Orthogonal Polarization Research Articles

Climatology and trends of cirrus geometrical and optical properties in the Amazon region from 7-yr of CALIPSO observations

Recent studies have shown that the presence of cirrus clouds in the Amazon is higher than in other tropical regions, but also that convective activity in the region is decreasing, which could mean a decrease in high clouds. We used data from 2009 to 2016 from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), aboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), to study cirrus over the Amazon. Here we report on an analysis of the frequency of occurrence, base and top altitude, geometric thickness, and optical depth for the whole Amazon, as well as their spatial distribution and medium-term trends. A total of 1,473,863 vertical profiles were analyzed containing 728,123 cirrus layers, being 37.0% in the wet and 21.2% in the dry season. They are evenly distributed throughout the region during the wet season and concentrated in the northwest of the Amazon during the dry season. In terms of cloud optical depth (COD), most cirrus were optically thin (0.03<COD<0.3), with a relative frequency of 43.9%, while subvisual (COD<0.03) and thick (COD>0.3) corresponded to 22.0 and 34.1%, respectively. The results indicate a significant reduction in the frequency of cirrus occurrence of 1.3 ± 0.3% per year in the wet season, accompanied by a reduction of the geometric thickness of the thickest cirrus by 57 ± 18 m. This corroborates previous reports of a reduction of convective activity and high cloud fraction in the region.

Metasurface-Based Optical Logic Operators Driven by Diffractive Neural Networks.

In this paper, a novel optical logic operator based on the multifunctional metasurface driven by all-optical diffractive neural network is reported, which can perform four principal quantum logic operations (Pauli-X, Pauli-Y, Pauli-Z, and Hadamard gates). The two ground states and are characterized by two orthogonal linear polarization states. The proposed spatial- and polarization-multiplexed all-optical diffractive neural network only contains a hidden layer physically mapped as a metasurface with simple and compact unit cells, which dramatically reduces the volume and computing resources required for the system. The designed optical quantum operator is proven to achieve high fidelities for all four quantum logical gates, up to 99.96% numerically and 99.88% experimentally. The solution will facilitate the construction of large-scale optical quantum computing systems and scalable optical quantum devices.

Breaking symmetry restriction of chirality through spin-decoupled phase modulation utilizing non-mirror-symmetric meta-atoms.

The geometric phase in metasurfaces follows a symmetry restriction of chirality, which dictates that the phases of two orthogonal circularly polarized waves are identical but have opposite signs. In this study, we propose a general mechanism to disrupt this symmetric restriction on the chirality of orthogonal circular polarizations by introducing mirror-symmetry-breaking meta-atoms. This mechanism introduces a new degree of freedom in spin-decoupled phase modulation without necessitating the rotation of the meta-atom. To demonstrate the feasibility of this concept, we design what we believe is a novel meta-atom with a QR-code structure and successfully showcase circular-polarization multiplexing metasurface holography. Our investigation offers what we believe to be a novel understanding of the chirality in geometric phase within the realm of nanophotonics. Moreover, it paves the way for the development of what we believe will be novel design methodologies for electromagnetic structures, enabling applications in arbitrary wavefront engineering.

Dual-band transmissive linear to circular polarization converter with angular-stable and orthogonal polarizations

Abstract A dual-band angular-stable transmissive linear to circular polarization converter based on metasurface is proposed and demonstrated in this work. The converter consists of three layers. The top and bottom layers are formed by an array of double split-ring layers. The unit cell of the central layer contains a square loop nesting a slant dipole. The split-rings create two resonances, enabling dual-band operation. The slant dipole and square loop are useful for improving the quality of circular polarization conversion. It is shown that the proposed polarization converter converts the incident linearly polarized wave into circularly polarized wave with opposite polarization modes over the frequency ranges of 8.77–10.58 and 17.59–19.88 GHz. The angular stability is up to 60° for 3 dB axial ratio. Moreover, the thickness of unit cell has a wavelength below 0.06 at the lower band. Compared with other designs in the literature, the structure bears merits of wideband response, high angular stability, and low-profile property within dual-band operational region. To validate the design, a sample prototype was designed, fabricated, and measured. The measured results are in good agreement with the simulated ones.

Magnetic-electric dipole circularly polarized antenna with unidirectional radiation pattern with improved characteristics

Abstract In this paper, a compact unidirectional antenna consisting of a planar electric dipole and a shortened connecting element is introduced. This antenna is excited by a Γ-shaped feeding line. A wide impedance bandwidth in the frequency range of 1.3–3.3 GHz is observed in the output performance. Sufficient main lobe and low level back lobe have been introduced as other characteristics of the structure, based on radiation patterns. The antenna design process is evaluated step-by-step and using parametric study based on the antenna geometry. One of the main features of the desired antenna is the realization of circular polarization in a high percentage of the operational bandwidth 1.5–3.3 GHz. The radiation patterns of the orthogonal planes E-field and H-field along with the left-handed and right-handed circular polarization patterns for the desired antenna have been extracted and analyzed. A three-dimensional structure in the form of stacked stepped disks (SSD) is introduced to increase overall performance of antenna. There is an acceptable similarity between the E-field and H-field page patterns, which shows the accuracy of the design process. On the other hand, for studying the circular polarization, left-handed and right-handed patterns based on the main beam direction and orthogonal polarization level have acceptable performance. The maximum overall gain of the antenna in the designed frequency band is near to 13 dB.

Ultrafast Visible/Near‐Infrared Dual‐Band Selective Optical Switching via Polarization Control in Layered Low‐Symmetry TlSe

AbstractDual‐band optical signals, consisting of visible and infrared wavelengths, hold significant potential in various fields such as night vision, vehicle safety, bioimaging, and optical communications. Consequently, considerable attention has focused on modulation techniques for visible‐infrared dual‐band signals, including various electrochromic devices. However, these devices often suffer from low speeds and complex structures, making them unsuitable for satisfying the current demand for ultrafast on‐chip nanophotonics. Here, an ultrafast, dual‐band selective optical switching is presented in thallium selenide (TlSe), a layered nanomaterial with low‐symmetry. Transient absorption microscopy directly reveals distinct modulation bands in the visible and near‐infrared (NIR) regions. Notably, these bands exhibit orthogonal polarization dependencies, enabling the selective modulation of visible and NIR light via polarization control. Theoretical analysis reveals that the modulation bands in the visible and NIR regions arise from the perpendicularly anisotropic excited‐state absorption of electrons and holes, respectively. This is supported by distinct ultrafast cooling times observed for electrons and holes. The modulations exhibit picosecond‐scale dynamics owing to efficient Auger recombination. These exceptional characteristics highlight the promising nature of low‐symmetry TlSe as a novel material for ultrafast dual‐band nanophotonics. Furthermore, this work provides fundamental insights into anisotropic carrier dynamics, including effective mass‐dependent cooling and many‐body interactions.

Improving resolution in two orthogonal orientations from a single-shot digital holographic microscopy

We demonstrate a single-shot digital holographic microscopy technique to improve the diffraction-limited resolution in two orthogonal orientations simultaneously by dual-channel orthogonal polarization multiplexing approach. Orthogonally polarized two oblique beams are employed to illuminate the sample and two reference beams with mutually orthogonal polarization are interfered with the object beams in a custom-designed Mach–Zehnder configuration. This technique is potentially beneficial to encode high frequency sample information from two orthogonal directions simultaneously in a single recorded hologram where the high frequency spectra is synthesized by the selective spectral stitching. Thus, the resolution is enhanced along two orientations from a single-shot hologram in this work. Both the simulation and experimental results are shown for the proposed technique with around 2-fold resolution enhancement over the diffraction limit.

Real-time generation of underwater de-backscattering videos using the arrayed orthogonal polarization light source and active polarization imaging

Underwater active polarization imaging applications require mechanical rotate the analyzer to obtain orthogonal polarization state images, resulting in the inability to output the video in real time. The real-time generation of underwater de-backscattering videos using the arrayed orthogonal polarization light source and active polarization imaging method is proposed. First, the method replaces the orthogonal polarization switching position from the camera to the light source side, demonstrating that it does not affect the de-backscattering performance. Then, the arrayed orthogonal polarization light source is designed, consisting of two groups of LED lamp beads with orthogonal polarization states arranged in a staggered manner, outputting orthogonal polarization states light at different moments. The mechanical structure for polarization state switching is eliminated from the hardware, realizing an all-solid-state structure. Third, the synchronization device is designed to control the camera and the light source, realizing the acquisition of orthogonal polarization state images. Finally, the pipelined active polarization imaging method achieves real-time video output. Experimental results show the method can output the de-backscattering video in real time. The de-backscattering performance is close to the mechanical active polarization imaging, and the deviation degrees are less than 7%. The method has the advantages of easy implementation, high real-time performance, unaffected frame rate of the output video, and unlimited camera sensors.

Metasurface-driven polarization-division multiplexing of PCSEL for optical communications

Free-space optical communications hold promising advantages, including a large bandwidth, access to license-free spectrum, high data rates, quick and simple deployment, low power consumption, and relaxed quality requirements. Nevertheless, key technical challenges remain, such as a higher transmission efficiency, a lower transmission loss, and a smaller form factor of optical systems. Here, we demonstrate the viability of circular-polarization-multiplexed multi-channel optical communication using metasurfaces alongside a photonic-crystal surface-emitting laser (PCSEL) light source at wavelength of 940 nm. Through the light manipulation with metasurface, we split the linearly polarized incidence into left and right circular polarizations with desired diffraction angles. Such orthogonal polarization states provide a paradigm of polarization division multiplexing technique for light communication. The PCSEL light source maintains a low divergence angle of about 0.373 degrees after passing through an ultra-thin metasurface without further bulky collimator or light guide, making end-to-end (E2E) and device-to-device (D2D) communications available in a compact form. Both light source and modulated polarized light exhibit a − 3 dB bandwidth over 500 MHz, with successful 1 Gbit/s transmission demonstrated in eye diagrams. Our results affirm that metasurface effectively boosts transmission capacity without compromising the light source's inherent properties. Future metasurface designs could expand channel capacity, and its integration with PCSEL monolithically holds promise for reducing interface losses, thereby enhancing efficiency.

Depolarized Holography with Polarization-Multiplexing Metasurface

The evolution of computer-generated holography (CGH) algorithms has prompted significant improvements in the performances of holographic displays. Nonetheless, they start to encounter a limited degree of freedom in CGH optimization and physical constraints stemming from the coherent nature of holograms. To surpass the physical limitations, we consider polarization as a new degree of freedom by utilizing a novel optical platform called metasurface. Polarization-multiplexing metasurfaces enable incoherent-like behavior in holographic displays due to the mutual incoherence of orthogonal polarization states. We leverage this unique characteristic of a metasurface by integrating it into a holographic display and exploiting polarization diversity to bring an additional degree of freedom for CGH algorithms. To minimize the speckle noise while maximizing the image quality, we devise a fully differentiable optimization pipeline by taking into account the metasurface proxy model, thereby jointly optimizing spatial light modulator phase patterns and geometric parameters of metasurface nanostructures. We evaluate the metasurface-enabled depolarized holography through simulations and experiments, demonstrating its ability to reduce speckle noise and enhance image quality.

Ultracompact Single-Photon Sources of Linearly Polarized Vortex Beams.

Ultracompact chip-integrated single-photon sources of collimated beams with polarization-encoded states are crucial for integrated quantum technologies. However, most of currently available single-photon sources rely on external bulky optical components to shape the polarization and phase front of emitted photon beams. Efficient integration of quantum emitters with beam shaping and polarization encoding functionalities remains so far elusive. Here, ultracompact single-photon sources of linearly polarized vortex beams based on chip-integrated quantum emitter-coupled metasurfaces are presented, which are meticulously designed by fully exploiting the potential of nanobrick-arrayed metasurfaces. The authors first demonstrate on-chip single-photon generation of high-purity linearly polarized vortex beams with prescribed topological charges of 0, - 1, and +1. The multiplexing of single-photon emission channels with orthogonal linear polarizations carrying different topological charges are further realized and their entanglement is demonstarated. The work illustrates the potential and feasibility of ultracompact quantum emitter-coupled metasurfaces as a new quantum optics platform for realizing chip-integrated high-dimensional single-photon sources.

Pulse energy exchange of vector solitons in a fiber laser

The energy exchange between orthogonal polarization components is crucial for the build-up of vector solitons (VSs). Unlike previous observations of energy exchange in the frequency domain, our experiments analyzed pulse energy flows in the time domain. We provide evidence to demonstrate the influence of the four-wave mixing (FWM) and cross-phase modulation (XPM) effect on VSs build-up in passive mode-locked fiber lasers through a perspective of pulse energy exchange. The results indicate that the energy exchange of PRVS caused by FWM and XPM is stronger than that of PLVS. The liner energy exchange caused by the birefringence of fiber and PC influences the period of energy exchange. After stabilization, the intra-cavity energy evolution period is one roundtrip for PLVS while serval roundtrips for PRVS. In the future, we can achieve PLVS by adjusting the linear energy exchange through cavity birefringence, thereby meeting the industrial demand for stable and uniform pulse trains.

Spintronic terahertz polarization programmable system for information encoding

Terahertz (THz) wave as an important electromagnetic wave has been increasingly applied in wireless communication and imaging sensing technology. It has been an increasingly practical application. Ultra-high data rates in communication technology push toward a broadband, controllable polarization, and multiple transmission channels signal sources. Here, we propose a programmable polarization spintronics terahertz source (PP-STS), in which contains a controllable polarization spintronic THz emitter and a microcontroller unit. The PP-STS not only can generate THz waves with wide frequency bandwidth, but also has the function of switching the orthogonal linear polarization state of the generated THz waves flexibly. By coding the microcontroller unit, the designed PP-SPS can directly program the orthogonal linear polarization states as a series of information to transmit. To achieve the interconversions between digital codes and the THz polarization information, an optimum matching THz polarization beam splitter (THz-PBS) is also designed via simulations and experiments. The THz-PBS, as a decoder, can accurately split the transverse electric (TE) and transverse magnetic (TM) modes into two THz detectors. At last, a coding and decoding prototype system of spintronic THz polarization is built by integrating the PP-STS, the THz-PBS and two THz detectors. The send and receive information with high speed and accuracy are verified in this prototype system as well. We believe that our work takes THz applications for multiplexing communications one step further and sheds light on commercializing the PP-STS with exciting manufacturing lines for efficient and economical THz polarization technology.

Efficient angular dispersed high-order harmonic generation by dual laser pulses interacting with a solid target

High-order harmonics emitted from relativistic laser–solid interaction can be used as a bright extreme ultraviolet source. However, such a source usually has mixed frequencies along the emission direction. Through theoretical and numerical studies, we propose a scheme to realize monochromatic harmonic emission along individual directions by using dual laser pulses with orthogonal polarizations, where a relativistic P-polarized laser is used as a pump laser in combination with a moderate S-polarized laser as a seed laser. We find that harmonics of the S-polarized laser can be efficiently generated with several orders of magnitude enhancement and spontaneous angular dispersion depending on the harmonic order. Our scheme may be beneficial to future applications requiring monochromatic radiation along a specific direction or multi-chromatic radiations in different directions.

Integration of Sensing and Communication in a W-Band Fiber-Wireless Link Enabled by Electromagnetic Polarization Multiplexing

The coexistence needs of sensing and communication in millimeter-wave (mmW) bands have urgently driven the seamless integration of sensing and communication in the upcoming mmW era. However, the time-frequency competition between the two functions makes it difficult to accommodate both high sensing resolution and large communication capacity. In this paper, we have designed a W-band fiber-wireless link with the integrated sensing and communication functions enabled by electromagnetic polarization multiplexing. The ultra-wideband fiber-wireless link in W band is enabled by the asymmetrical single-sideband modulation along with the optical heterodyne up-conversion. The electromagnetic polarization multiplexing allocates the sensing and communication functions on two orthogonal electromagnetic polarizations, respectively. Thus, all time-frequency resources of the fiber-wireless link can simultaneously serve these two functions without any resource competition, contributing to an ultra-high spatial resolution and an ultra-large data capacity at the same time. Our experimental results show the spatial resolution of up to 15 mm and data rate as high as 92 Gbit/s were simultaneously realized in W band after delivering over a 10.8-m wireless distance. The overall improvement of both the sensing and communication performance, to the best of our knowledge, led to a record capacity-resolution quotient of 61.333 Gbit/s/cm. In addition, we have qualitatively investigated the integrated sensing and communication fiber-wireless link, in terms of the carrier frequency, system bandwidth, multi-mmW access, and electromagnetic polarization crosstalk.

Localized spin-selective interference assisted broadband tunable chirality with diatomic all-dielectric metasurfaces

Chiral metasurfaces with spin-selective properties have shown an unprecedented ability to modulate optical properties on the subwavelength scale. Alternatively, the simultaneous implementation of broadband tunable chiral response and wavefront manipulation on minimalistically constructed monolayer metasurfaces can lead to a plethora of applications such as optical converter diodes, chiral imaging, and sensing. Benefiting from a localized interference between two pairs of achiral meta-atoms whose optical behavior is similar to that of a half-wave plate (HWP), we theoretically provide a design strategy for constructing meta-molecules for asymmetric transmission (AT) parameters using interference mechanisms, each of which achieves a specific modulation function in the terahertz (THz) band. Localized interference effects with polarization-selective properties permit the incident circular polarization to be transformed into its orthogonal polarization mode. Benefiting from spin-selective transmission, the proposed metasurface simultaneously implements polarization filtering and wavefront manipulation with the assistance of a geometric phase mechanism. Not only that, chiral imaging schemes are also evaluated under such a design mechanism. As a result, this generalized assembly scheme can not only be extended to arbitrary working bands, but also find a variety of applications in photodetectors.

Crosstalk-Free MIMO VLC Using Two Orthogonal Polarizations Multiplexed Large FOV Fluorescent Antennas

Crosstalk-Free MIMO VLC Using Two Orthogonal Polarizations Multiplexed Large FOV Fluorescent Antennas

Polarization-stable single-mode 795 nm grating-coupled surface-emitting laser for quantum sensing

We demonstrate a polarization-stable and single-mode grating-coupled surface-emitting laser (GCSEL) with high side-mode suppression ratio (SMSR) of ∼40 dB and orthogonal polarization suppression ratio (OPSR) of ∼25 dB around 795 nm. The fabricated devices have low threshold current of ∼4.8 mA and low electrical resistance of 53 Ω at 25 °C. Meanwhile, a low thermal resistance of ∼1 K/mW is achieved, which is comparable with that of the record of ever reported for vertical-cavity surface-emitting lasers (VCSELs). The far-field divergence angle of surface-emitting beam is ∼14.5°x14.7° at an injection current of 12 mA indicating a relatively good beam quality. Our results open what we believe is a new way to produce polarization-stable single-mode surface-emitting lasers with simple fabrication process. While the GCSEL is specifically designed for quantum sensing applications such as atomic clocks, magnetometers, and gyroscope, its performance in terms of low-power consumption, low thermal resistance, good beam qualities, and wafer-level testing are of particular interest for a wide range of applications.

Reflection-type surface lattice resonances in all-metal metasurfaces for refractive index sensing

Surface lattice resonance (SLR) is a pretty effective mechanism to realize ultranarrow linewidths in the spectrum. Herein, we propose and demonstrate reflection-type SLRs in all-metal metasurfaces experimentally, compared with the traditional transmission-type SLR, which can avoid the refractive index (RI) mismatch problem and are more suitable for high-efficiency RI sensing due to direct contact and strong light–matter interaction. The measured SLR linewidth is 13.5 nm influenced by the meta-atom size, which needs a compromise design to keep a balance between the narrow linewidth and noise immunity. Notably, the SLR sensitivity is determined by the lattice period along the polarization direction with regularity, which establishes an intuitive link between structures and optical responses and provides a theoretical guide for metasurface designs. Additionally, incident angle multiplexing will make the resonance wavelength red shift or blue shift in the case of orthogonal polarization. The rectangular array metasurface can realize dual SLRs with different sensing performances. Flexibly, the SLR can also be formed by the different meta-atoms and arrays. This research supports SLR multifarious applications involving not only RI sensing but also nonlinear optics, nano-lasers, etc.

High-Resolution Metalens Imaging Polarimetry.

Imaging polarimeters find many critical applications in applications ranging from remote sensing to biological detection. Metasurfaces have been proposed as a compact approach for imaging polarimeters, but prior strategies suffer from low imaging resolution. Here, we propose an interleaved metalens configuration for polarization imaging where three-row metasurface units within a group individually interact with three pairs of orthogonal polarization channels. The optical paths between the object and adjacent three-row metasurfaces are nearly equal, allowing the construction of a metalens polarimeter with an unlimited numerical aperture (NA), which is beneficial for high-resolution polarization imaging. The metalens polarimeter fabricated by crystalline silicon nanostructures has a NA of 0.51 at 632.8 nm and achieves an imaging resolution of up to a 1.2-fold wavelength. Polarimetric microscopy experiments demonstrate that metalens polarimeters can realize high-resolution polarization imaging for various microscopic samples. This study offers a promising solution for high-resolution metasurface polarization imaging, with the potential for widespread applications.