Polarization-dependent Properties Research Articles

Emerging topological multiferroics from the 2D Rice-Mele model

We introduce a two-dimensional dimerized lattice model that reveals a remarkable feature: the emergence of a complex, non-trivial topological multiferroic phase marked by zero Berry curvature and a significant Berry connection that influences the model’s bulk topology. This model extends the one-dimensional Rice-Mele Hamiltonian model to explore polarization-dependent topological properties in a 2D Su-Schrieffer-Heeger lattice, providing a detailed framework for studying the impact of symmetry-breaking and spatially varying potentials on electronic and spin properties. The findings are particularly relevant for spintronics, offering a foundation for topologically robust and electrically controlled spin-conducting edge states, with implications for developing advanced spin-dependent transport devices.

Dual-band high quality-factor perfect absorber based on uniaxial/biaxial anisotropic van der Waals polar crystals

Phonon polaritons (PhPs) in two-dimensional van der Waals crystals, such as hexagonal boron nitride (hBN) and α-phase molybdenum trioxide (α-MoO3), exhibit remarkable spatial confinement and extremely low optical losses, offering possibilities for the development of novel micro and nanophotonic devices at mid-infrared wavelengths. Here, we demonstrate the potential of the proposed Tamm structure to achieve dual-band high quality-factor perfect absorption within the mid-infrared range. This structure utilizes upper and lower spacer layers to isolate the anisotropic materials hBN and α-MoO3 from one-dimensional photonic crystals, where the Tamm phonon polaritons (TPhPs) are respectively excited at the interfaces, facilitating strong coupling with incident light and leading to significant dual-band perfect absorption phenomena. The results demonstrate that due to polariton resonances, the absorption peaks exhibit extremely narrow absorption bandwidths, with the maximum quality-factor reaching up to 297. In addition, tunable resonant wavelengths and polarization-dependent absorption properties are also demonstrated in the proposed Tamm structure. This study provides an alternative and straightforward approach for constructing dynamic and multifunctional optical devices such as optical modulators, tunable multi-band filters and biosensors.

Mechanically induced long period gratings in different silica multi-layered optical fibers

This work presents a thorough comparative investigation of mechanically induced long period gratings (MILPGs) realized in different unconventional multi-layered silica optical fibers: two double cladding fibers (DCF), with progressively three layered (PTL) and W-type structures, and a solid core photonic crystal fiber (PCF). A periodic interdigitated grooved structure, based on the stereo-lithography 3D printing technique, is developed for the grating formation in these fibers with simplicity and cost-effectiveness. Multiple grating periods are developed in the range 480–660 μm, resulting in attenuation bands with depth within 15–25 dB and wide range of tunability over the wavelength range of 1100–1700 nm. The results demonstrate effective management of transmission spectra evolution as a function of the applied weight, with minimal alteration in wavelength position when testing the fiber with or without its coating. Polarization dependent properties of these gratings are also investigated demonstrating a negligible impact. This is the first time that such a broad investigation is conducted about MILPGs in the fibers mentioned earlier with broad scouting in fabrication parameters, opening to the application of such devices for sensing and communication purposes.

Lithography-free directional control of thermal emission

Abstract Blackbody radiation is incoherent and omnidirectional, whereas various novel applications in renewable energy require a degree of directional control of a thermally emitted beam. So far, such directional control has required nano-structuring the surface of a thermally emitting material, typically by forming diffraction gratings. This, however, necessitates lithography and usually results in polarization-dependent properties. Here, we derive analytical conditions for highly directional thermal emission using a planar 3-layer structure analogous to a Salisbury screen. We present design rules for maximizing the directionality of such structures. Notably, these design rules pertain to both linear polarizations, thus generalizing the principles of a grating for unpolarized light. We show that the key requirement to achieve such performance is ultra-high quality factor resonances in materials supporting phonon polaritonic modes, as those found in low-dimensional materials. We propose a realistic device based on hexagonal Boron Nitride and predict performances comparable to lithography-based nano-structures.

Slot-Waveguide Based All-Optical RF Spectrum Analyzer

All-optical radio-frequency spectrum analyzers (AORFSAs) with ultrabroad bandwidth break the electronic bottleneck and provide an efficient frequency analysis means for ultrafast optical signals in communications, signal generation and processing systems. Here, we propose and experimentally demonstrate an AORFSA built on the cross-phase modulation effect in a 50 cm long CMOS-compatible photonic slot-waveguide. The waveguide has a 100 nm thick thin-film core of fused silica that is sandwiched by two 750 nm thick cladding layers of high-index doped silica, which shows optimized dispersion and comparable nonlinear characteristics. The measured 3 dB bandwidth of the proposed slot-waveguide-based AORFSA has a three-fold increase over the conventional channel waveguide having the same dimension and length. The sensitivity and wavelength- and polarization-dependence properties are investigated, confirming the proposed waveguide as a versatile platform for frequency analysis of ultrafast optical signals, such as Kerr microcombs with hundreds of GHz or even THz mode spacing.

Strong polarization-dependent photonic bandgap and giant photonic spin Hall effect in a one-dimensional photonic crystal entirely composed of all-dielectric metamaterials

In conventional one-dimensional (1-D) photonic crystals (PhCs) consisting of isotropic dielectrics, photonic bandgaps (PBGs) exhibit weak polarization-dependent property since the propagating phase of the isotropic dielectric film is polarization-independent. The weak polarization-dependent property of PBGs intensively impedes the potential application of 1-D PhCs in the photonic spin Hall effect (PSHE). Herein, we investigate the polarization-dependent property of PBGs in a class of 1-D PhCs entirely consisting of all-dielectric elliptical metamaterials (EMMs) called all-EMM 1-D PhCs. Driven by the combination of 1-D PhCs and all-dielectric EMMs, strong polarization-dependent PBGs can be realized. Then, we exploit the strong polarization-dependent PBG to achieve giant PSHE. The enhanced transverse shift of the PSHE reaches the order of 102 μm. Our work not only establishes a bridge between PhCs and all-dielectric metamaterials, but also paves a new route to manipulating polarization of light.

Graphene/Cholesteric Liquid-Crystal-Based Electro-Driven Thermochromic Light Modulators toward Wide-Gamut Dynamic Light Color-Tuning-Related Applications.

Light filters are ubiquitous in projection and display techniques, illumination engineering, image sensing, photography, etc., while those enabling wide-gamut dynamic light color tuning are still lacking. Herein, by combining the electro-heating capability of graphene and unique optical properties (thermochromism and circular dichroism) of small-molecule-weight cholesteric liquid crystal (ChLC), a brand-new thermochromic light modulator is constructed as actively tunable color filter. Transparent graphene/glass hybrid with reasonably high conductivity serves both as a high-performance heater for actuating the thermochromism of temperature-responsive ChLC and as neutral light attenuator for brightness control. Thanks to the temperature- and polarization-dependent spectral properties of the ChLC, widely tunable hue and saturation properties of transmission light color are achieved, respectively. Several intriguing applications, e.g., color-variable smart windows for backlight color tuning and color-variable filters for photography, are also demonstrated. This work hereby provides new paradigms for promoting the applications of graphene/ChLC-based light modulators in next-generation light-management-related scenarios.

Giant photonic spin Hall effect empowered by polarization-dependent quasibound states in the continuum in compound grating waveguide structures

The photonic spin Hall effect (PSHE) plays an important role in both fundamental science and precision metrology. In this paper, we theoretically propose a polarization-dependent bound state in the continuum (BIC) in a compound grating waveguide structure based on the selectable guided resonance at near-infrared wavelengths. Empowered by the unique resonant property and polarization-dependent property of the quasi-BIC, the transverse shift of the PSHE can be intensively enhanced to the order of hundreds of micrometers. Besides, the enhancement of the transverse shift of the PSHE is robust against the geometric parameters. Our work not only provides an all-dielectric platform to achieve giant PSHE, but also offers a viable approach to design high-performance PSHE-based optical devices.

Plasmon-enhanced upconversion luminescence on horizontally aligned gold nanorod arrays with self-contained spacer

The growing interest in converting infrared light to visible light in many photovoltaic fields requires the development of upconversion systems with high luminescence quantum yields and stability without blinking. However, the weak and narrow absorption of rare earth ions has greatly restricted the luminescent efficiency of rare earth dopants and hampered their translation from experimental research to real world applications. In this work, horizontally aligned gold nanorod arrays with self-contained spacer and obvious polarization dependent plasmonic properties are prepared on the substrate of silicon wafers by a self-assembly method of droplet evaporation, and polarization-dependent enhancement on the upconversion luminescence of rare earth ions doped nanoparticles (NaYF4: Yb3+, Er3+) are investigated. The results show that the luminescence intensity of the nanoparticles is greatly enhanced by a factor of about 140, when the horizontally aligned gold nanorod arrays are available as a substrate. The effect of self-contained spacer of the arrays to prevent quenching of the luminescence is investigated with the introduction of an Al2O3 layer as an isolate and the adjustment of its thickness. It is found that the self-contained spacer can effectively block the non-radiative energy transfer without the need of additional spacer. In addition, the horizontally aligned gold nanorod arrays also exhibit excellent optical polarization anisotropy. As the polarization angle of the incident light gradually increases, the intensity of the fluorescent radiation decreases, which is interpreted and analyzed by simulating the near field distribution. This strategy not only provides a powerful solution to build high-efficiency surface enhanced fluorescence systems, but also suggests a new pathway to realize the polarization-selective excitation of upconversion luminescence.

Ultra-compact bifunctional transparent meta-device based on bi-layer anisotropic Huygens’ metasurface

Bifunctional transparent meta-devices play an essential role in electromagnetic (EM) integration because of their advantages in extensive applications in modern devices. However, most available devices are achieved by multi-layer dielectric cascaded structures due to the requirement of 360° transmission phase shift, which suffer from the issues of high loss, complex mode control, complicated fabrication and device-integration inconvenience. Herein, a bi-layer anisotropic Huygens’ metasurface is proposed to design ultra-compact bifunctional transparent meta-devices based on the polarization dependent property via inducing the orthogonal electric and magnetic currents simultaneously to excite the Huygens’ resonance. As proof of the concept, a bifunctional transparent meta-device is designed, fabricated and experimentally demonstrated, which behaves as a beam deflector and a focusing lens under excitation of x-polarized and y-polarized incident waves, respectively. Numerical results coincide well with the experiments, indicating that the measured total efficiency of the beam deflector is about 64% at 10 GHz and the measured relative efficiency of the focusing lens achieves about 80%. Our findings provide a novel low-cost, easy-to-fabricate and convenient-to-setup solution for bifunctional transparent meta-devices and could stimulate their promising applications in many EM integration systems.

Spinning thermal radiation from twisted two different anisotropic materials.

Thermal radiation has applications in numerous fields, such as radiation cooling, thermal imaging, and thermal camouflage. Micro/nanostructures such as chiral metamaterials with polarization-dependent or symmetry-breaking properties can selectively emit circularly (spin) polarized polarization waves. In this paper, we propose and demonstrate the spinning thermal radiation from two twisted different anisotropic materials. Taking industrial polymer and biaxial hyperbolic material α-MoO3 as an example, it is found that broadband spinning thermal radiation can be obtained from 13 µm to 18 µm. The spin thermal radiation of the proposed twisted structure originates from the combined effect of polarization conversion of circularly polarized wave and selective absorption of linearly polarized wave by the top and bottom layers of anisotropic materials, respectively. Besides, the narrowband spinning thermal radiation with 0.9 circular dichroism is achieved at wavelength of 12.39 µm and 18.93 µm for finite thickness α-MoO3 due to the epsilon-near-zero mode, and the magnetic field distribution can confirm the phenomenon. This work achieves broadband and narrowband spin thermal radiation and significantly enhances circular dichroism, which may have applications in biological sensing and thermal detection.

Multi-path remote-excited surface plasmon resonance of a hollow gold nanosheet studied using FDTD simulations

Multi-path remote-excited surface-enhanced Raman scattering (SERS) could be achieved in a two-dimensional hollow gold nanosheet (HGNS) structure. This structure typically contains one hollow and regular cavity located concentrically in the middle of a gold nanosheet (GNS), which forms such as Triangle-Triangle (T-T) or Hexagon-Hexagon (HH) HGNS. As for T-T HGNSs, if we focused the exciting incident laser on one vertex of the outer-solid-triangle (OST) or inner-hollow-triangle (IHT), the localized surface plasmon resonance (LSPR) could be achieved on other remote vertexes. Because of this hollow cavity (e.g. IHT in T-T HGNSs), the maximum quad-path remote-excited SERS system could be developed. The optical property of equilateral triangular and solid GNS (SGNS) is comparatively simple and symmetric. However, after a hollow triangle cavity is formed within GNS, it can be used to modulate LSPR and bring in a new coupling effect between OST and IHT. FDTD simulations have shown that a red-shift of LSPR peak with the increase of IHT size were observed. Compared with single-path-excitation, the remote signal of LSPR scattering at wavelength around 0.76 μm can be enhanced, under the optimum coupling polarization, by over 228 %, 597 % and 1155 % for dual-, triple- and quad-path-excitation respectively. At given LSPR peak (e.g. around 1.061 μm), this enhancement can be doubled once again at least. Furthermore, a remarkable polarization-dependent anisotropic property in T-T HGNS was observed owing to strong OST-IHT couplings, which exhibits great potential application in remote SERS, remote sensing and optical waveguide switch.

Polarization-dependent photoluminescence properties of fab-compatible nanowire-based nanophotonic structures

Semiconductor nanowires show great potential for controlling light–matter interactions. Moreover, their polarization-dependent optical properties, primarily enabled by their dielectric mismatch, are a significant requisite for a plethora of emerging applications spanning from polarized photodetection to quantum photonics and quantum communication. Herein, we study the polarization dependence of photoluminescence (PL) properties from fab-compatible nanophotonic structures, comprising arrays of ultrathin (20 nm) silicon carbide nanowires (NWs) doped with oxygen and erbium ions. Polarization-resolved PL studies demonstrate a significant excitation polarization anisotropy (∼0.7) of the visible NW PL for light polarized parallel and perpendicular to the NWs' long axis. This anisotropic behavior agrees with our simulations and with the classical dielectric contrast model and is consistent across the investigated periodicity range of the NW arrays. Furthermore, the effect of this anisotropy on the NW carrier dynamics is explored through power-dependence and transient PL measurements. We have observed a faster carrier lifetime for light polarized parallel to the NWs than the perpendicular polarization. Finally, we demonstrate a translation of this polarization dependence to the technologically significant erbium-induced 1540 nm emission from the erbium centers in the NW arrays. The ability to engineer emission polarization and placement of these centers in the NW array offers a promising platform for emission enhancement of telecom emitters through effective coupling to optical nanocavities for applications in chip-scale photonics and quantum photonics.

Carbon nanotube logic gates: An interplay of spin and light

Carbon nanotubes (CNTs) are known to be the future of modern electronic devices due to their unique structure and extraordinary properties. In this paper, we modeled a first of its kind combinational carbon nanotube device consisting of a lanthanum strontium manganite molecule fused near the left CNT electrode and four-atom boron–nitrogen dopant atoms substituted near the right CNT electrode. Spin-resolved transport properties are studied using density functional theory. It is observed from the results that spin-resolved transport properties highly depend on the type of magnetic field applied and light conditions. The device shows efficient switching pattern and high spin filtration. The observations are made by calculating I–V characteristics, spin dependent transmission spectra, and molecular projected self-consistent Hamiltonian orbitals. Using light and spin polarization dependent properties, we have designed and realized the logic operations of and, or, and not gates. The study is useful to design a number of futuristic spin and light controlled electronic devices such as transistors, amplifiers, and oscillators.

Beam Manipulations With Compact Planar Dielectric Pancharatnam–Berry Phase Devices

The growth spurt of novel planar optical devices in recent years has been greatly facilitated by the rapid development of artificial material designing and nanoprocessing technology. Traditional optical phase gradient devices cannot be scaled down to sub-wavelength size due to the confinement of the optical path difference required for versatile phase manipulation, so new strategies are urgently needed to design compact planar devices. Here, we develop a series of novel compact planar devices that break the thickness limitation by taking advantage of the superpositionable, polarization-dependent properties of the Pancharatnam–Berry phase. Among them, representative compact devices are fabricated using well-designed dielectric glass plates. Our compact devices therefore offer a novel and simple scheme to circumvent the accumulation of transmission loss in a cascade system of phase gradient devices.

Suppressed Blinking and Polarization-Dependent Emission Enhancement of Single ZnCdSe/ZnS Dot Coupled with Au Nanorods.

Fluorescent quantum dots (QDs) have attracted extensive attention because of their promising applications in many fields such as quantum optics, optoelectronics, solid-state lighting, and bioimaging. However, photo-blinking, low emission efficiency, and instability are the drawbacks of fluorescent QD-based devices, affecting their optical properties and practical applications. Here, we report suppressed blinking, enhanced radiative rate, and polarization-dependent emission properties of single ZnCdSe/ZnS QDs assembled on the surface of Au nanorods (NRs). We found that the local surface plasmon (LSP) of Au NRs significantly regulates the excitation and emission properties of the composite ZnCdSe/ZnS QD-Au NRs (QD-Au NRs). The average number of photons emitted per unit time from single QD-Au NRs has been significantly enhanced compared with that of single ZnCdSe/ZnS QDs on the coverslip, accompanied by a drastically shortened lifetime and suppressed blinking. According to the experimental and simulation analysis, the photogenerated LSP field of Au NRs remarkably increases the excitation transition and the radiative rates of QD-Au NRs. Although the emission efficiency is slightly increased, the synergetic enhancement of excitation and radiative rates sufficiently competes with the nonradiative process to compensate for the low emission efficiency of QDs and ultimately suppress the photo-blinking of QD-Au NRs. Moreover, the polarization-dependent emission enhancement has also been observed and theoretically analyzed, demonstrating good consistency and confirming the contribution of excitation enhancement. Our findings present a practical strategy to improve the optical properties and stability of single QD-Au NR composite and provide essential information for a deep understanding of the interaction between emitters and the LSP field of metal nanoparticles.

Bifunctional spoof surface plasmon polariton meta-coupler using anisotropic transmissive metasurface

Abstract Tailoring the wavefronts of spoof surface plasmon polaritons (SSPPs) at will, especially with multifunctional integration, is of great importance in near-field photonics. However, conventional SSPP devices suffer from the issues of bulk configurations, limited functionalities, and single operating modes, which are unfavorable for electromagnetic (EM) integration. Here, a novel scheme is proposed to design bifunctional SSPP meta-devices based on the polarization dependent property via satisfying the comprehensive phase distributions and multi-mode momentum matching in a transmission geometry. As proof of the concept, we experimentally demonstrate a bifunctional SSPP meta-device in the microwave regime that can convert incident x- and y-polarized waves to transverse magnetic (TM)-mode SSPP Bessel beams and transverse electric (TE)-mode SSPP focusing beams, respectively. Our findings open a door to achieve near-field manipulation of SSPPs with multi-function and multi-mode integration, which can stimulate the applications of SSPP functional devices, such as near-field sensing, imaging, and on-chip photonics.

Design of InAs nanosheet arrays with ultrawide polarization-independent high absorption for infrared photodetection

InAs nanowires have been considered as good candidates for infrared photodetection. However, one-dimensional geometry of a nanowire makes it unsuitable for broadband light absorption. In this work, we propose and design InAs nanosheet arrays to achieve polarization-independent, angle-insensitive, and ultrawide infrared absorption. Simulations demonstrate that two-dimensional InAs nanosheets can support multiple resonance modes, thus leading to a strong and broadband absorption from visible light to mid-wave infrared. Moreover, we can tune polarization-dependent property in InAs nanosheets to be polarization-insensitive by forming a nanosheet based clover-like and snowflake-like nanostructures. We further optimized the design of InAs nanosheet arrays based on such structures and achieved high absorption (up to 99.6%) covering a broad wavelength range from 500 to 3200 nm. These absorption properties are much superior to their nanowire and planar film counterparts, making it attractive for infrared photodetection applications. The architecture of such nanostructures can provide a promising route for the development of high-performance room-temperature broadband infrared photodetectors.

Controllable polarization dependence in quantum dots and silver nanowire coupling system

Owe to the ability of supporting propagating surface plasmons, silver nanowire can be decent candidate as optical nanoantenna to modulate the polarization property of nano-emitters. Here, we created a quantum dots and silver nanowire coupling system to implement the controllable polarization dependence of this antenna effect. Several basic modes are mainly explored with both positive and negative excitation and observation directions. For the contrast excitation directions, both the center and the end fluorescence spots have reverse polarization dependence characterizations. While the controllable polarization dependence only appears at the center spot for the different observation angles. Based on these modes, diverse polarization dependence properties can be extended flexibly. The reasons for the phenomena are explained using the theoretical simulation. The numerical calculation shows the silver nanowire can act both optical receiving antenna and transmitting antenna in this process. Achieving on the controllable polarization dependence, our results are useful in the investigation about the coupling of nano-emitters and optical antenna.

Efficient few-cycle Yb-doped laser oscillator with Watt-level average power.

So far, the operation of ultrafast bulk laser oscillators based on Yb-doped gain materials and directly emitting few-cycle pulses have been restricted to low optical-to-optical efficiencies and average output powers of only a few milliwatt. This performance limitation can be attributed to the commonly-applied standard collinear pumping scheme in which the optical pump is transmitted through a dichroic mirror whose spectral transmission and dispersion properties severely perturb the oscillating pulse when its optical spectrum extends towards the pump wavelength. In this study, we report on a novel pumping scheme relying on cross polarization that overcomes this challenge. In our concept, the pump transmitting mirror is highly transmissive for the pump light in p-polarization, while it is highly reflective for the laser light in s-polarization over a broad wavelength range, even covering the pump wavelength and beyond. In contrast to a standard thin-film polarizer featuring similar polarization dependent properties, it provides a low and flat dispersion profile over a broad spectral range for the s-polarization. Implementing this pumping scheme in a soft-aperture Kerr-lens mode-locked bulk laser oscillator based on the gain material Yb:CALGO, we achieve clean 22-fs soliton pulses at 729 mW of average output power and an optical-to-optical efficiency of 25%. In a second configuration optimized for the highest average output power, we demonstrate a high optical-to-optical efficiency of 36.6%, which was obtained for 31-fs pulses at 1.63 W of average output power. In a third configuration we experimentally confirm the limiting effect of a dichroic mirror commonly used in the standard collinear pumping scheme. All the results presented here and obtained in the first and second configuration generate pulses with a center wavelength ranging from 1030 nm to 1056 nm, well within the spectral region of high gain cross sections of Yb:CALGO. While this initial demonstration was realized using a commercial diffraction-limited fiber laser as pump source, the pump geometry appears also well suited for pumping with laser diodes coupled into multimode fibers. This novel approach opens up new opportunities for compact and cost-efficient high-power few-cycle bulk laser oscillators based on Yb-doped gain materials and can be applied to any gain material with small quantum defect.