Polarization State Research Articles

The role of excitation vector fields and all-polarisation state control in cavity magnonics

Recently the field of cavity magnonics, a field focused on controlling the interaction between magnons and photons confined within microwave resonators, has drawn significant attention as it offers a platform for enabling advancements in quantum- and spin-based technologies. Here, we introduce excitation vector fields, whose polarisation and profile can be easily tuned in a two-port cavity setup, thus acting as an effective experimental dial to explore the coupled dynamics of cavity magnon-polaritons. Moreover, we develop theoretical models that accurately predict and reproduce the experimental results for any polarisation state and field profile within the cavity resonator. This versatile experimental platform offers a new avenue for controlling spin-photon interactions by manipulating the polarisation of excitation fields. By introducing real-time tunable parameters that control the polarisation state, our experiment delivers a mechanism to readily control the exchange of information between hybrid systems.

Spontaneous Symmetry Breaking of an Optical Polarization State in a Polarization-Selective Nonlinear Reson

Spontaneous Symmetry Breaking of an Optical Polarization State in a Polarization-Selective Nonlinear Reson

Development of a Wollaston phase grating polarized interferometer for simultaneous generation of interferograms

Wollaston phase-grating interferometer is introduced to measure of the optical phase across various samples. The system employs a Wollaston prism to create two angularly separated beams and with orthogonal linear polarizations. Working as a quasi-common-path interferometer, one of these beams serves as a reference while the other acts as the sample. Circular polarization states are induced in each beam using a quarter-wave plate. Both beams are directed onto a 4-f imaging system, within which a 2D phase grating is positioned at the Fourier plane. This 2D grating enables the superposition of the two beams, generating a polarized interferogram. The characteristics of the diffractive elements cause the grating to produce replicas of interference patterns, which are centered around the diffraction orders of the 2D phase grating itself. Due to the presence of interference patterns with inherent π phase shifts, this configuration reduces the number of polarizers needed to implement phase shifting methods. It is shown that by using two polarizers it is possible to generate four phase shifts. A polarizer oriented at 0° covers two of the replicas and another polarizer oriented at π/4 covers the remaining interferograms. This configuration introduces phase shifts of ξ1 = 0, ξ2 = π/2, ξ3 = π and ξ4 = 3π/2. Results obtained for static and dynamic samples are presented, as well as the corresponding statistics on the repeatability of the configuration.

Soil moisture retrieval over croplands using novel dual-polarization SAR vegetation index

Synthetic Aperture Radar (SAR) data, known for its high spatial resolution and all-weather observation capabilities, holds immense promise in soil moisture monitoring. The Water Cloud Model (WCM) is widely applied in soil moisture inversion using SAR data. However, the optical vegetation indices employed in traditional WCM cannot synchronize with SAR data, and the polarimetric scattering information contained in current SAR vegetation indices is incomplete, consequently compromising the accuracy of SAR-based soil moisture retrieval. Therefore, this study proposes a method for soil moisture retrieval over cropland using a novel dual-polarization SAR vegetation index. The method initially combines SAR data covariance elements with backscatter information to establish a polarization scattering contrast parameter (mcp). Then, based on mcp and incorporating the degree of polarization, a polarization scattering correlation contrast parameter (Rcp) is defined. Rcp integrates the distinctive features of scattering differences and polarization states. Building on Rcp, a novel dual-polarization SAR vegetation index (DRVIs) is introduced. Ultimately, DRVIs are utilized in the WCM to achieve surface soil moisture retrieval in cropland. This research conducts experiments in four crop cover areas of the Carman test site in Canada, namely soybean, wheat, canola, and corn. Under VV and VH polarizations, the overall correlation coefficients between measured in-situ data and SSM estimates reach 0.89 and 0.84, respectively. Compared to SSM estimates based on NDVI and LAI products, SSM estimates based on DRVIs exhibit a notable improvement in accuracy, with enhancements of approximately 7.2% and 12.7%, respectively. This novel DRVIs is poised to expand the utilization of SAR data in monitoring vegetation growth and soil moisture retrieval.

Dual–resonance enhancement and polarization control of upconversion luminescence of NaYF4:Yb,Er nanoparticles on 2D metal gratings

In this work, we report enhancement and polarization control of multi–color (green/red) upconversion luminescence (UCL) of lanthanide–doped (NaYF4:Yb,Er) nanoparticles by dual–resonance modes of surface plasmons (SP) on two–dimensional (2D) metal gratings in orthogonal directions. Investigations are performed for the SP resonance modes to be tuned, by adjusting the grating periods, to match any one or two of the green–UCL, red–UCL and excitation wavelengths. It is shown that, for the upconversion nanoparticles (UCNPs) on the 2D gratings with both of the dual resonance modes matching the green–/red–UCL or excitation wavelength, enhancements of the UCLs are roughly doubled, compared with their one–dimensional (1D) counterparts. And when the dual resonance modes match the green– or red–UCL and the excitation wavelength, enhancements of the UCLs are further greatly improved, in spite that the resonance modes for the excitation and emission light are in orthogonal directions. As the emitted UCL photons are largely coupled with the dual SP resonance modes, the radiated green– and red–UCL light can be distinguished by their linear polarization states in orthogonal directions. It is also indicated that polarization of the excitation light can influence the polarization of the UCL light when coupled with the SP resonance modes.

Cholesterol overload in macrophages drives metabolic dysfunction-associated steatohepatitis via inhibiting 7-dehydrocholesterol reductase in mice

BackgroundDietary cholesterol promotes metabolic dysfunction-associated steatohepatitis (MASH), with hepatic macrophages central to disease pathology. However, the mechanisms by which cholesterol-loaded macrophages influence MASH remain unclear.MethodsIn this study, mice were fed a cholesterol-rich choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD). Hepatic cholesterol levels, inflammatory markers, and pro-inflammatory macrophage polarization were assessed. In vitro studies examined the impact of cholesterol on macrophage polarization, identifying 7-dehydrocholesterol reductase (DHCR7) as a key cholesterol- and inflammation-responsive enzyme. DHCR7 expression in macrophages from MASH patients and model mice was evaluated. Functional studies involving in vitro knockdown and overexpression experiments, were complemented using myeloid-specific DHCR7 knockout mice. RNA sequencing was performed on liver tissues from wild-type and DHCR7 knockout mice to identify affected signaling pathways.ResultsCDAHFD-fed mice exhibited local cholesterol accumulation and a pro-inflammatory macrophage phenotype in the liver. Cholesterol overload in vitro promoted M1 polarization and liver inflammation, reversible by simvastatin. DHCR7 expression, responded to cholesterol and polarization state, was downregulated in M1-polarized and hepatic macrophages from MASH patients and mice. DHCR7 suppression promoted pro-inflammatory phenotype, while its overexpression showed anti-inflammatory effects. Myeloid-specific DHCR7 deficiency in CDAHFD-fed mice worsened liver inflammation and pro-inflammatory macrophage infiltration. RNA sequencing identified the phosphoinositide 3-kinase (PI3K) pathway in DHCR7-regulated effects, with DHCR7-PI3K axis activation mitigating cholesterol-driven inflammation.ConclusionsThese findings unveil novel mechanistic insights into MASH pathogenesis, suggesting targeting macrophage-specific DHCR7 activation may offer a promising therapeutic strategy for MASH.

Teratoma Development in 129.MOLF-Chr19 Mice Elicits Two Waves of Immune Cell Infiltration

Teratomas are a highly differentiated type of testicular germ cell tumors (TGCTs), the most common type of solid cancer in young men. Prominent inflammatory infiltrates are a hallmark of TGCTs, although their compositions and dynamics in teratomas remain elusive. Here, we reached out to characterize the infiltrating immune cells and their activation and polarization state by using high-throughput gene expression analysis of 129.MOLF-Chr19 mice that spontaneously develop testicular teratomas. We showed that inconspicuous testes without any apparent alterations in size or morphology can be clustered into three groups based on their expression of stemness and immune genes, supporting a model in which initial oncogenic transformation elicits a first wave of T-cell infiltration. Moderately and severely enlarged tumorous testes then displayed a progressive infiltration with T cells, monocytes/macrophages, and B cells. Importantly, T cells seem to adopt an inactive state caused by an overexpression of immune checkpoint molecules and the polarization of monocytes/macrophages to an anti-inflammatory phenotype. Our findings are supported by the analysis of metabolic gene expression, which unveiled alterations indicative of tumor growth and immune cell infiltration. Collectively, testicular teratomas, at least in mice, are characterized by a diverse inflammatory infiltrate containing T cells that putatively become inactivated, allowing the tumors to further grow. We believe that these findings may provide a rationale for the development of new immunomodulatory therapies for TGCTs.

Shape Measurement of Single Gold Nanorods in Water Using Open-Access Optical Microcavities.

Shape measurement of single nanoparticles in fluids is an outstanding challenge with applications in characterizing synthetic functional nanoparticles and in early warning detection of rod-shaped pathogens in water supplies. Here we introduce a novel technique to measure the aspect ratio of rod-shaped particles by analyzing changes in the polarization state of a laser beam transmitted through an optical microcavity through which the particle diffuses. The resolution in aspect ratio measurement is found to be around 1%. Our work opens the new possibility of in situ and single-particle shape measurement, which has promising applications in nanoparticle characterization, water monitoring, and beyond.

Manifestation of super chiral exceptional points in a plasmonic metasurface

The exceptional point (EP), a degenerate point within non-Hermitian parametric space, has attracted considerable attention, especially for its chiral responses. However, achieving ideal circular dichroism (CD) remains challenging due to the existence of parallel components at the EP. Here, we delve into the theoretical condition required to attain a zero-transmission parallel component. This condition, together with the chiral EP condition, leads to a point characterized by near-unity CD, termed the super chiral EP (SCEP). To illustrate our theoretical framework, we introduce a parity-time symmetric metasurface with gain and loss. The observation of SCEP is demonstrated by tuning both the coupling strength and gain–loss ratio. Furthermore, we explore distinctive properties of SCEP, including phase flip and unidirectional invisibility. Leveraging SCEP and the topological phase transition point, we achieve polarization states across the entire Poincaré surface. This work opens avenues for potential applications in polarizing optical elements, holography, logic gates, chiral molecular detection, ultrasensitive sensing, and polarization-sensitive imaging.

100 Gb/s/λ polarization multiplexing PON downlink based on simplified heterodyne coherent reception

In this work, we experimentally demonstrate a 100Gb/s/λ downstream transmission link for coherent passive optical networks (PONs) up to 50 km, achieving an optical power budget of 29 dB through polarization multiplexing (PolMux) of two 50 Gb/s channels using multiband carrierless amplitude phase modulation (multiCAP) and optical single side band (OSSB) modulation. Additionally, we introduce a separate PolMux 50 Gb/s link that presents an optical power budget of 38.7 dB. Both links have been achieved using a simplified polarization-demultiplexing heterodyne coherent receiver. The robustness of the system is experimentally evaluated by analyzing its response to various input states of polarization. The transmission has been accomplished using 10 GHz electrical bandwidth devices at both the transmission and receiving ends, thereby paving the way for low-cost 100G links suitable for applications such as PONs.

Adjustable repetition rate mode-locked fiber laser using a ZnO nanolaminate

This paper experimentally demonstrates the use of a zinc oxide (ZnO) nanolaminate as a polarization-dependent loss element to control the frequency repetition rate in a passive mode-locked fiber laser. The ZnO nanolaminate was deposited via the atomic layer deposition technique. The system achieves repetition frequencies ranging from 2.2 to 6.6 MHz, with emission peaks occurring at wavelengths between 1569.1 nm and 1570.8 nm, exhibiting three to four peaks. The fiber exhibits a minimal pulse duration of around 9.78 ns; the maximal pulse-to-pulse separation was 452 ns. The fiber laser demonstrates excellent stability in both power and wavelength emission. The compact experimental setup leverages the properties of the thin film of zinc oxide, offering a versatile laser system capable of quickly altering pulse repetition rates by simply adjusting the polarization state.

Full-space programmable circularly polarized metasurface for space-multiplexing wireless communications

The programmable metasurface has been proved to be an effective tool to dynamically tailor electromagnetic (EM) waves. However, how to achieve real-time and independent controls of circularly polarized (CP) waves in the transmission and reflection spaces is still a challenge. To address this problem, we propose a full-space programmable CP metasurface, which can independently manipulate the CP waves in transmission and reflection spaces in real time by controlling the bias voltage. The polarization states of reflected and transmitted CP waves can be independently customized through elaborate meta-atom design. As a proof of concept, we designed, fabricated, and measured a full-space programmable CP metasurface that can realize copolarized reflection for right-handed circularly polarized (RCP) waves and cross-polarized transmission for left-handed circularly polarized (LCP) waves. Simulated and measured results verify that the wavefronts of reflected and transmitted CP waves can be independently manipulated in real time by reprogramming the reflection and transmission phase coding sequences. Based on the full-space programmable CP metasurface, a space-multiplexing wireless communication scheme is established, successfully delivering two different images along preset reflection and transmission channels.

Theoretical and experimental study on optical polarization states in overhead optical cables under complex weather conditions such as real lightning

Abstract By analyzing the changes in three Stokes vectors, the trajectory of polarization state on the Poincaré sphere, and the polarization change rate, both theoretical and practical aspects of polarization state variations in signal light within optical fiber composite overhead power ground wires (OPGWs) during real thunderstorm conditions, were examined. Our findings reveal that lightning and mechanical vibrations both impact the polarization state of the signal light in OPGW. Theoretical models demonstrate that lightning induces polarization changes through the Faraday magneto-optic effect and exhibits nonlinear electro-optic effects, leading to a maximum polarization change rate of Mrad s−1. In contrast, mechanical vibrations cause long-term, low-intensity polarization rate changes, with a maximum polarization rate of Krad s−1, highlighting a significant optical birefringence effect. Digital signal processing algorithms for coherent receivers with over 100G polarization multiplexing provide valuable guidance for recovering polarization states.

Single-shot 3 × 3 Mueller matrix microscopy with color polarization encoding.

Snapshot retrieval of linear Stokes parameters in polarized light microscopy has benefited from recent advances in nanotechnology which have made polarization image sensors commercially available. However, real-time retrieval of the 3 × 3 Mueller matrix (MM) is limited by the need for time-sequential change in polarization states in the input. In the present Letter, we propose a cost-effective technique for the real-time retrieval of the 3 × 3 Mueller matrix by encoding linear polarization states in each of the three color channels of the source and analyzing light passing through the sample using a color polarization sensor placed in the imaging plane of a transmission microscope. Validation experiments for samples under real-time imaging conditions are presented. To the best of our knowledge, this is the first report on the snapshot 3 × 3 Mueller matrix element retrieval in polarized light microscopy by combining division of focal plane (DoFP) color polarimetric sensing and polarization color encoding of the source.

Investigation of Interface-Induced Helicity-Dependent Photocurrent and High-TC Ferromagnetism in Wafer-Scale 2D Ferromagnetic Fe4GeTe2/Bi2Te3 Heterostructures.

The helicity-dependent photocurrent (HDPC) of Fe4GeTe2 (3, 5, 8, 10 nm)/Bi2Te3 (8 nm) heterostructures grown on sapphire substrates was systematically investigated. It is revealed that the HDPC is induced by the interface coupling between the Fe4GeTe2 and Bi2Te3 films, and it is dominated by the circular photogalvanic effect (CPGE) rather than by the circular photodrag effect (circular photon drag effect). As the tensile strain increases, the CPGE current decreases, which can be attributed to the decrease of the interface-induced spin-orbit coupling with increasing tensile strain. In addition, it is demonstrated that by applying appropriate tensile strain, the 5 nm Fe4GeTe2/Bi2Te3 sample can be used to detect the circular polarization state of a light. Finally, Fe4GeTe2 (5, 8, and 10 nm)/Bi2Te3 (8 nm) heterostructures show a TC larger than 390 K. The dependence of the CPGE on the film thickness of Fe4GeTe2 is different from that of Curie temperature, indicating that the enhanced exchange interaction induced by the interface coupling may be the dominant mechanism for the high-TC ferromagnetism. The large interface-induced CPGE in the Fe4GeTe2/Bi2Te3 suggests that Fe4GeTe2/Bi2Te3 heterostructures may provide a good platform for designing novel opto-spintronic devices.

Polarization state tomography of Stokes–anti-Stokes photon pairs from degenerate four-wave mixing in diamond

Polarization state tomography of Stokes–anti-Stokes photon pairs from degenerate four-wave mixing in diamond

Non-Interleaved Shared-Aperture Full-Stokes Metalens via Prior-Knowledge-Driven Inverse Design.

Characterization of electromagnetic wave polarization states is critical in various applications of materials, biomedical, and imaging. The emergence of metasurfaces opens up the possibility of implementing highly integrated full-Stokes imagers. Despite rapid development, prevailing schemes on metasurface-based full-Stokes imagers require interleaved or cascaded designs, inevitably resulting in performance deterioration, bulky size, and complicating the imaging procedure due to misalignment. To overcome these challenges, a non-interleaved shared-aperture full-Stokes metalens enabled by the prior-knowledge-driven inverse design methodology is proposed. The metalens can be directly deployed into imagers, performing high-accuracy diffraction-limited full-Stokes imaging without other ancillary components, breaking intrinsic constraints of efficiency and resolution in interleaved design. To demonstrate this, the metalens is integrated into the W-band passive imaging system, as an alternative solution, to perform polarimetric imaging, which reduces the reliance on the high cost and high complexity of the ortho-mode transducer and broadband correlator in traditional polarimetric radiometers. Furthermore, with the assistance of a 3D reconstruction method, the feasibility of multi-polarization information for contactless surface slope measurements is explored. This work may open new paradigms for the full-Stokes imager designing and broaden the applications of metasurface polarimetric imaging.

Anisotropic Coupling‐Based 2D Material Dember Polarized Photodetectors

AbstractPolarization photodetectors (PPDs) based on 2D materials hold great promise for ultracompact polarimeters due to their ability to directly detect polarization states. However, the existing PPDs based on 2D materials tend to focus on a single metric, making it challenging to obtain both a large polarization ratio (PR) and high responsivity (R). Here, black phosphorus (BP) PPDs are proposed under a nanowire configuration that enables large PR and high R simultaneously. Benefitting from the anisotropic coupling between the BP crystal and the nanowire geometry, specific light‐field distributions are formed under orthogonally polarized light incidences, through selectively exciting the localized surface plasmon and leaky‐mode resonances. A large carrier concentration gradient inherent to this structure is formed to induce a high response contrast and a large Dember current, enabling an ultrahigh PR ≈ 118.4, R ≈ 802.42 A W−1, and ultrashort response time ≈ 636 ps. Finally, a key‐free optical encryption communication system is constructed, demonstrating one of its promising applications.

Hemoglobin alpha is a redox-sensitive mitochondrial-related protein in T-lymphocytes

Hemoglobin subunits, which form the well-characterized, tetrameric, oxygen-carrying protein, have recently been described to be expressed in various non-canonical cell types. However, the exact function of hemoglobin subunits within these cells remains to be fully elucidated. Herein, we report for the first time, the expression of hemoglobin alpha-a1 (Hba-a1) in T-lymphocytes and describe its role as a mitochondrial-associated antioxidant. Within naïve T-lymphocytes, Hba-a1 mRNA and HBA protein are present and highly induced by redox perturbations, particularly those arising from the mitochondria. Additionally, preliminary data using a T-lymphocyte specific Hba-a1 knock-out mouse model indicated that the loss of Hba-a1 led to an exacerbated production of mitochondrial reactive oxygen species and inflammatory cytokines after a stress challenge, further supporting the role of HBA acting to buffer the mitochondrial redox environment. Interestingly, we observed Hba-a1 expression to be significantly upregulated or downregulated depending on T-lymphocyte polarization and metabolic state, which appeared to be controlled by both transcriptional regulation and chromatin remodeling. Altogether, these data suggest Hba-a1 may function as a crucial mitochondrial-associated antioxidant and appears to possess critical and complex functions related to T-lymphocyte activation and differentiation.

Three-dimensional displacement measurement based on DIC-assisted polarization fringe projection

Digital image correlation (DIC)-assisted fringe projection profilometry (FPP) is a recently developed method for measuring the shape and displacement of complex structures. However, FPP only requires the fringe pattern on the object surface while DIC only requires the texture pattern on the object surface. Therefore, separating high-quality fringe patterns and texture patterns has always been a research difficulty. In this paper, a texture-separable polarization phase-shift coding strategy (TSPP) is proposed to superimpose the phase-shift pattern of the horizontal polarization state and the white light texture pattern of the vertical polarization state into a new phase-shift fringe. Since the polarization states in two orthogonal directions do not affect each other, the texture pattern on the surface of the object can be obtained while projecting the phase-shifted fringes. Our proposed method can separate fringe patterns and texture patterns in real time without the need for additional hardware equipment, and can cope with different lighting environments to obtain high-quality fringe and texture patterns. Experimental results show that the proposed method can obtain better three-dimensional reconstruction effects and displacement measurement results.