Polarization Control Research Articles

Extension of Babinet’s relations to reflective metasurfaces: Application to the simultaneous control of wavefront and polarization

Extension of Babinet’s relations to reflective metasurfaces: Application to the simultaneous control of wavefront and polarization

Reconfigurable terahertz multifunctional wave plates with VO2/Ge hybrid metasurfaces.

Active control of polarization using metasurfaces is crucial in terahertz optics, offering promising advancements in sensing, imaging, and telecommunications. Here, we developed reconfigurable terahertz multifunctional wave plates by leveraging vanadium dioxide/germanium hybrid metasurfaces. This approach allows for mutual role changing of metasurface among quarter-wave plate, half-wave plate, and full-wave plate, facilitated by the introduction of continuous-wave and pulse lasers. The photoinduced phase change of vanadium dioxide, along with the bridging control of germanium, plays a key role in the transition of multifunctional wave plates. Also, the analysis of polarization conversion ratio, ellipticity, and underlying physics demonstrates the ability of multifunctional wave plates. These discoveries deliver valuable insight into advanced polarization control and demonstrate the potential for innovative active-control devices.

Full transmission of vectorial waves through 3D multiple-scattering media.

A striking prediction from the random matrix theory (RMT) in mesoscopic physics is the existence of "open channels": waves that use multipath interference to achieve perfect transmission across an opaque disordered medium even in the multiple-scattering regime. Realization of such open channels requires a coherent control of the complete incident wavefront and has only been achieved for scalar waves in two dimensions (2D) so far. Here, we utilize a recently proposed "augmented partial factorization" full-wave simulation method to compute the polarization-resolved scattering matrix from 3D vectorial Maxwell's equations and demonstrate the existence of open channels in 3D disordered media. We examine the spatial profile of such open channels, demonstrate the existence of a bimodal transmission eigenvalue distribution, and study the effects of incomplete polarization control and finite-area illumination. The simulations provide full access to all spatiotemporal properties of the complex wave transport in 3D disordered systems, filling the gap left by experimental capabilities.

Photonics-aided exceeding 200-Gb/s wireless data transmission over outdoor long-range 2 × 2 MIMO THz links at 300 GHz

Outdoor long-range terahertz (THz) communications often come at the expense of transmission rate. Moreover, the practicability of the single polarization optical/THz link, which is commonly used in the previous long-range THz demonstrations based on photonics, is extremely limited by the following two fatal defects. One is relying on active polarization control, and the other is not supporting the transparent bridging of optical polarization division multiplexed (PDM) signals for mature coherent optical communication networks. In this work, a large-capacity photonics-aided THz wireless communication system based on the outdoor long-range 2 × 2 multiple-input multiple-output (MIMO) links has been successfully demonstrated. We first build the 200-m 2 × 2 MIMO THz wireless links at the 300 GHz band. The cascaded linear and nonlinear equalizers are proposed which can significantly improve the transmission performance of 100- and 200-Gb/s PDM quadrature phase shift keying (QPSK) signals. Then an interesting 2 × 2 MIMO structure which can provide certain diversity reception gain under 200-m long-range wireless delivery using the same polarization scheme is also presented and further compared with the orthogonal polarization scheme. Since each THz receiver simultaneously receives data from both the two THz transmitters for this MIMO links, an improvement over 6 dB in receiving sensitivity and one order of magnitude in bit error ratio performance under low signal-to-noise ratio conditions can be achieved. Finally, based on the proposed cascaded equalizers and novel 2 × 2 MIMO structure, we successfully demonstrate a record-breaking 58-Gbaud (232-Gb/s) PDM-QPSK signal transmission over 200-m 2 × 2 MIMO THz wireless links. This is an important attempt for the photonics-aided THz wireless communication systems to achieve 2 × 2 MIMO transmission over a long wireless distance in the outdoors. Furthermore, attaining over 200 Gb/s at a wireless distance of 200 m also represents a key milestone for the long-range and large-capacity THz wireless communication systems.

A tunable transition metal dichalcogenide entangled photon-pair source

Entangled photon-pair sources are at the core of quantum applications like quantum key distribution, sensing, and imaging. Operation in space-limited and adverse environments such as in satellite-based and mobile communication requires robust entanglement sources with minimal size and weight requirements. Here, we meet this challenge by realizing a cubic micrometer scale entangled photon-pair source in a 3R-stacked transition metal dichalcogenide crystal. Its crystal symmetry enables the generation of polarization-entangled Bell states without additional components and provides tunability by simple control of the pump polarization. Remarkably, generation rate and state tuning are decoupled, leading to equal generation efficiency and no loss of entanglement. Combining transition metal dichalcogenides with monolithic cavities and integrated photonic circuitry or using quasi-phasematching opens the gate towards ultrasmall and scalable quantum devices.

A Polarization Control Operator for Polarized Electromagnetic Wave Designing

A Polarization Control Operator for Polarized Electromagnetic Wave Designing

A Systematic Review of Meta‐Surface Based Antennas for Thz Applications

AbstractThe growing demand for advanced wireless communication, high‐resolution imaging, and innovative medical applications in the Terahertz (THz) frequency range has driven remarkable developments in meta‐surface‐based antennas. This comprehensive review delves into the cutting‐edge advancements, novel designs, and practical applications of meta‐surfaces in the THz spectrum. The review begins by exploring the materials employed in meta‐surfaces and their crucial role in achieving efficient THz operation. It delves into the realm of polarization diversity, revealing innovative approaches to harnessing the potential of meta‐surfaces for polarization control and conversion. A key area of focus is beam‐steering technology, with a thorough investigation into beam‐steering techniques that have significant implications for enhancing wireless communication, high‐resolution imaging, and the internet of things. The paper highlights the potential of these techniques in addressing real‐world challenges and advancing THz technology. Furthermore, this review provides an in‐depth examination of the innovative antenna designs tailored for THz applications, shedding light on their characteristics and benefits. It also explores the exciting possibilities of THz technology within the medical field, including precise bio sensing and cancer cell detection.

Excitonic signatures of ferroelectric order in parallel-stacked MoS2

Interfacial ferroelectricity, prevalent in various parallel-stacked layered materials, allows switching of out-of-plane ferroelectric order by in-plane sliding of adjacent layers. Its resilience against doping potentially enables next-generation storage and logic devices. However, studies have been limited to indirect sensing or visualization of ferroelectricity. For transition metal dichalcogenides, there is little knowledge about the influence of ferroelectric order on their intrinsic valley and excitonic properties. Here, we report direct probing of ferroelectricity in few-layer 3R-MoS2 using reflectance contrast spectroscopy. Contrary to a simple electrostatic perception, layer-hybridized excitons with out-of-plane electric dipole moment remain decoupled from ferroelectric ordering, while intralayer excitons with in-plane dipole orientation are sensitive to it. Ab initio calculations identify stacking-specific interlayer hybridization leading to this asymmetric response. Exploiting this sensitivity, we demonstrate optical readout and control of multi-state polarization with hysteretic switching in a field-effect device. Time-resolved Kerr ellipticity reveals direct correspondence between spin-valley dynamics and stacking order.

The theoretical study of high-order dissipation soliton molecules evolution in a passively mode-locked fiber laser

High-order solitons represent a special form of soliton. Due to the complexity of their spatial structure and dynamic evolution, they have important applications in communication systems such as wavelength division multiplexing and secure communication. However, compared to traditional solitons, research on the spectral evolution of high-order solitons is still insufficient. In this paper, through precise control of laser parameters, the dynamic evolution process from stable dissipative single soliton to complex dissipative 8-order soliton molecules in passively mode-locked fiber lasers was successfully simulated. This demonstrates the complexity of solitons interaction and reveals the regularity of soliton molecules order with variations in four parameters: the small signal gain coefficient, nonlinear coefficient, gain bandwidth and the polarization controller angle. Through deep analysis of the order of soliton molecules, pulse shape and spectral shape of dissipative soliton molecules, we showcase the potential of fine-tuning laser parameters to achieve high-order dissipative soliton molecules. This work provides important references for the optimization design and expanded applications of lasers, further driving the development of high-performance, high-efficiency fiber laser technology.

Macrophage energy metabolism in cardiometabolic disease.

In a rapidly expanding body of literature, the major role of energy metabolism in determining the response and polarization status of macrophages has been examined, and it is currently a very active area of research. The metabolic flux through different metabolic pathways in the macrophage is interconnected and complex and could influence the polarization of macrophages. Earlier studies suggested glucose flux through cytosolic glycolysis is a prerequisite to trigger the pro-inflammatory phenotypes of macrophages while proposing that fatty acid oxidation is essential to support anti-inflammatory responses by macrophages. However, recent studies have shown that this understanding is oversimplified and that the metabolic control of macrophage polarization is highly complex and not fully defined yet. In this review, we systematically reviewed and summarized the literature regarding the role of energy metabolism in controlling macrophage activity and how that might be altered in cardiometabolic diseases, namely heart failure, obesity, and diabetes. We critically appraised the experimental studies and methodologies in the published studies. We also highlighted the challenging concepts in macrophage metabolism and identified several research questions yet to be addressed in future investigations.

Directionally Asymmetric in Orbital Angular Momentum Generation Using Single‐Layer Dielectric Janus Metasurfaces

AbstractJanus metasurfaces, offering versatile light manipulation contingent on incident direction, are explored across microwave to mid‐infrared spectra. Nonetheless, prior designs often resort to spatial multiplexing or vertical stacking, entailing complex fabrication. Metallic Janus metasurfaces, owing to material properties, suffer notable Ohmic losses in the visible spectrum. In this study, Single‐layer TiO2‐based Janus metasurfaces with arbitrary polarization control is experimentally demonstrated, exhibiting directionally asymmetric functionalities in spin and orbital angular momentum (OAM). A novel Jones matrix formulation tailored for Janus metasurfaces is presented, enabling efficient generation of two asymmetric, high‐purity OAM states of vortex beams at wavelength of 532 nm, contingent on incidence direction. This innovation facilitates compact and versatile phase manipulation, encompassing applications such as lasers and optical combiners, thereby expanding its utility across diverse domains.

Impact of polarization and gain control in the optimization of output pulse properties in ultralong ultrafast ring fibre lasers

The application of limited polarization and gain control to the recently demonstrated mode-locked ultralong ultrafast, EDFA-based and Raman-assisted pulsed ring fibre lasers is shown to reduce output pulse duration and noise, as well as to increase pulse peak power in cavities of 10 km with repetition rates as low as 38 kHz and pulse durations below 200 fs FWHM, which remain effectively depolarized at the output in the optimized case, accompanied by improved mode-locking stability. The impact of polarization state optimization prior to the doped-fibre amplification section on these devices is studied for different lengths of fibre, harmonic modes, and Raman amplification values. Peak power is nearly doubled thanks to temporal compression and spectral broadening, with a wide choice of regimes of operation dynamically available for a given cavity length, allowing the modification of laser output towards targeted pulse characteristics.

Polynomial modal method for crossed slanted gratings

Slanted gratings have emerged as a promising area of research due to their distinct properties, such as polarization control, beam steering, and enhanced interactions between light and matter. However, accurately and efficiently modeling these structures, particularly in the case of two-dimensional (2D) slanted gratings, has proven to be challenging. Traditional methods like the Fourier modal method (FMM or RCWA) and finite difference time domain (FDTD) are commonly used but involve approximations of the geometry to accommodate the slant effect. In this study, we address these challenges by employing the polynomial modal method (PMM) for 2D slanted gratings, which, to our knowledge, is a novel approach not previously explored for this type of grating. We introduce a 2D slanted coordinate system to rigorously handle the grating profile. For 2D slanted gratings, the PMM offers several advantages over the FMM, as it overcomes limitations associated with factorization rules and/or staircase approximation of the profile.

Emerging Multifunctionality in 2D Ferroelectrics: A Theoretical Review of the Interplay With Magnetics, Valleytronics, Mechanics, and Optics

Abstract2D ferroelectric materials present promising applications in information storage, sensor technology, and optoelectronics through their coupling with magnetics/valleytronics, mechanics, and optics, respectively. The integration of 2D ferroelectrics with magnetism enhances data storage density in memory devices by enabling electric‐field‐controlled magnetic states. Ferroelectric‐valley coupling holds promise for high‐speed, low‐energy electronics by leveraging the electrical control of valley polarization. Ferroelectric‐strain coupling results in various polar topologies, with potential applications in high‐density data storage technologies and sensor devices. Moreover, the coupling between ferroelectrics and optics facilitates the development of nonlinear photonics based on ferroelectric materials. This review summarizes the latest theoretical progress in the coupling mechanisms, including the Dzyaloshinskii‐Moriya‐interaction‐induced magnetoelectric coupling, symmetry‐linked ferroelectric‐valley coupling, ferroelectric‐strain‐coupling‐generated polar topologies, and second‐harmonic generation through ferroelectric‐light interactions. The current challenges and future opportunities in harnessing the coupling in 2D ferroelectric materials for multifunctional applications are provided.

Ultrafast Polarization-Resolved Phonon Dynamics in Monolayer Semiconductors.

Monolayer transition metal dichalcogenide semiconductors exhibit unique valleytronic properties interacting strongly with chiral phonons that break time-reversal symmetry. Here, we observed the ultrafast dynamics of linearly and circularly polarized E'(Γ) phonons at the Brillouin zone center in single-crystalline monolayer WS2, excited by intense, resonant, and polarization-tunable terahertz pulses and probed by time-resolved anti-Stokes Raman spectroscopy. We separated the coherent phonons producing directional sum-frequency generation from the incoherent phonon population emitting scattered photons. The longer incoherent population lifetime than what was expected from coherence lifetime indicates that inhomogeneous broadening and momentum scattering play important roles in phonon decoherence at room temperature. Meanwhile, the faster depolarization rate in circular bases than in linear bases suggests that the eigenstates are linearly polarized due to lattice anisotropy. Our results provide crucial information for improving the lifetime of chiral phonons in two-dimensional materials and potentially facilitate dynamic control of spin-orbital polarizations in quantum materials.

Reflective multi-layer metasurface based on half-wave plate structure for polarization control in the visible-near-infrared region

The precise control of the polarization of the electromagnetic field in the optical range is studied. A numerical simulation was performed, which corresponds to the optical devices operating in the 650–800 nm range and does not present any obstacles for fabrication. According to this, the three-layer system based on metasurfaces was developed, which operates as a half-wave plate consisting of a metal-dielectric-metal structure and takes very small dimensions, more than 3 times smaller than the observed wavelength. This half-wave plate is reflective and exhibits almost ideal behavior with a spectral width of about 10 nm within 735–745 nm. The losses are negligible, and the amplitude ratio of the directly reflected components in almost the entire studied spectrum exceeds 90%. With a spectrum of about 100 nm within 650–800 nm, it is 99%. Also, the system has an advantage characteristic of metasurfaces: regardless of the angle of the incident wave with the normal, it shows high efficiency, and even when the incident wave is below 45°, the polarization conversion ratio (PCR) remains greater than 80%. The system has optimal geometric dimensions, which works especially well, but even if the dimensions change (due to fabrication defects), its effectiveness does not weaken. The proposed system can become a very promising optical device and be used to control the state of electromagnetic waves in the optical range.

Scattering Elimination in 2D IR Immune from Detector Artifacts.

Highly scattering samples, such as polymer droplets or solid-state powders, are difficult to study via coherent two-dimensional infrared (2D IR) spectroscopy. Previously, researchers have employed (quasi-) phase cycling, local-oscillator chopping, and polarization control to reduce scattering, but the latter method poses a limit on polarization-dependent measurements. Here, we present a method for Scattering Elimination Immune from Detector Artifacts (SEIFDA) in pump-probe 2D IR experiments. Our method extends the negative probe delay method of removing scattering from pump-probe spectroscopy to 2D experiments. SEIFDA works well for all polarizations when combined with the optimized noise reduction scheme to remove additive and multiplicative noise. We demonstrate that our method can be employed with any polarization scheme and reliably lowers the scattering at parallel polarization to comparable levels to the conventional 8-frame phase cycling with probe chopping (8FPCPC) at perpendicular polarization. Our system can acquire artifact free spectra in parallel polarization when the signal intensity is as little as 5% of the intensity of the interference between the pump pulses scattered into the detector. It reduces the time required to characterize the scattering term by at least 50% over 8FPCPC. Through detailed analysis of detector nonlinearity, we show that the performance of 8FPCPC can be improved by incorporating nonlinear correction factors, but it is still worse than that of SEIFDA. Application of SEIFDA to study the encapsulation of Nile red in polymer droplets demonstrates that this method will be very useful for probing highly scattering systems.

Logic Computing Field-Effect Transistors Based on a Monolayer WSe2 Homojunction for the Semi-adder and Decoder.

Two-dimensional reconfigurable field-effect transistors (FETs) are promising candidates for next-generation computing hardware. However, exploring the cascade design of FETs for logic computing remains challenging. Here, by using density functional theory combined with the nonequilibrium Green's function method, we design a 5 nm split-gate FET based on a monolayer WSe2 homojunction, which can implement dynamic polarity control in different gate configurations. The series array of two FETs shows a functional family of logic gates (NOR, AND, XOR, A̅B, and AB̅), and the semi-adder designed by the logic functions AND and XOR reduces the number of transistors by 66.7%. The parallel array of two FETs demonstrates reconfigurable logic gates with NAND/OR/A̅+B/A+B̅ quadruple functions, which can realize the decoding function of 00-11 in the decoder. The cascade design of the electrically tunable FETs helps to tackle the logic device downscaling and integration dilemmas.

Deep neural network-enabled multifunctional switchable terahertz metamaterial devices

Under the support of deep neural networks (DNN), a multifunctional switchable terahertz metamaterial (THz MMs) device is designed and optimized. This device not only achieves ideal ultra-wideband (UWB) absorption in the THz frequency range but enables dual-functional polarization transformation over UWB. When vanadium dioxide (VO2) is in the metallic state, the device as a UWB absorber with an absorption rate exceeding 90% in the 2.43–10 THz range, with a relative bandwidth (RBW) of 145.2%, and its wideband absorption performance is insensitive to polarization. When VO2 is in the insulating state, the device can switch to a polarization converter, achieving conversions from linear to cross polarization and from linear to circular polarization in the ranges of 4.58–10 THz and 4.16–4.43 THz, respectively. Within the 4.58–10 THz range, the polarization conversion ratio approaches 100% with an RBW of 74.3%, the polarization rotation angle is near 90°. Within the 4.16–4.43 THz range, the RBW is 6.29% and the ellipticity ratio approaches 1, Moreover, the effects of incident angle and polarization angle on the operational characteristics are studied. This THz MMs due to its advantages of wide angle, broad bandwidth, and high efficiency, provides valuable references for the research of new multifunctional THz devices. It has great application potential in short-range wireless THz communication, ultrafast optical switches, high-temperature resistant switches, transient spectroscopy, and optical polarization control devices.

Enhanced intrinsic chiroptical response of resonant metallic metasurfaces.

The physics of resonant metasurfaces underpins many electromagnetic functionalities with enhanced performance by virtue of resonant excitations. Resonances originating from bound states in the continuum (BICs) were recently recognized in photonics for their superior optical properties, strong local field enhancement, and suppression of radiative losses. Very recently, a concept of intrinsically chiral dielectric BIC metasurfaces was proposed that combines strong narrowband resonant features with the polarization control of scattered light. Here, we design a resonant chiral metallic metasurface supporting a BIC resonance in the microwave wavelength range. In our structure, the metasurface units (meta-atoms) are characterized with rotational and mirror spatial symmetries. We numerically characterize metasurface mode properties in eigenmode calculations and scattering spectra for linearly polarized excitation under oblique incidence. Then, we investigate intrinsic chiroptical effects for transmission of normally propagating excitation beams by breaking the meta-atom in-plane mirror symmetries. We predict that the intrinsic circular dichroism in such structures may exceed 0.74.