Polarization Sensitivity Research Articles

Polarization independent perfect absorption of borophene metamaterials operating in the communication band

Two-dimensional (2D) materials, such as graphene and black phosphorus, support deeply confined and tunable plasmons, making them suitable for designing absorbers with ultra-compact size and flexible manipulation. However, the operating frequency of such plasmonic absorbers is difficult to control to the communication band. Here, we propose a metamaterials composed of a borophene array, a dielectric layer and a metal reflector to achieve an optical perfect absorber near the communication wavelength of 1550 nm. In order to overcome the polarization sensitivity caused by anisotropic borophene materials, another borophene layer is introduced to achieve a polarization independent absorber, which can be attributed to the fact that the energy of the electromagnetic field is transferred between two borophene arrays as the polarization angle changes. In addition, through the modulation of carrier density, it is feasible to fine-tune the resonance wavelength of the absorber to 1330 nm, which corresponds precisely to the second communication window. This work may provide a theoretical foundation for the development of polarization independent devices, potentially broadening the scope of their applications.

Two Varieties of Korean: Rightward Head Movement or Polarity Sensitivity?

A strong argument in favor of the existence of rightward, string-adjacent head movement comes from Han, Lidz, and Musolino (2007). They argue that Korean language-internal variation with respect to the scopal order between negation and universal quantifier objects shows that in the variety where negation takes wide scope, the negative marker must have moved along with the verb/auxiliary to the head of IP. This would then constitute evidence for rightward, string-adjacent head movement. In this article, I argue that this analysis actually makes different predictions than have been attested in Korean. Moreover, I argue that, following a well-known stand with respect to the nature of polarity sensitivity (Chierchia 2013), these facts follow naturally once it is assumed that in one variety, but not the other, universal quantifiers are positive polarity items. This makes the attested language-internal variation in Korean less exceptional since language-internal variation with respect to polarity sensitivity is widely attested.

Analysis of absorption and thermal radiation performance of solar absorbers based on TiN, Nb2O5 and graphene

This work proposes a multi-layer structured solar absorber based on TiN, metal oxide Nb2O5 and graphene. Simulations and calculations are based on finite-difference time-domain (FDTD) method. The average absorption efficiency of the structure is 94.41 % across the spectrum of 280–3000 nm, with absorption bandwidths of 2360 nm (for absorption efficiency exceeding 90 %) and 1819 nm (for absorption efficiency exceeding 95 %). Moreover, the weighted average absorption under AM 1.5 reaches 95.71 %, underscoring the exceptional absorption capabilities of the structure. This structure also has the property of polarization insensitivity. The absorption spectrum varies weakly with the polarization angle, and there is some deviation as the incident light increasing from 0 to 60°. However, the absorption efficiency at 60° is still 81.16 %. We further investigated the thermal radiation performance, discovering an efficiency exceeding 80 % within the range of 300–1400 K, and surpassing 90 % within 800–1400 K. These outstanding absorption and thermal radiation properties position the structure as highly versatile, with potential applications spanning solar energy harvesting and radiation-related fields.

High-Speed 2x1 Multiplexer with Carrier-Reservoir Semiconductor Optical Amplifiers

Leveraging the rapid carrier recovery times and minimal polarization sensitivity of carrier-reservoir semiconductor optical amplifiers (CR-SOAs), this study embeds them in a Mach–Zehnder interferometer (MZI) setup to emulate a 2x1 multiplexer (MUX) operating at 120 Gb/s. The focus is on incorporating AND logic gate functionalities into the CR-SOAs-based MZI structure to facilitate high-quality multiplexing. The proposed methodology utilizes the intrinsic gain and phase modulation capabilities of CR-SOAs-based MZI to effectively manipulate data streams. This innovative approach capitalizes on the unique properties of CR-SOAs, such as fast response times and low polarization sensitivity, to achieve optimal signal transmission quality and efficient multiplexing. To assess MUX performance, a quality factor metric is introduced as a comprehensive measure of signal integrity. Through exhaustive simulations and meticulous analysis, the study demonstrates the feasibility of achieving the desired data rate while maintaining superior signal transmission quality. The results underscore the efficacy of CR-SOAs-based MZI as versatile modules for high-speed multiplexing applications, offering unparalleled performance and efficiency. This research represents a significant advancement in understanding optical communication systems and provides valuable insights for optimizing signal quality and mitigating interference in practical real-world scenarios.

Fluorescence Lifetime Measurement For Studying Evaporation Of Bi-Component Droplet

Sprays are essential in engineering applications like evaporators and combustion chambers. Predicting the evaporation of multi-component liquid droplets is complex due to changing composition and properties. Measuring droplet composition is challenging, with limited non-intrusive methods available. Raman spectroscopy faces hurdles like weak signals and interference. Intensity based Laser-Induced Fluorescence (LIF) requires optical models to interpret data due to varying droplet size and position. Fluorescent dyes in liquid mixtures are sensitive to temperature, complicating measurements. Fluorescence lifetime measurements offer a promising alternative, being an absolute quantity less affected by reabsorption. This study develops a novel method using fluorescence lifetime to analyze droplet composition, leveraging Time-Correlated Single Photon Counting (TCSPC) for precise measurements. Factors such as dye concentration, solvent polarity, and temperature sensitivity are investigated. Calibration curves for ethanol-water mixtures correlate fluorescence lifetime with volume fraction. Experimental setups use TCSPC and femtosecond lasers for dye excitation. Results show that fluorescence lifetime decreases linearly with solvent polarity and is influenced by temperature and dye concentration. High dye concentrations cause self-quenching, altering temperature sensitivity. The method was applied to study the evaporation of ethanol-water droplets under acoustic levitation. Findings indicate that evaporation rates slow as the water fraction increases, with initial measurements showing higher water content due to partial evaporation. This research introduces a novel technique for droplet compositional analysis using fluorescence lifetime, providing insights into optimizing measurement accuracy and advancing understanding in engineering and related fields.

Broadband absorptive metamaterials enhanced by magnetic rubber to broaden bandwidth

A method to extend the operational bandwidth of metal-dielectric-metal (MDM) type absorptive metamaterials is proposed. An ultrathin, five-band absorptive metamaterial with wide-angle absorption and polarization sensitivity in the X-band is designed. The total absorption bandwidth across the five bands, with reflection losses below −10 dB (absorption rate greater than 90 %), is nearly 1 GHz. The physical mechanisms of absorption are analyzed through the distributions of surface current, electric field, and magnetic field. Samples were fabricated and tested, and the results were consistent with the simulation outcomes. To enhance the bandwidth of the absorptive metamaterial and its application prospects, magnetic materials such as barium ferrite and carbonyl iron were introduced into a rubber vulcanization layer, which was then combined with the ultrathin absorptive material to create a novel absorptive material. When the magnetic material content in the rubber layer was 50 wt%, the frequency range with reflection losses below −10 dB increased by approximately nine times, covering 69.5 % of the C-Ku band. This significantly broadens the bandwidth of the pure MDM-type absorptive metamaterial, providing a feasible solution for the design of broadband ultrathin absorptive materials.

Design and analysis of ultra-wideband miniaturized metamaterial absorbers for radiation suppression

This paper presents a novel miniaturized ultra-wideband metamaterial absorber with a thickness of 0.069λ L thick, engineered to suppress electromagnetic radiation in high-frequency chip packaging. The absorber’s bandwidth is enhanced through the incorporation of lumped resistors and patterned metal strips. Simulation results reveal an absorption efficiency exceeding 90% across the frequency range of 17.3–33.5 GHz, while maintaining polarization insensitivity and angular stability. The absorption mechanism is investigated using equivalent circuit theory and the S-parameter inversion method, which demonstrate consistent impedance matching and advantageous loss characteristics throughout the wide band. Relevant objects were meticulously prepared and tested, yielding a high correlation between the measured and simulated results. The proposed absorber, when integrated into package chips and patch antennas, significantly reduces the far-field electric field amplitude in both applications. Specifically, the packaged chip shows up to 19.7 dB of electromagnetic radiation suppression and the patch antenna structure achieves over 10 dB of radiation suppression in the 24.2 GHz–30.4 GHz range post-integration. These results affirm the absorber’s efficacy in effectively reducing unwanted electromagnetic radiation in specified frequency bands within complex electromagnetic environments. The absorber’s demonstrated effectiveness provides a promising approach to address the increasing issue of electromagnetic radiation in progressively miniaturized electronic devices.

Gate‐Modulated and Polarization‐Sensitive Photodetector Based on the MoS2/PdSe2 Out‐Of‐Plane Van Der Waals Heterostructure

AbstractPhotodetectors with good polarization detection ability are promising in many applications, such as remote sensing imaging and environmental monitoring. However, the traditional polarization detection systems fall short in meeting integration demands of the integrated‐circuits field due to additional optical elements. The emerging 2D materials with in‐plane anisotropic structures provide a possible method to fabricate remarkable polarization detectors. Modulating the band structure by gate voltage is an important strategy for developing optoelectronic devices. Herein, a polarized photodetector based on PdSe2/MoS2 out‐of‐plane heterojunction is fabricated. Due to its unique out‐of‐plane heterostructure, the device exhibits excellent photoresponse characteristics and polarization sensitivity, including an excellent responsivity of 10.19A/W, an extremely high external quantum efficiency of 2429%, a fast rise/decay time of 68/192 µs, and a high photocurrent anisotropy ratio of 3.09. Based on the adjustment of the built‐in electric field through gate voltage, the performance of the device can be accordingly modulated. As the gate voltage increases from −30 to 30 V, the responsivity gradually increases from 7.5 to 13A/W and the detectivity increases from 1.53 to 2.63 × 109Jones. Finally, its olarization imaging ability is demonstrated at different polarization angles. The findings indicate that PdSe2/MoS2 devices exhibit significant potential for polarized photoelectric detection.

Sensitivity of Polarization to Grain Shape. II. Aggregates

A previous study (Paper I) investigated the polarization properties of a variety of simple convex grain shapes, some of which were found to be consistent with the observed polarization properties of interstellar dust from far-ultraviolet to far-infrared. Here, we study the optical properties of 45 nonconvex shapes, all aggregates of N equal-sized spheres. We consider N = 2, N = 3, and N = 256 random aggregates obtained from three different aggregation schemes. We also consider “trimmed” N = 256 aggregates obtained by systematically trimming initially random aggregates to increase either flattening or elongation. The “macroporosities” of the studied aggregates range from Pmacro=0.18 (for the N = 2 bisphere) to Pmacro≈0.85 (for the N = 256 “BA” aggregates). The only aggregates consistent with observations of starlight polarization and polarized thermal emission are shapes that have been trimmed to increase their asymmetry. If interstellar grains are high-porosity aggregates, there must be processes causing extreme elongation or flattening; if not, interstellar grains must be dominated by fairly compact structures, with at most moderate porosities. The ratio of polarization in the 10 μm silicate feature to starlight polarization in the optical is shown to be insensitive to porosity and shape. X-ray scattering may be the best tool to determine the porosity of interstellar grains. We propose that modest porosities of interstellar grains could be the result of “photolytic densification.” High polarization fractions observed in some Class 0 cores require processes to reduce porosities and/or increase asymmetries of aggregates in dense regions.

Ultra Miniaturization and Transparency Frequency Selective Surface for Dual Band ISM Shielding

This article presents an ultraminiaturized frequency selective surface (FSS) for shielding 2.4 GHz and 5.8 GHz (ISM) signals. The unit cell size is 0.056λ × 0.056λ (λ is the free space wavelength at the first resonant frequency). It has smaller cell size and good transparency compared to previous ISM band studies, and transparency at 54%. The proposed FSS design consists of a wall structure and a compound square loop with 2.4 GHz and 5.8 GHz resonance frequencies for ISM band coverage. This FSS structure was fabricated on float glass with a dielectric constant of 8 by a photolithographic process. The fabricated FSS structure has excellent angular stability and polarization stability, which is further verified by experimentation. An easy optimization method is proposed to tune the independent resonant frequencies by optimizing the geometries individually. This FSS is interpreted by filtering through surface induced currents and equivalent circuit models. A prototype of the proposed FSS is fabricated and measured. The simulation results are in good agreement with the measured results. The proposed FSS has polarization insensitivity and 80∘ angle stability and is suitable for solving the EMI problem in ISM band.

A Low-profile Dual-band Frequency Selective Surface with High Selectivity at its Higher Passband

In order to meet the requirements for multiband communication, a dual-band passband frequency selective surface (FSS) with low-profile and high selectivity at its higher passband is proposed in this paper. The proposed FSS is a three-layer structure. An arc-cross patch (ACP) and four quarter-circular patches (QCP) are introduced on the outer layers to produce two transmission nulls of the higher passband, which result in high selectivity of higher passband. The inductively complementary structure on the middle layer is introduced to manipulate the coupling between layers which contribute to the low-profile and angular stability. The segmental study method is used to establish the equivalent circuit model (ECM) and analyze its mechanism. The proposed dual-band FSS, whose high selectivity was verified by experiment, is low-profile and shows good polarization insensitivity and angular stability. A feasible FSS design solution is provided for dual-band communication.

High Performance Balanced Linear Polarization Photodetector Based on 2D ReS2

AbstractConventional research on linear polarization photodetector for 2D materials has focused on the search for different anisotropic materials, combinations between materials, introducing plasmonic structures, and patterning 2D materials to improve performance. However, these methods provide limited improvement in polarization sensitivity. Here, a balanced photodetector structure is proposed that does not require an additional process and relies only on the presence of anisotropy in the material itself to substantially improve the polarization sensitivity. The balanced photodetector consists of two ReS2 photodetectors, where the single ReS2 photodetector exhibits excellent performance at 650 nm illumination, including a responsivity and detectivity of 0.28 A W−1 and 4.22 × 109 Jones. Benefiting from the anisotropy of ReS2, the single photodetector achieves excellent polarization sensitivity of 2.79 at 650 nm. The balanced photodetector system achieves an excellent performance of ≈20 dB linear polarization extinction ratio and 0.003° Hz−1/2 noise equivalent light polarization difference at 100 kHz. These performances can also be further optimized by adjusting the gate voltage. The results provide a basis for further development of high‐performance polarization photodetector for 2D materials.

Design of a Far-Infrared Broadband Metamaterial Absorber with High Absorption and Ultra-Broadband

We designed a metamaterial far-infrared absorber based on an MDM (metal–dielectric–metal) structure. We made a hollow crossed Ti microstructure at the top of the absorber. It is known that the coupling effect of equipartitional exciton resonance and intrinsic absorption at the surface of the depleting material has a strong influence on the absorber. Based on this, we investigated the absorption characteristics of the absorber using the Finite Difference in Time Domain (FDTD) theory. The results show that the absorber absorbed more than 90% of the light within a bandwidth of 12.01 μm. The absorber has an average absorption of 94.08% in the longwave infrared (LWIR) to ultra-longwave infrared (UWIR) bands (10.90–22.91 μm). The polarization insensitivity of the designed absorber is demonstrated by analyzing the absorption spectra of the absorber at different polarization angles. By adjusting the relevant geometric parameters, the absorption spectrum can be independently adjusted. Furthermore, the absorber exhibits good incidence angle insensitivity in both transverse electric (TE) and transverse magnetic (TM) modes. The absorbers are simple and easy to configure for applications such as optical cloaking, infrared heat emitters, and photodetectors. These advantages will greatly benefit the application of absorbers in practice.

Electromagnetically induced transparent bimodal to unimodal conversion realized by the nematic liquid crystal

In this paper, under the action of a gigahertz (GHz) band circularly polarized (CP) wave, a kind of CP metastructure (MS) is proposed. Recently, the nematic liquid crystal (NLC) has received great attention, but it is still difficult to realize the electromagnetically induced transparency (EIT) bimodal to unimodal under the control of NLC. Through the direct mutual coupling of the metal cross resonator, metal ring resonator, and dielectric cross resonator, modes coupling can be formed and generate transparent windows. Two different EIT states (unimodal and bimodal EIT) accompanied by slow light effects can be observed by regulating the NLC with the applied bias voltage (V bias). When the V bias is 0 V, two transparent windows can be achieved in the 6.595–8.443 GHz and 8.443–10.161 GHz bands. When V bias is 20 V, only one transparent window can be achieved in the 6.891–8.682 GHz band. Due to the high symmetry, the MS has the polarization insensitivity to CP waves. These extremely excellent properties make this MS have a wide application prospect. Noteworthy, the theoretical calculation result of EIT is verified by the two-oscillator theory model and circuit model, the results obtained are basically consistent with the simulation results.

Meta‐Optics Based Parallel Convolutional Processing for Neural Network Accelerator

AbstractConvolutional neural networks (CNNs) have shown great performance in computer vision tasks, from image classification to pattern recognition. However, superior performance arises at the expense of high computational costs, which restricts their employment in real‐time decision‐making applications. Computationally intensive convolutions can be offloaded to optical metasurfaces, enabling sub‐picosecond latency and nearly zero energy consumption, but the currently reported approaches require additional bulk optics and can only process polarized light, which limits their practical usages in integrated lightweight systems. To solve these challenges, a novel design of the metasurface‐based optical convolutional accelerator is experimentally demonstrated, offering an ultra‐compact volume of 0.016 , a low cross‐talk of ‐20 dB, polarization insensitivity, and is capable of implementing multiple convolution operations and extracting simultaneously various features from light‐encoded images. The ultra‐compact metasurface‐based optical accelerator can be compactly integrated with a digital imaging system to constitute an optical‐electronic hybrid CNN, which experimentally achieves a consistent accuracy of 96 % in arbitrarily polarized MNIST digits classification. The proposed ultra‐compact metasurface‐based optical convolutional accelerator paves the way for power‐efficient edge‐computing platforms for a range of machine vision applications.

Two-Dimensional GeS/SnSe2 Tunneling Photodiode with Bidirectional Photoresponse and High Polarization Sensitivity.

A two-dimensional (2D) broken-gap (type-III) p-n heterojunction has a unique charge transport mechanism because of nonoverlapping energy bands. In light of this, type-III band alignment can be used in tunneling field-effect transistors (TFETs) and Esaki diodes with tunable operation and low consumption by highlighting the advantages of tunneling mechanisms. In recent years, 2D tunneling photodiodes have gradually attracted attention for novel optoelectronic performance with a combination of strong light-matter interaction and tunable band alignment. However, an in-depth understanding of the tunneling mechanisms should be further investigated, especially for developing electronic and optoelectronic applications. Here, we report a type-III tunneling photodiode based on a 2D multilayered p-GeS/n+-SnSe2 heterostructure, which is first fabricated by the mechanical exfoliation and dry transfer method. Through the Simmons approximation, its various tunneling transport mechanisms dependent on bias and light are demonstrated as the origin of excellent bidirectional photoresponse performance. Moreover, compared to the traditional p-n photodiode, the device enables bidirectional photoresponse capability, including maximum responsivity values of 43 and 8.7 A/W at Vds = 1 and -1 V, respectively, with distinctive photoactive regions from the scanning photocurrent mapping. Noticeably, benefiting from the in-plane anisotropic structure of GeS, the device exhibits an enhanced photocurrent anisotropic ratio of 9, driven by the broader depletion region at Vds = -3 V under 635 nm irradiation. Above all, the results suggest that our designed architecture can be potentially applied to CMOS imaging sensors and polarization-sensitive photodetectors.

Target profiling of aroma compounds in three types of Japanese sake using solvent-assisted stir bar sorptive extraction with gas chromatography–mass spectrometry

Specially designated sake is a premium type of Japanese sake (rice wine), which meets the criteria for ingredients and production method, and is classified into three types: ginjo, junmai, and honjozo sake. This study aimed to characterize the aroma compounds of the three types using solvent-assisted stir bar sorptive extraction (SA-SBSE) with gas chromatography–mass spectrometry (GC–MS), which improved polar compound sensitivity compared with conventional SBSE. Multiple analyses by profiling of 27 commercial products, targeting 45 odor-active compounds detected using GC–olfactometry, showed characteristic compounds for each type. Through quantitative analysis, this study observed that junmai sake, with its complex aroma, contains several polar compounds, including vanillin, benzaldehyde, ethyl 2-hydroxy-4-methylvalerate, and 4-methyl-5,6-dihydropyran-2-one, indicating that these various polar compounds play a significant role in sake quality. Furthermore, target profiling for multiple samples using SA-SBES–GC–MS was first shown to be effective for elucidating the aroma characteristic of the beverage.

Programmable metasurfaces with high angular stability for arbitrarily-polarized obliquely-incident waves

Programmable metasurfaces show enormous potential in real-time electromagnetic (EM) manipulation and their stable responses to variable EM waves including incident angle and polarization changes are crucial for related applications. However, the demonstrated programmable metasurfaces are commonly considered in normal-incident waves with fixed polarization; how to achieve stable performance in more realistic scenarios of wide-angle and full-polarized wave incidences is still a challenge. Here, we propose and realize a wide-angle and full-polarization programmable metasurface, which can generate stabilized amplitude and phase responses at both transverse electric (TE) and transverse magnetic (TM) oblique incidences. These are achieved by introducing metallic walls around the metasurface element to reduce element coupling, which greatly improves the angular stability of its reflection responses. The mechanisms of angular insensitivity are analyzed comprehensively, and as a proof of concept, obliquely-incident beam steering, large-angle beam scanning and oblique vortex beam emitting are demonstrated on this programmable metasurface. Both the simulation and experimental results demonstrate that the programmable metasurface can operate well at both TE and TM wide-angle oblique incidences in the upper half space. Our work offers an actual route for improving the angular stability and polarization insensitivity of metasurfaces, which could push them one step closer towards more complicated applications.

Miura-ori based reconfigurable multilayer absorber for high-efficiency wide-angle absorption.

Radar stealth structures that can achieve high-efficiency wide-angle absorption are key components of future military equipment. However, it is difficult for both planar and three-dimensional (3D) absorbers to achieve efficient absorption in a large incidence angle range. The multilayer reconfigurable absorber component based on Miura origami provides a unique solution. First, the multilayer origami absorber is parameterized in the simulation software. Each origami structure is covered with resistive films that fit the panels. Geometric constraints are satisfied among the multilayer structures. They support reconfigurability in the range of continuous states (as opposed to discrete states), which is conducive to finding the folded state with a more efficient absorption rate within the frequency band. Secondly, the designed structure does not require a specialized mechanically supported multilayer origami absorber. In addition, the equivalent analogue circuit method is used to analyze the efficient absorption of multilayer origami under oblique incidence. Finally, our proposed absorber satisfies the requirements of multiple absorption metrics: broadband, high efficiency, wide incidence angle, and polarization insensitivity. As the validation, we simulated and fabricated a double-layer origami absorber. Our proposed origami absorber can maintain an absorption rate of more than 90% for both transverse electric (TE) and transverse magnetic (TM) polarizations in the operating frequency band (5-20 GHz) over a wide range of incidence angles (0°-70°). When the incidence angle qinc = 40°, the double-layer origami absorber (q1 = 90°, α1 = 60°, and a2 = 75°) can achieve at least 10 dB reflection reduction of -18 dB and -20 dB in TE and TM modes, respectively. The proposed origami absorber provides a reference for the design of other absorbers.

Band Alignment Engineering in 2D Ferroelectric Van der Waals Heterostructures for All‐In‐One Optoelectronic Architecture

Abstract2D van der Waals (vdW) heterostructures consisting of vertically stacking atomically thin semiconductors with different band structures provide a flexible platform to design integrated electronic and optoelectronic devices with multi‐functionalities. However, the realization of device multifunctionality requires the heterostructures with tunable band alignments. Here an efficient strategy is proposed by constructing 2D vdW ferroelectric semiconductor heterostructures composed of atomically thin ferroelectrics and semiconductors to achieve this goal. These calculated results indicate that the local built‐in electric field derived from the ferroelectric polarization can effectively modulate the band alignment of the heterostructures, leading to 36 potential band‐alignment transition pathways. Using SnS/In2Se3 vdW heterostructure as a prototype example, a reversible switching from high‐resistance to low‐resistance state is demonstrated by the band‐alignment transition from type‐II to type‐III driven by ferroelecric polarization switching, consequently leading to giant tunneling electroresistance (TER) ratio as high as 1012%. Moreover, the heterostructure with the momentum‐space matching band structure and in‐plane anisotropy exhibits broadband photoresponse from near‐infrared to ultraviolet regions and excellent polarization sensitivity with the dichroic ratio up to 10.3. The ferroelectric polarization‐dependent conductance state and photoresponse in the heterostructures make them large potential for the realization of all‐in‐one optoelectronic architecture in artificial vision system.