Showing papers on "Circular polarization published in 2019"

Photonic Cyclone: spatiotemporal optical vortex with controllable transverse orbital angular momentum.

Abstract: Today, it is well known that light possesses a linear momentum which is along the propagation direction. Besides, scientists also discovered that light can possess an angular momentum (AM), a spin angular momentum (SAM) associated with circular polarization and an orbital angular momentum (OAM) owing to the azimuthally dependent phase. Even though such angular momenta are longitudinal in general, a SAM transverse to the propagation has opened up a variety of key applications [1]. In contrast, investigations of the transverse OAM are quite rare due to its complex nature. Here we demonstrate a simple method to generate a three dimensional (3D) optical wave packet with a controllable purely transverse OAM. Such a wave packet is a spatiotemporal (ST) vortex, which resembles an advancing cyclone, with optical energy flowing in the spatial and temporal dimension. Contrary to the transverse SAM, the magnitude of the transverse OAM carried by the photonic cyclone is scalable to a larger value by simple adjustments. Since the ST vortex carries a controllable OAM in the unique transverse dimension, it has a strong potential for novel applications that may not be possible otherwise. The scheme reported here can be readily adapted for the other spectra regime and different wave fields, opening tremendous opportunities for the study and applications of ST vortex in much broader scopes.

Enantiospecific Optical Enhancement of Chiral Sensing and Separation with Dielectric Metasurfaces

Abstract: Circularly polarized light (CPL) exhibits an enantioselective interaction with chiral molecules, providing a pathway toward all-optical chiral resolution. High index dielectric nanoparticles have been shown to enhance this relationship, but with a spatially varying sign (or enantiospecificity) that yields a near zero spatially averaged enhancement. Using full field electromagnetic simulations, we design metasurfaces consisting of high index dielectric disks that provide large-volume, uniform-sign enhancements in both the optical density of chirality, C (the figure of merit for sensing and spectroscopy), and Kuhn’s dissymmetry factor, g (the figure of merit for separation). By varying disk radius, we achieve local enhancements in C and g up to 138-fold and 15-fold, respectively, as well as volumetric enhancements of 30-fold and 4.2-fold. The uniform-sign enhancements in C occur near the first Kerker condition, where overlapping electric and magnetic modes maximize field strength and preserve the π/2 phase ...

Nature-inspired chiral metasurfaces for circular polarization detection and full-Stokes polarimetric measurements.

Abstract: The manipulation and characterization of light polarization states are essential for many applications in quantum communication and computing, spectroscopy, bioinspired navigation, and imaging. Chiral metamaterials and metasurfaces facilitate ultracompact devices for circularly polarized light generation, manipulation, and detection. Herein, we report bioinspired chiral metasurfaces with both strong chiral optical effects and low insertion loss. We experimentally demonstrated submicron-thick circularly polarized light filters with peak extinction ratios up to 35 and maximum transmission efficiencies close to 80% at near-infrared wavelengths (the best operational wavelengths can be engineered in the range of 1.3–1.6 µm). We also monolithically integrated the microscale circular polarization filters with linear polarization filters to perform full-Stokes polarimetric measurements of light with arbitrary polarization states. With the advantages of easy on-chip integration, ultracompact footprints, scalability, and broad wavelength coverage, our designs hold great promise for facilitating chip-integrated polarimeters and polarimetric imaging systems for quantum-based optical computing and information processing, circular dichroism spectroscopy, biomedical diagnosis, and remote sensing applications. Inspired by the polarization-sensitive vision of the compound eyes in a marine crustacean called the Mantis Shrimp, researchers from Arizona State University, US have designed a chiral metasurface for manipulating the polarization of light. The metasurface design consists of a thin nanostructured silicon layer, a dielectric spacer layer and a gold nanowire polarizer, and has a total thickness of less than 1 micrometer. This thin planar surface offers low optical loss with a transmission as high as 80% in the near-infrared wavelength range, and acts as a circular polarization filter with an extinction ratio as high as 35. The circular polarization filters, in combination with linear polarization filters, can enable chip-scale polarimeters for sensing the polarization state of light. This on-chip integrated approach could prove useful in ultra-compact devices for advanced imaging and sensing applications.

Interference-assisted kaleidoscopic meta-plexer for arbitrary spin-wavefront manipulation

Abstract: Achieving simultaneous polarization and wavefront control, especially circular polarization with the auxiliary degree of freedom of light and spin angular momentum, is of fundamental importance in many optical applications. Interferences are typically undesirable in highly integrated photonic circuits and metasurfaces. Here, we propose an interference-assisted metasurface-multiplexer (meta-plexer) that counterintuitively exploits constructive and destructive interferences between hybrid meta-atoms and realizes independent spin-selective wavefront manipulation. Such kaleidoscopic meta-plexers are experimentally demonstrated via two types of single-layer spin-wavefront multiplexers that are composed of spatially rotated anisotropic meta-atoms. One type generates a spin-selective Bessel-beam wavefront for spin-down light and a low scattering cross-section for stealth for spin-up light. The other type demonstrates versatile control of the vortex wavefront, which is also characterized by the orbital angular momentum of light, with frequency-switchable numbers of beams under linearly polarized wave excitation. Our findings offer a distinct interference-assisted concept for realizing advanced multifunctional photonics with arbitrary and independent spin-wavefront features. A variety of applications can be readily anticipated in optical diodes, isolators, and spin-Hall meta-devices without cascading bulky optical elements.

Single-Layer Dual-Band Linear-to-Circular Polarization Converter With Wide Axial Ratio Bandwidth and Different Polarization Modes

Abstract: A dual-band linear-to-circular polarization converter (LCPC) based on a single-layer dielectric substrate is proposed. The element of the converter consists of two identical metallic layers with a combination of a connected Jerusalem cross (JC) and an “I”-type dipole for each layer. The proposed converter is designed by using an equivalent circuit model (ECM). Left-handed circularly polarized (LHCP) and right-handed circularly polarized (RHCP) beams can be, respectively, generated at ${K}$ -band and Ka -band excited by a linearly polarized (LP) wave tilted 45° relative to the ${x}$ - and ${y}$ -directions of the converter. In addition, the converter covers two operation bands for ${K}$ -/ Ka -band satellite communications with high conversion efficiency and low polarization extinction ratio (PER). After full-wave optimization, the proposed converter is fabricated and measured. The measured results show a good agreement with the simulated ones. Even though there exists a tradeoff between the angular stability and the bandwidth of the dual-band LCPCs, the measured axial ratio (AR) remains stable in the lower operation band and a slight fluctuation in the higher band with the incident angle of 20°.

Conversion between polarization states based on a metasurface

Abstract: Transmission of an anisotropic metasurface is analyzed in a polar base relying on the Jones calculus, and polarization conversion from the spatial uniform polarization to the spatial nonuniform polarization is explored. Simple and compact polarization converters based on rectangular holes or cross holes etched in silver film are designed, and polarization conversions from the linear and circular polarization to the radial and azimuthal polarization are realized. Numerical simulations of three designed polarization converters consisting of rectangular holes equivalent to polarizers and quarter- and half-wave plates, exhibit the perfect polarization conversion. The experiment results consistent with the simulations verify theoretic predictions. This study is helpful for designing metasurface polarization converters and expanding the application of a metasurface in polarization manipulations.

Linear and circular-polarization conversion in X-band using anisotropic metasurface.

Abstract: An ultrathin single-layer metasurface manifesting both linear cross-polarization conversion (CPC) and linear-to-circular polarization (LP-to-CP) conversion in X-band is presented in this research. The designed metasurface acts as a multifunctional metasurface achieving CPC over a fractional bandwidth of 31.6% (8–11 GHz) with more than 95% efficiency while linear-to-circular polarization conversion is realized over two frequency bands from 7.5–7.7 GHz and 11.5–11.9 GHz. Moreover, the overall optimized structure of the unit cell results in a stable polarization transformation against changes in the incidence angle up to 45° both for transverse-electric (TE) and transverse-magnetic (TM) polarizations. The proposed metasurface with simple structure, compact size, angular stability and multifunctional capability qualifies for many applications in communication and polarization manipulating devices.

Direct polarization measurement using a multiplexed Pancharatnam–Berry metahologram

Abstract: Polarization, which represents the vector nature of electromagnetic waves, plays a fundamental role in optics. Fast, simple, and broadband polarization state characterization is required by applications such as polarization communication, polarimetry, and remote sensing. However, conventional polarization detection methods face great difficulty in determining the phase difference between orthogonal polarization states and often require a series of measurements. Here, we demonstrate how polarization-dependent holography enables direct polarization detection in a single measurement. Using a multiplexed Pancharatnam–Berry phase metasurface, we generate orthogonally polarized holograms that partially overlap with a spatially varying phase difference. Both amplitude and phase difference can be read from the holographic image in the circular polarization basis, facilitating the extraction of all Stokes parameters for polarized light. The metahologram detects polarization reliably at several near-infrared to visible wavelengths, and simulations predict broadband operation in the 580–940 nm spectral range. This method enables fast and compact polarization analyzing devices, e.g., for spectroscopy, sensing, and communications.

Highly efficient generation of Bessel beams with polarization insensitive metasurfaces.

Abstract: We present a generic approach for the generation of pseudo non-diffracting Bessel beams using polarization insensitive metasurfaces with high efficiency. Cascaded unit cells, which are fully symmetric, are designed for the complete 2π phase control in the transmission mode. Based on the topological arrangements of such unit cells, two metasurfaces for the generation of zero-order (i.e., single phase profile) and first-order (i.e., merger of two distinct phase profiles) Bessel beams are designed and characterized. Both numerical simulations and experimental measurements are in agreement with each other, confirming the electromagnetic characteristics of the reported Bessel beams. Owing to the isotropy of the unit cells and the rotational symmetry of the arrangements, the proposed metasurfaces are polarization insensitive, providing a promising avenue for achieving such wave manipulations with any linear or circular polarization.

Spin-Selective Transmission in Chiral Folded Metasurfaces

Abstract: Controlling the spin angular momentum of light (or circular polarization state) plays a crucial role in the modern photonic applications such as optical communication, circular dichroism spectroscopy, and quantum information processing. However, the conventional approaches to manipulate the spin of light require naturally occurring chiral or birefringent materials of bulky sizes due to the weak light–matter interactions. Here we experimentally demonstrate an approach to implement spin-selective transmission in the infrared region based on chiral folded metasurfaces that are capable of transmitting one spin state of light while largely prohibiting the other. Due to the intrinsic chirality of the folded metasurface, a remarkable circular dichroism as large as 0.7 with the maximum transmittance exceeding 92% is experimentally demonstrated. The giant circular dichroism is interpreted within the framework of charge-current multipole expansion. Moreover, the intrinsic chirality can be readily controlled by mani...

Chiral excitonic organic photodiodes for direct detection of circular polarized light

Abstract: A facile route to soft matter self-powered bulk heterojunction photodiode detectors sensitive to the circular polarization state of light is shown based on the intrinsic excitonic circular dichroism of the photoactive layer blend. As light detecting materials, enantiopure semiconducting small molecular squaraine derivates of opposite handedness are employed. Via Mueller matrix ellipsometry, the circular dichroism is proven to be of H-type excitonic nature and not originating from mesoscopic structural ordering. Within the green spectral range, the photodiodes convert circular polarized light into a handedness-dependent photocurrent with a maximum dissymmetry factor of ±0.1 corresponding to 5% overall efficiency for the polarization discrimination under short circuit conditions. On the basis of transfer matrix optical simulations, it is rationalized that the optical dissymmetry fully translates into a photocurrent dissymmetry for ease of device design. Thereby, the photodiode's ability to efficiently distinguish between left and right circularly polarized light without the use of external optical elements and voltage bias is demonstrated. This allows a straightforward and sustainable future design of flexible, lightweight, and compact integrated platforms for chiroptical imaging and sensing.

Broadband Linear-to-Circular Polarization Conversion Enabled by Birefringent Off-Resonance Reflective Metasurfaces

Abstract: Due to the scarcity of circular polarization light sources, linear-to-circular polarization conversion is required to generate circularly polarized light for a variety of applications. Despite significant past efforts, broadband linear-to-circular polarization conversion remains elusive particularly in the terahertz and midinfrared frequency ranges. Here we propose a novel mechanism based on coupled mode theory, and experimentally demonstrate at terahertz frequencies that highly efficient (power conversion efficiency approaching unity) and ultrabroadband (fractional bandwidth up to 80%) linear-to-circular polarization conversion can be accomplished by the judicious design of birefringent metasurfaces. The underlying mechanism operates in the frequency range between well separated resonances, and relies upon the phase response of these resonances away from the resonant frequencies, as well as the balance of the resonant and nonresonant channels. This mechanism is applicable for any operating frequencies from microwave to visible. The present Letter potentially opens a wide range of opportunities in wireless communications, spectroscopy, and emergent quantum materials research where circularly polarized light is desired.

Circular Dichroism Measurement of Single Metal Nanoparticles Using Photothermal Imaging.

Abstract: Circular dichroism (CD) spectroscopy is a powerful optical technique for the study of chiral materials and molecules. It gives access to an enantioselective signal based on the differential absorption of right and left circularly polarized light, usually obtained through polarization analysis of the light transmitted through a sample of interest. CD is routinely used to determine the secondary structure of proteins and their conformational state. However, CD signals are weak, limiting the use of this powerful technique to ensembles of many molecules. Here, we experimentally realize the concept of photothermal circular dichroism, a technique that combines the enantioselective signal from circular dichroism with the high sensitivity of photothermal microscopy, achieving a superior signal-to-noise ratio to detect chiral nano-objects. As a proof of principle, we studied the chiral response of single plasmonic nanostructures with CD in the visible range, demonstrating a signal-to-noise ratio better than 40 with only 30 ms integration time for these nanostructures. The high signal-to-noise ratio allows us to quantify the CD signal for individual nanoparticles. We show that we can distinguish relative absorption differences for right circularly and left circularly polarized light as small as gmin = 4 × 10-3 for a 30 ms integration time with our current experimental settings. The enhanced sensitivity of our technique extends CD studies to individual nano-objects and opens CD spectroscopy to numbers of molecules much lower than those in conventional experiments.

Ferroicity-driven nonlinear photocurrent switching in time-reversal invariant ferroic materials

Abstract: Nonlinear optical responses to external electromagnetic field, characterized by second- and higher-order susceptibilities, play crucial roles in nonlinear optics and optoelectronics. Here, we demonstrate the possibility to achieve ferroicity-driven nonlinear photocurrent switching in time-reversal invariant multiferroics. It is enabled by the second-order current response to electromagnetic field whose direction can be controlled by both internal ferroic orders and external light polarization. Second-order direct photocurrent consists of shift current and circular photocurrent under linearly and circularly polarized light irradiation, respectively. We elucidate the microscopic mechanism in a representative class of two-dimensional multiferroic materials using group theoretical analyses and first-principles theory. The complex interplay of symmetries, shift vector, and Berry curvature governs the fundamental properties and switching behavior of shift current and circular photocurrent. Ferroicity-driven nonlinear photocurrent switching will open avenues for realizing nonlinear optoelectronics, nonlinear multiferroics, etc., using the coupled ferroic orders and nonlinear responses of ferroic materials under external field.

3D Helix Engineering in Chiral Photonic Materials

Abstract: Engineering the helical structure of chiral photonic materials in three dimensions remains a challenge. 3D helix engineered photonic materials are fabricated by local stratification in a photopolymerizable chiral nematic liquid crystal. The obtained chiral photonic materials reflect both handedness of circular polarized light and show super-reflectivity. Simulations match the experimentally observed photonic properties and reveal a distorted helical structure. 3D engineered polymer films can be made that reflect both left- and right handed circular and linear polarized light dependent and exhibit a changing color contrast upon altering the polarization of incident light. Hence, these 3D engineered photonic materials are of interest for new and emerging applications ranging from anti-counterfeit labels and data encryption to aesthetics and super-reflective films.

Terahertz Vortex Beam as a Spectroscopic Probe of Magnetic Excitations

Abstract: Circularly polarized light with spin angular momentum is one of the most valuable probes of magnetism. We demonstrate that light beams with orbital angular momentum (OAM), or vortex beams, can also couple to magnetism exhibiting dichroisms in a magnetized medium. Resonant optical absorption in a ferrimagnetic crystal depends strongly on both the handedness of the vortex and the direction of the beam propagation with respect to the sample magnetization. This effect exceeds the conventional dichroism for circularly polarized light. Our results demonstrate the high potential of the vortex beams with OAM as a new spectroscopic probe of magnetism in matter.

Broadband Circularly Polarized Planar Monopole Antenna With G-Shaped Parasitic Strip

Abstract: The design of a broadband circularly polarized compact monopole antenna is proposed in this letter. By protruding a G-shaped parasitic strip into a C-shaped monopole antenna structure, two orthogonal modes are created with equal amplitude and 90° phase difference for circular polarization. A 3 dB axial-ratio bandwidth (ARBW) of the antenna is greatly extended by using a modified ground plane. With the help of these features, a compact broadband circularly polarized antenna is designed and fabricated. Experimental results show that the proposed antenna realizes –10 dB impedance bandwidth of 62.94% (3.92–7.52 GHz) and ARBW of 53.92% (4.28–7.44 GHz). Overall size of the proposed monopole antenna is $0.57{\lambda _0} \times 0.61{\lambda _0} \times 0.03{\lambda _0}$ , where ${\lambda _{0\;}}$ is the free-space wavelength at the center frequency of the operating bandwidth. The proposed antenna is desirable for WLAN (5.15–5.85 GHz) applications and various wireless communication systems.

Polarization-Reconfigurable Compact Monopole Antenna With Wide Effective Bandwidth

Abstract: This letter presents a simple microstrip-line-fed wideband polarization-reconfigurable antenna (PRA). A circular metal ring with gaps and modified ground plane is first designed for wideband circular polarization (CP). Two p-i-n diodes are then introduced to control the polarization states. Left-hand CP, right-hand CP, and linear polarization (LP) can be obtained by controlling the biasing state of the diodes. A prototype antenna is fabricated and tested for a C-band application. Measured results show that the antenna achieves a wide effective bandwidth over 3.79–7.82 GHz (both | S 11| ≤ −10 dB and axial ratio ≤ 3 dB) for the CP. However, it decreases to 4.1–6.98 GHz for the LP. Nevertheless, a comparison with previously published PRAs shows that it has the widest effective bandwidth and minimum occupying area.

Ultrafast broadband circular dichroism in the deep ultraviolet

Abstract: The measurement of chirality and its temporal evolution are crucial for the understanding of a large range of biological functions and chemical reactions. Steady-state circular dichroism (CD) is a standard analytical tool for measuring chirality in chemistry and biology. Nevertheless, its push into the ultrafast time domain and in the deep-ultraviolet has remained a challenge, with only some isolated reports of subnanosecond CD. Here, we present a broadband time-resolved CD spectrometer in the deep ultraviolet (UV) spectral range with femtosecond time resolution. The setup employs a photoelastic modulator to achieve shot-to-shot polarization switching of a 20 kHz pulse train of broadband femtosecond deep-UV pulses (250–370 nm). The resulting sequence of alternating left- and right-circularly polarized probe pulses is employed in a pump-probe scheme with shot-to-shot dispersive detection and thus allows for the acquisition of broadband CD spectra of ground- and excited-state species. Through polarization scrambling of the probe pulses prior to detection, artifact-free static and transient CD spectra of enantiopure [Ru(bpy)3]2+ are successfully recorded with a sensitivity of <2×10−5 OD (≈0.7 mdeg). Due to its broadband deep-UV detection with unprecedented sensitivity, the measurement of ultrafast chirality changes in biological systems with amino-acid residues and peptides and of DNA oligomers is now feasible.

Dual-Band Dual-Sense Polarization Reconfigurable Circularly Polarized Antenna

Abstract: This letter presents a novel dual-band circularly polarized slot antenna. The far-field polarization of the antenna can be switched electronically between left-hand circular polarization and right-hand circular polarization. A 50 Ω microstrip feed line is divided into four arms those excite a ground plane slot. The p-i-n diodes are introduced in the arms for polarization switching. A prototype dual-band dual-sense antenna with f 01 = 2.4 GHz and f 02 = 5.2 GHz is fabricated using a 1.6 mm thick FR4 substrate. The measured 3 dB axial ratio bandwidths are more than 16.6% and 5.7% at the lower and upper bands, respectively. The measured return loss is more than 10 dB over the wireless local area network (LAN) bands.

Augmented reality near-eye display using Pancharatnam-Berry phase lenses

Abstract: An augmented reality (AR) near-eye display using Pancharatnam-Berry (PB) phase lenses is proposed. PB phase lenses provide different optical effects depending on the polarization state of the incident light. By exploiting this characteristic, it is possible to manufacture an AR combiner with a small form factor and a large numerical aperture value. The AR combiner adopted in the proposed system operates as a convex lens for right-handed circularly polarized light and operates as transparent glass for left-handed circularly polarized light. By merging this combiner with a transparent screen, such as diffuser-holographic optical elements (DHOEs), it is possible to make an AR near-eye display with a small form factor and a wide field of view. In addition, the proposed AR system compensates the chromatic aberration that occurs in PB phase lens by adopting three-layered DHOEs. The operating principle of the proposed system is covered, and its feasibility is verified with experiments and analysis.

A Polarization-Reconfigurable High-Gain Microstrip Antenna

Abstract: A novel polarization-reconfigurable cut ring microstrip antenna with high gain is proposed. This simple structure microstrip antenna consists of a ring radiation patch, two switches (p-i-n diodes), and six nonmetallic columns. By controlling the switches, the antenna can be operated on three polarized states: one state for linear polarization (LP), one state for left-hand circular polarization (LHCP), and one state for right-hand circular polarization (RHCP). In addition, the antenna peak gain can reach 10.0 dB for LP, LHCP, and RHCP over the operating bandwidth and stable unidirectional radiation patterns. The proposed antenna is fabricated and verified. By analyzing simulated and measured results, the measured common operating bandwidth of the proposed antenna on three states is from 3.86 to 3.98 GHz with the relative bandwidth of 3.1%. The cross-polarization of the antenna on the whole states is very low. Good polarization-reconfigurable characteristics of the proposed antenna have been obtained from 3.86 to 3.98 GHz. The proposed antenna is also a good candidate for advanced wireless communication systems.

Dual-band and high-efficiency circular polarization conversion via asymmetric transmission with anisotropic metamaterial in the terahertz region

Abstract: In this paper, we present an anisotropic metamaterial (AMM) composed of a sub-wavelength metal grating sandwiched with bi-layered double-arrow-shaped (DAS) structure array, which can achieve high-efficiency circular polarization (CP) conversion via giant asymmetric transmission (AT) in terahertz (THz) region. Numerical simulation results indicate that near complete CP conversion with cross-polarization transmission coefficients can reach 0.91 and 0.93, which can be observed at 0.31 and 0.55 THz, respectively. Based on the combination of polarization conversion effects and Fabry-Perot-like cavity-enhanced effect of AMMs, the AT parameter for CP wave can reach a maximum of 0.83 at 0.30 THz, and 0.87 at 0.56 THz, respectively. With appropriate geometric parameters design of each unit-cell, embedded in the proposed AMM, the cross-polarization transmission coefficient and AT parameter for CP waves can be increased to the maximal values of 0.98 and 0.9, respectively. The proposed AMM shows great potential applications in high performance dual-band CP convertor and isolator in THz region.

Generation of Hot Electrons with Chiral Metamaterial Perfect Absorbers: Giant Optical Chirality for Polarization-Sensitive Photochemistry

Abstract: Chiral plasmonic metamaterials have shown very interesting possibilities as chiral optical absorbers for circularly polarized light detection, as their optical response can be manipulated through t...

Controllable linear asymmetric transmission and perfect polarization conversion in a terahertz hybrid metal-graphene metasurface

Abstract: We propose a three layered metal-graphene-metal metasurface to investigate the controllable linear asymmetric transmission and perfect polarization conversion in THz regime, by using the finite-difference time-domain (FDTD) method. An on-to-off control of asymmetric transmission and perfect polarization conversion is achieved by changing the Fermi energy of graphene from 0.8 eV to 0 eV. We present the electric field distribution and Fabry-Perot-like cavity model to analyze the working mechanisms. By gradually shifting the Fermi energy of graphene, two functions are realized, i.e., controllable linear asymmetric transmission and controllable total transmission with near perfect polarization conversion.

Spin-Orbit Interaction of Light in Plasmonic Lattices.

Abstract: In the past decade, the spin-orbit interaction (SOI) of light has been a driving force in the design of metamaterials, metasurfaces, and schemes for light-matter interaction. A hallmark of the spin-orbit interaction of light is the spin-based plasmonic effect, converting spin angular momentum of propagating light to near-field orbital angular momentum. Although this effect has been thoroughly investigated in circular symmetry, it has yet to be characterized in a noncircular geometry, where whirling, periodic plasmonic fields are expected. Using phase-resolved near-field microscopy, we experimentally demonstrate the SOI of circularly polarized light in nanostructures possessing dihedral symmetry. We show how interaction with hexagonal slits results in four topologically different plasmonic lattices, controlled by engineered boundary conditions, and reveal a cyclic nature of the spin-based plasmonic effect which does not exist for circular symmetry. Finally, we calculate the optical forces generated by the plasmonic lattices, predicting that light with mere spin angular momentum can exert torque on a multitude of particles in an ordered fashion to form an optical nanomotor array. Our findings may be of use in both biology and chemistry, as a means for simultaneous trapping, manipulation, and excitation of multiple objects, controlled by the polarization of light.

Information Encoding with Optical Dielectric Metasurfacevia Independent Multichannels

Abstract: Information encryption and security is a prerequisite for information technology, which can be realized by an optical metasurface owing to its arbitrary manipulation over the wavelength, polarization, phase, and amplitude of light. So far information encoding can be implemented by the metasurface in one-dimensional (1D) mode (either wavelength or polarization) only with several combinations of independent channels. Herein, we design dielectric metasurfaces by multiplexing for information encoding in a two-dimensional (2D) mode of both wavelength and polarization. Sixty-three combinations made out of six independent channels by two circular polarization states (RCP and LCP) and three visible wavelengths (633, 532, and 473 nm) are experimentally demonstrated, in sharp contrast with seven combinations by three independent channels in 1D mode. This 2D mode encoding strategy enhances the encryption security dramatically and paves a novel pathway for escalating the security level of information in multichannel ...

Chiral Photonic Cellulose Films Enabling Mechano/Chemo Responsive Selective Reflection of Circularly Polarized Light

Abstract: Stimuli-responsive selective reflection of circularly polarized light in a broad wavelength range is of significance from scientific and technological viewpoints. Herein, chiral photonic cellulose films are fabricated which exhibit selective reflection of circularly polarized light responsive to mechanical and chemical stimuli. The chiral photonic cellulose films are highly deformable with the strain-at-break up to 40.8%, which is the highest among reported chiral photonic cellulose films. Selective reflection of left-handed circularly polarized light responsive to bending and uniaxial tensioning across the entire visible spectrum is demonstrated, as well as reversible response to water vapor (10–100% relative humidity) from the visible to the near-infrared region with Δλ max = 492 nm. The stimuli response is realized by alterable helical organization based on supramolecular chemistry. The current work provides a general strategy for rational design of multistimuli-responsive selective reflection of circularly polarized light, and a soft material platform for scalable camouflaging and security materials.

A Bidirectional Same Sense Circularly Polarized Endfire Antenna Array With Polarization Reconfigurability

Abstract: In this communication, a bidirectional same sense circularly polarized (Bi-SSCP) endfire antenna array with reconfigurable polarization is proposed and implemented. First, a circular polarization (CP) reconfigurable endfire antenna element is realized by adopting two pairs of switchable electric dipoles, which have a 180° phase difference inherently. Along with the fixed magnetic dipole, the endfire antenna element can work at two CP states, i.e., left-hand CP (LHCP) and right-hand CP (RHCP) by switching the states of the two electric dipoles. Then, a Bi-SSCP endfire antenna array with polarization diversity is developed by using two identical endfire antenna elements placed back-to-back with a single feeding probe. For verification, prototypes of the designed endfire antenna element and Bi-SSCP endfire antenna array are fabricated and measured. The measured results show reasonable agreement with the simulated ones. The measured overlapped bandwidth for 10 dB return loss and 3 dB axial ratio of the Bi-SSCP endfire antenna array is from 5.7 to 5.9 GHz for the two CP states.