Polarization Sensitivity Research Articles

Polarization Independent Dynamic Beam Steering based on Liquid Crystal Integrated Metasurface

Digital Micromirror Devices, extensively employed in projection displays offer rapid, polarization-independent beam steering. However, they are constrained by microelectromechanical system limitations, resulting in reduced resolution, limited beam steering angle and poor stability, which hinder further performance optimization. Liquid Crystal on Silicon technology, employing liquid crystal (LC) and silicon chip technology, with properties of high resolution, high contrast and good stability. Nevertheless, its polarization-dependent issues lead to complex system and low efficiency in device applications. This paper introduces a hybrid integration of metallic metasurface with nematic LC, facilitating a polarization-independent beam steering device capable of large-angle deflections. Employing principles of geometrical phase and plasmonic resonances, the metallic metasurface, coupled with an electronically controlled LC, allows for dynamic adjustment, achieving a maximum deflection of ± 27.1°. Additionally, the integration of an LC-infused dielectric grating for dynamic phase modulation and the metasurface for polarization conversion ensures uniform modulation effects across all polarizations within the device. We verify the device’s large-angle beam deflection capability and polarization insensitivity effect in simulations and propose an optimization scheme to cope with the low efficiency of individual diffraction stages.

Polarization-selective dual-band infrared metamaterial perfect absorber

Abstract Metamaterial absorbers have significant effects and great potential for applications in a variety of important sciences and technologies, including infrared imaging, thermal emitters, electromagnetic shielding, and photodetectors. However, conventional absorbers with a single function are difficult to meet the growing demand of devices, especially for the situations where the absorption and polarization are simultaneously required in infrared detection. If the polarization absorption function is realized by integrating absorption and polarization elements, it will lead to a large overall system size and slow response time. To solve this problem, we propose a dual-band polarization-selective metamaterial perfect absorber, whose maximum absorptions at resonant wavelengths of λ1=2.824μm and λ2=7.622μm are 99.99% and 99.88%, respectively. The absorber exhibits strong polarization sensitivity, absorbing TM-polarized incident light and reflecting TE-polarized incident light at the two resonant wavelengths. The extinction ratios of the absorber at the two referred resonant wavelengths are 90.9 and 142.7, respectively. The proposed absorber would be beneficial for infrared polarization detection and imaging.

Metal-free ultrathin terahertz absorber with independently tunable dual narrow bands

Abstract A technique is introduced to precisely control the resonance behaviour of a metal-free graphene-based terahertz absorber by independently tuning dual resonant peaks. The proposed ultrathin absorber features a multilayer configuration, with two isolated resonator layers of patterned graphene on dielectric (SiO2) substrates, and a thin graphite sheet at the bottom serving as a reflector. The stacked arrangement enables independent tunability of the high-absorptivity resonant peaks at 7.33THz and 9.34THz. The structure, with a thickness of just λ/15 of the free-space wavelength, offers a compact design suitable for space-constrained applications. Its symmetrical geometry ensures polarization insensitivity and stable performance for incident angles up to 60°. Simulated results, analysed via CST Studio and validated with an Equivalent Circuit Model (ECM), demonstrate excellent thermal stability. Furthermore, the narrowband response of the proposed absorber improves its sensitivity for refractive index variations induced by biomolecular interactions validating its suitability in biosensing applications. The absorber demonstrates peak absorption across both the resonant frequencies with an analyte optimised at 1.5μm thickness. Sensitivity levels of 1.1THz/RIU and 1.05THz/RIU along with figure-of-merit (FOM) values of 2.11 and 2.23. are recorded for the lower and upper bands, respectively. The absorber offers enhanced selectivity owing to low values of full-width at half maximum (FWHM). High Q-factors of 12.85 and 19.3, confirm its strong potential for refractive index sensing. 

Multi-band and polarization-insensitive electromagnetically-induced transparency based on coupled-resonators in a metamaterial operating at GHz frequencies

The analogy of electromagnetically-induced transparency (EIT) has emerged as an intriguing phenomenon in metamaterials research, enabling precise control over electromagnetic wave propagation. In this work, a metamaterial is investigated to achieve polarization-insensitive and multi-band transparency in microwave region. The metamaterial unit-cell consists of three coupled resonators, engineered to exhibit distinct resonance frequencies within the GHz spectrum and their coupling results in transparency windows. The functionality of the metamaterial is validated experimentally, demonstrating dual-band transparency windows at 4.6 and 6.4 GHz. Additionally, under oblique incidence, a third transparency peak arises, and the achieved triple-band EIT peaks can be maintained above 67% up to an incident angle of 60°. Our work contributes a metamaterial platform offering multi-band EIT behavior and polarization insensitivity at GHz frequencies. The proposed structural design leverages coupled-resonator configurations to achieve enhanced control over electromagnetic wave propagation, promising significant advancements in both fundamental research and practical applications. These include advanced signal processing, high-efficiency filters, and sensors operating in GHz communication and radar systems.

Metamaterial-Based Radar-Infrared Camouflage Material for Building Insulation: Design and Performance Analysis

This study introduces a metamaterial microwave absorber (MMA)-lightweight envelope (LE), which is an innovative solution for integrating electromagnetic and infrared-compatible camouflage technologies into building structures. Specifically, MMA-LE incorporates a MMA into building designs for microwave/infrared-compatible camouflage. This study evaluated the microwave absorption performance, infrared camouflage capabilities, and energy-saving effects of MMA-LEs by analyzing the microwave absorption characteristics using the impedance matching theory and simulation software. A coupled heat and moisture transfer model was used to assess isothermal moisture absorption, heat transfer coefficients, and annual heating/cooling loads. Furthermore, infrared imaging tests verified the effectiveness of the camouflage. Two MMA-LE designs (single and double absorber layers) achieve over 90% microwave absorption in the 3.2–11.2 GHz and 1.85–12.67 GHz frequency ranges with relative bandwidths of 111.1% and 149%, respectively, and with polarization insensitivity. Moreover, the MMA-LE enhanced the wall heat and moisture transfer performance, reduced the relative humidity, and reduced the thermal load under Guangzhou's climate conditions. However, despite the improved moisture resistance, the double-layer MMA-LE increased the envelope moisture content, thus reducing thermal insulation. In addition, the limited absorbency of the substrate material results in a modest increase in the dielectric constant, consequently decreasing the resonant frequency of the hybrid structure compared to dry samples. Nevertheless, the thermal insulation properties of MMA-LEs effectively insulate the internal heat sources, achieving optimal infrared camouflage. In conclusion, this study provides a novel solution for microwave-infrared-compatible camouflage in building applications, offering significant theoretical and practical value.

Theoretical study of a triple-band tunable terahertz metamaterial absorber with polarization insensitive and high refractive index sensing based on bulk Dirac semimetal

In this paper, a triple-band metamaterial absorber in the terahertz frequencies is proposed, and its refractive index sensing characteristics are analyzed, where the bulk Dirac semimetal (BDS) periodic array is on top of a photonic crystal slab backed with a metal ground plane. The simulation results show that the absorber achieves three perfect absorption peaks in the range of 3.4–5.2 THz, whose absorption rates are over 96%, and a maximum quality factor (Q) of 74.1. The designed absorber exhibits excellent polarization insensitivity and dynamic tunability; further, the tuning of the Fermi energy level of BDS enables the dynamic adjustment of absorption frequencies and absorption rates of these peaks. By analyzing the distributions of the electromagnetic field and different structural parameters, it is revealed that the absorber mainly dissipates the electromagnetic wave through coupled resonance and localized surface plasmon resonance (LSPR) effects to achieve perfect absorption. Further, the metamaterial absorber shows the capacity to detect analytes with varying refractive indices, and the absorber has a maximum sensitivity S of 405 GHz/RIU with high detection accuracy. This work provides novel design options for triple-band terahertz metamaterial absorbers and their potential applications in refractive index sensing.

Broadband Solar Absorber and Thermal Emitter Based on Single-Layer Molybdenum Disulfide.

In recent years, solar energy has become popular because of its clean and renewable properties. Meanwhile, two-dimensional materials have become a new favorite in scientific research due to their unique physicochemical properties. Among them, monolayer molybdenum disulfide (MoS2), as an outstanding representative of transition metal sulfides, is a hot research topic after graphene. Therefore, we have conducted an in-depth theoretical study and design simulation using the finite-difference method in time domain (FDTD) for a solar absorber based on the two-dimensional material MoS2. In this paper, a broadband solar absorber and thermal emitter based on a single layer of molybdenum disulfide is designed. It is shown that the broadband absorption of the absorber is mainly due to the propagating plasma resonance on the metal surface of the patterned layer and the localized surface plasma resonance excited in the adjacent patterned air cavity. The research results show that the designed structure boasts an exceptional broadband performance, achieving an ultra-wide spectral range spanning 2040 nm, with an overall absorption efficiency exceeding 90%. Notably, it maintains an average absorption rate of 94.61% across its spectrum, and in a narrow bandwidth centered at 303 nm, it demonstrates a near-unity absorption rate, surpassing 99%, underscoring its remarkable absorptive capabilities. The weighted average absorption rate of the whole wavelength range (280 nm-2500 nm) at AM1.5 is above 95.03%, and even at the extreme temperature of up to 1500 K, its heat radiation efficiency is high. Furthermore, the solar absorber in question exhibits polarization insensitivity, ensuring its performance is not influenced by the orientation of incident light. These advantages can enable our absorber to be widely used in solar thermal photovoltaics and other fields and provide new ideas for broadband absorbers based on two-dimensional materials.

Ultra-wideband solar absorber via vertically structured GDPT metamaterials

We explore a new solar absorber via vertically structured metamaterials integrating 2D graphene, dielectric layers of silica (SiO2), aluminum oxide (Al2O3), and phase-transition vanadium dioxide (VO2) graphene, dielectric, phase transition (GDPT), achieving broadband absorption and polarization independence. Applying the finite-difference time-domain (FDTD) method, the optical performance of the absorber is analyzed under the normal incidence of a plane wave spanning wavelengths from 250 to 4000 nm. Particularly, our investigation reveals a broad bandwidth exceeding 90 % absorption, spanning 3559 nm from 250 to 3809 nm, with an impressive average absorption efficiency of over 95.9 %. Significantly, the absorber demonstrates polarization independence and insensitivity to large angles of incidence, enhancing its practical capability. We illuminate the important role of Fabry-Perot resonance in absorption by precisely tuning layer thicknesses to induce interference effects. The integration of graphene, dielectric layers, and VO2, augmented by Fabry-Perot resonance, provides a vital foundation for high-performance solar energy conversion technology. This technology has important applications in efficient and broadband solar absorbers, and these absorbers can maintain high performance under different conditions. Our goal is to solve current technological challenges and contribute to the development of next-generation solar energy conversion for various photon technologies, such as energy harvesting, electromagnetic wave capture, and photovoltaic devices.

Graphene-Based Dual-Band Metasurface Absorber with High Frequency Ratio.

In this paper, we propose a novel dual-band metasurface absorber with a high frequency ratio based on graphene. By carefully designing a centrally symmetrical graphene pattern and positioning it on a glass medium, while utilizing ITO as a ground, the metasurface absorber achieves remarkable high frequency ratio microwave absorption. Specifically, this metasurface absorber exhibits two distinct resonance points at 3.7 GHz and 14 GHz, with an impressive frequency ratio over 3.5. It achieves over 90% absorption efficiency in the frequency ranges of 3.5-4.5 GHz and 13.5-14.5 GHz, highlighting its capability to effectively absorb microwaves across widely spaced frequency bands. Furthermore, the metasurface absorber demonstrates optical transparency and polarization insensitivity, adding to its versatility and potential applications. The measured results of the fabricated prototype validate its design and potential for practical use.

The Correction Method for Wavefront Aberration Caused by Spectrum-Splitting Filters in Multi-Modal Optical Imaging System

In current biomedical and environmental detection, multi-modal optical imaging technology is playing an increasingly important role. By utilizing information from dimensions such as spectra and polarization, it reflects the detailed characteristics and material properties of the targets. However, as detection system performance becomes more complex, issues such as aberrations introduced by multilayered lenses, signal attenuation, decreased polarization sensitivity, and latency can no longer be ignored. These factors directly affect the assessment of image details, influencing subsequent analyses. In this paper, we propose a method for designing and optimizing spectrum-splitting filters that considers the wavefront aberration and transmittance of the multi-modal optical imaging system. The method of optimizing coating phases to minimize scalar phase aberrations while maximizing system transmission leads to substantially improved imaging performance. Simulation and experimental results demonstrate that the method can improve the imaging performance. The proposed approach has potential applications in fields such as biomedical field, multi-spectral, remote sensing and microscopy.

A closely spaced dual band polarization insensitive FSS for 5G applications

This study presents a novel single layer Frequency Selective Surface (FSS) for fifth generation (5G) applications with a polarization independent closely spaced dual band response. The proposed design consists of four split ring apertures etched on a square patch printed on a RT5880 dielectric substrate. The FSS has two stop-bands at 24.78 GHz and 28 GHz center frequencies with attenuations around 55 dB. The S21<−10 dB bandwidths (BW) of these bands are 14.48 % and 9.25 %, respectively and these closely spaced bands succeed 1.13 frequency ratio. It shows a stable frequency response for both TE and TM polarizations. Furthermore, the FSS represents a single layered and quite thin (thickness 0.042λl) structure with its unit cell size (0.70λl × 0.70λl, where λl is the free-space wavelength at lower frequency). The novelty of the presented FSS is not only achieving a small closely spaced band ratio in the mmWave band and exhibiting polarization insensitivity but also providing these features with a simple geometry and, uncomplicated single layer structure. The simulation results were confirmed by well accordant measurement results. All these results make the presented FSS a good candidate for 5G electromagnetic interference (EMI) shielding applications.

Symmetric engineered central cross-shaped broadband metamaterial absorber with high absorption and stability for solar sailing and solar energy applications

We propose a theoretical design and analysis of a broadband metamaterial absorber (MMA) with significant potential for solar sailing applications which is a method of spacecraft propulsion that usages the momentum of sunlight to propel a spacecraft through space. The absorber features a metal-dielectric-metal configuration with a tungsten (W) based resonator and ground plane, and a Silicon-dioxide (SiO₂) substrate. Addressing the critical need for materials that can efficiently harness solar radiation for propulsion in space, our design achieves an average absorption of 99.15 % over a broad spectrum from 250 nm to 1200 nm, covering the UV–Visible–NIR regions, with near-unity absorption peaks at 362 nm and 915.8 nm. It maintains high absorptions of 84.9 % and 86 % under transvers electric and transvers magnetic modes respectively, demonstrating excellent wide incident angle stability and polarization insensitivity due to its symmetric design. PCR values close to zero confirm its functionality as an absorber rather than a polarizer. The MMA shows minimal deformation across temperatures from 500 K to 1750 K and remains stable under various mechanical stresses, proving its durability and efficiency in space. Additionally, in solar thermophotovoltaic (STPV) systems, the MMA demonstrates high photothermal conversion efficiency (PTCE) over a wide temperature range (500 °C to 1500 °C) and different concentration factors. This dual functionality highlights its potential for both efficient space exploration and terrestrial solar energy harvesting, making it a versatile tool for future technological applications.

Vector magnetometry employing a rotating RF field in a single-beam optically pumped magnetometer

Magnetic field vector information is crucial for many advanced applications, such as navigation and biomedical imaging. However, existing methods often lack high sensitivity or require complex setups. This study addresses these challenges by proposing a novel vector magnetometry method using a single-beam optically pumped magnetometer. A rotating radio-frequency field is innovatively utilized to excite atomic spin precession, enabling accurate measurement of the magnetic field direction based on scalar measurement. The method is tested through physical experiments with different magnetic field configurations to validate its performance. The experimental results demonstrate high accuracy, and achieve a magnetic field amplitude sensitivity of 800 fT/Hz1/2, an azimuth sensitivity of 100 μrad/Hz1/2, and a polar angle sensitivity of 13 μrad/Hz1/2. The proposed method facilitates sensor miniaturization and is suitable for applications in high magnetic field environments, such as geomagnetic field.

Polarized Upconversion of sub-100 nm Single Nanoparticles.

Upconversion nanoparticles are popular as imaging probes due to their advantages in photostability and controllable emission dimensions. However, upconversion polarization remains largely uncharted with previous reports limited to microstructures. In this work, we report the observation of polarized upconversion emissions from β-NaYF4 single nanostructures below 100 nm. At the sub-100 nm scale, nanorods, nanodiscs, and nanoplates exhibit distinctive polarization degrees despite the same doping concentrations of lanthanides. We find this varied polarization degree results from the crystallographic orientation of nanostructure in relation to the light field and can be linked to the distinctive emission spectrum profile with varied Stark splitting transition ratios from Er3+. Our findings provide a comprehensive understanding of the polarization properties of upconversion nanoparticles, revealing a previously unexplored aspect of light emission. This discovery expands our knowledge of upconversion nanoparticles and also opens new possibilities for their use in future imaging and sensing applications, where polarization sensitivity is crucial.

Imidazo[1,2-α]pyridine-based polarity and viscosity-dependent fluorescent probes and application in selective detection of 2,6-dichloro-4-nitroaniline

Three novel organic fluorescent probes M1-M3 with different conjugation length have been designed and synthesized from readily available starting materials via concise procedures. The obtained carbonyl-substituted imidazopyridines M1-M3 exhibit viscosity- and polarity-dependent dual-responsive properties. Structural modulation indicates that the polarity and viscosity sensitivity of M1-M3 can be tuned by variation of conjugation length. Importantly, M1-M3 demonstrate sensing ability for 2,6-dichloro-4-nitroaniline (DCN) with high selectivity and sensitivity in THF with a limit of detection (LOD) of 189 ppb, 62 ppb, and 54 ppb, respectively. The luminescence quenching of the compounds is caused by photo-induced electron transfer.

All-in-One 2D Molecular Crystal Optoelectronic Synapse for Polarization-Sensitive Neuromorphic Visual System.

Neuromorphic visual systems (NVSs) hold the potential to not only preserve but also enhance human visual capabilities. One such augmentation lies in harnessing polarization information from light reflected or scattered off surfaces like bees, which can disclose unique characteristics imperceptible to the human eyes. While creating polarization-sensitive optoelectronic synapses presents an intriguing avenue for equipping NVS with this capability, integrating functions like polarization sensitivity, photodetection, and synaptic operations into a singular device has proven challenging. This integration typically necessitates distinct functional components for each performance metric, leading to intricate fabrication processes and constraining overall performance. Herein, a pioneering linear polarized light sensitive synaptic organic phototransistor (OPT) based on 2D molecular crystals (2DMCs) with highly integrated, all-in-one functionality, is demonstrated. By leveraging the superior crystallinity and molecular thinness of 2DMC, the synaptic OPT exhibits comprehensive superior performance, including a linear dichroic ratio up to 3.85, a high responsivity of 1.47 × 104 A W-1, and the adept emulation of biological synapse functions. A sophisticated application in noncontact fingerprint detection achieves a 99.8% recognition accuracy, further highlights its potential. The all-in-one 2DMC optoelectronic synapse for polarization-sensitive NVS marks a new era for intelligent perception systems.

Polarization-insensitive cross-polarization converter with high frequency selectivity based on an antenna-resonator-antenna module

In this paper, a novel transmission-type polarization-insensitive frequency selective polarization converter (PIFSPC) is proposed. The overall structural scheme of the proposed PIFSPC is based on an antenna-resonator-antenna (ARA) module, which is composed of a receiving patch antenna, double “S-shaped” half-wavelength resonators, and a transmitting patch antenna. By adopting cross-coupling, high frequency selectivity is achieved, and through the utilization of a staggered rotationally symmetric structure, polarization insensitivity is attained. The prototype possesses four transmission poles and two zeros on the polarization conversion spectrum, and it shows insensitivity to the polarization direction of incident electromagnetic waves. The frequency selectivity of the prototype at the lower and upper band edges is 425 dB/GHz and 283 dB/GHz respectively. The cross-polarization conversion rate (PCR) is over 95% within the passband from 4.93 GHz to 5.09 GHz for arbitrarily polarized azimuth incident waves, and its thickness is merely 0.052λ0. The operation bandwidth and frequency selectivity of the prototype can be readily altered. A prototype is fabricated and measured, with excellent consistency between simulations and experiments. It indicates the feasibility of integrating frequency selection and polarization conversion. The proposed PIFSPC has extensive application prospects in enhancing the anti-interference ability and electromagnetic compatibility in the fields of communication, measurement, and microwave detection.

Multimodal ultra-high Q-factor C2 asymmetric all-dielectric metasurface induced by quasi-BIC states

A high Q-factor resonant cavity indicates minimal energy loss at the resonance frequency. In this paper, we propose a four-leaf clover sensor with air pillars based on the all-dielectric metasurface and discuss the C2 asymmetric induced quasi-bound states in the continuum(quasi-BIC). Firstly, we obtain dual Fano resonance by C2 symmetric configuration. Secondly, by introducing C2 asymmetric parameters, leading to a new Fano resonance peak, and the Q-factor exceeds 104. Furthermore, When the incident laser changes from TE mode to TM mode, the original Fano resonance peaks gradually disappear, and a new peak is generated near the 1273 nm. The calculated polarization sensitivity is up to 0.012 per degree. The dynamic range (DR) of the peak value of transmission spectrum with polarization is 58 dB. By calculation, we have achieved a maximum sensitivity (S) of 270 nm/RIU for an optical refractive index sensor, with a figure of merit (FOM) value of 2250 RIU-1.

Polarization insensitive and wideband terahertz absorber using high-impedance resistive material of RuO2

This paper introduces a novel, cost-effective solution designed to achieve large absorption bandwidth within the THz spectrum employing a miniaturized, single-layer metamaterial structure. The designed structure features a single circular ring composed of an ohmic resistive sheet with notably higher sheet resistance than traditional metallic resonators. This distinctive design is implemented on a lossy dielectric polyimide substrate with a backing of metallic gold. Our developed absorbing structure demonstrates the capability to achieve a substantial absorption bandwidth ranging from 3.78 to 4.25 THz, maintaining a consistent absorption rate of over 90%. Moreover, we conducted an analysis to assess its absorption performance under various sheet resistance values within the top layer. Additionally, we characterized its angular stability and polarization insensitivity through oblique incident and polarization angle analysis. Finally, an RLC circuital and interference theory approach is adopted to justify its simulated results. The proposed absorber shows potential for a broad spectrum of applications, encompassing communication, imaging, and diverse integrated circuits operating within the THz band.

Sensitivity detection of imidacloprid pesticide using a metasurface sensor in THz spectrum regime

Imidacloprid (C9H10ClN5O2) pesticide is frequently used in agriculture as it effectively controls various insect pests. Accurate detection of imidacloprid concentrations is crucial for food safety and other fields. This work proposes a novel metasurface (MS) sensor with efficient sensitivity in the THz frequency regime to detect imidacloprid pesticides. The MS sensor has an electrical size of 7.17λ × 7.17λ with the smallest wavelength. The transmission coefficient remains stable for the metasurface sensor’s TE and TM polarization modes. Due to the symmetrical design, it exhibits strong electric and magnetic field enhancement with polarization insensitivity for different incident angles. The sensing capability is tested by implementing different sample analyte thicknesses of imidacloprid in the top surface of the MS sensor. Imidacloprid analyte thickness increases cause a red and blue change in the metasurface’s transmission frequency. The simulation results show that the suggested MS sensor has a refractive index (RI) sensitivity of 0.125 THz/RIU, and a Q factor of 5.262 and 4.084. This is a simple, cost-effective, sufficiently sensitive, and efficient THz MS sensor with a wide range of applications in pesticide concentration measurement, including imidacloprid.