input couplers in diffractive waveguide combiners and highlights the benefits of polarization control in improving the input efficiency.

Poincaré sphere trajectory encoding metasurfaces based on generalized Malus’ law

As a fundamental property of light, polarization serves as an excellent information encoding carrier, playing significant roles in many optical applications, including liquid crystal displays, polarization imaging, optical computation and encryption. However, conventional polarization information encoding schemes based on Malus’ law usually consider 1D polarization projections on a linear basis, implying that their encoding flexibility is largely limited. Here, we propose a Poincaré sphere (PS) trajectory encoding approach with metasurfaces that leverages a generalized form of Malus’ law governing universal 2D projections between arbitrary elliptical polarization pairs spanning the entire PS. Arbitrary polarization encodings are realized by engineering PS trajectories governed by either arbitrary analytic functions or aligned modulation grids of interest, leading to versatile polarization image transformation functionalities, including histogram stretching, thresholding and image encryption within non-orthogonal PS loci. Our work significantly expands the encoding dimensionality of polarization information, unveiling new opportunities for metasurfaces in polarization optics for both quantum and classical regimes.

Arbitrary Polarization Conversion by the Photonic Band Gap of the One-Dimensional Photonic Crystal

Arbitrary Polarization Conversion by the Photonic Band Gap of the One-Dimensional Photonic Crystal