Polarization Direction Of Light Research Articles

Raman tensor of layered black phosphorus

Black phosphorus has a strong Raman anisotropy on the basal and cross planes due to its orthorhombic crystal structure. However, almost all the studies on black phosphorus’ anisotropy focus on basal plane with the cross plane neglected. Here, we performed a systematic angle-resolved polarized Raman scattering on both the basal and cross planes of black phosphorus and obtained its integral Raman tensors. It is discovered that when the polarization direction of excitation light is along different crystal axes, the Raman intensity ratio (Ixx : Iyy: Izz) of {A}_g^1 mode is 256:1:5. Besides, via calculation, it is confirmed that the strong Raman anisotropy mainly comes from different differential polarizability alone different directions. This phenomenon is also observed when it comes to the {A}_g^2 mode.

Ultracompact metaimage display and encryption with a silver nanopolarizer based metasurface

Governed by the Malus law, nanopolarizer-based metasurfaces can continuously modulate the intensity of incident linearly polarized (LP) light pixel-by-pixel, which has been applied to display metaimages with ultracompactness and high resolution. One unique characteristic of the Malus-assisted image display technique is that no matter the polarization direction of incident LP light, the image with different contrast always appears, which would affect the security of a metaimage. Here, inspired by the orientation degeneracy of the Malus law, we show that metaimage displays can be controlled in two fixed polarization directions, merely by reconfiguring the orientations of nanopolarizers. Specifically, for each metaimage pixel, there are two options for the orientation angle of the nanopolarizer corresponding to an equal grayscale value. By randomly selecting the orientation angle among two choices, the metaimage will be blurred or even hidden, except for the polarization direction of 0° for the original image and 90° for its contrast reversed partners. We experimentally demonstrate this concept by encoding a Lena image with pixels of 1000 × 1000 into a silver nanopolarizer-based metasurface and decoding/encrypting it in a polarization-controlled optical setup. The proposed metaimage display with the encryption functionality has advantages such as continuous grayscale modulation, ultrathinness, and high density, which can be applied in ultracompact image displays, high-end anti-counterfeiting, high-density optical information storage, information encryption, etc.

Polarization tunable color filters based on all-dielectric metasurfaces on a flexible substrate

Structural color filters based on all-dielectric materials are considered to be promising alternatives to metal nanostructures due to significant advantages, such as high-quality resonance effects and low losses of Ohmic effects. We demonstrate a polarization tunable color filter based on all-dielectric metasurfaces, which is based on the arrays of asymmetric monocrystalline silicon nanoblocks on the flexible substrate. By adjusting the physical dimensions of nanoblocks, the filter can exhibit a variety of bright transmission colors. Furthermore, the designed dielectric metasurfaces are sensitive to the linear polarization direction of the incident light, thus a wide range of color images can be created by changing the polarization angles. All of the color filter including the dielectric silicon nanoblocks, the overcladding, and the flexible substrate can be delaminated from the handler substrates and the optical property is reconfigurable, which will find applications in the functional color display, polarization detection and imaging, and secured optical tag.

Broadband, wide-angle, and polarization-insensitive enhancement of light absorption in monolayer graphene over whole visible spectrum

By precise control of the resonance positions of four magnetic dipole modes in metamaterials, we numerically exhibit a broadband light absorption enhancement of monolayer graphene in the whole visible region. In the wavelength range from 450 to 800 nm, the minimum and maximum absorption efficiencies of monolayer graphene exceed 40% and 70%, respectively, and the averaged absorption efficiency can reach as high as about 65%, which suggests great potentials in various optoelectronic devices. Thanks to the localization nature of magnetic dipole modes, the light absorption in monolayer graphene under oblique incidence is, on the whole, less dependent on the incidence angle and the polarization direction of light. Besides ultra-broad bandwidth, other good performances of the light absorption enhancement of monolayer graphene, such as wide incidence-angle and polarization insensitivity, are also desired for graphene-based optoelectronic devices in some cases.

Malus-metasurface-assisted polarization multiplexing

Polarization optics plays a pivotal role in diffractive, refractive, and emerging flat optics, and has been widely employed in contemporary optical industries and daily life. Advanced polarization manipulation leads to robust control of the polarization direction of light. Nevertheless, polarization control has been studied largely independent of the phase or intensity of light. Here, we propose and experimentally validate a Malus-metasurface-assisted paradigm to enable simultaneous and independent control of the intensity and phase properties of light simply by polarization modulation. The orientation degeneracy of the classical Malus’s law implies a new degree of freedom and enables us to establish a one-to-many mapping strategy for designing anisotropic plasmonic nanostructures to engineer the Pancharatnam–Berry phase profile, while keeping the continuous intensity modulation unchanged. The proposed Malus metadevice can thus generate a near-field greyscale pattern, and project an independent far-field holographic image using an ultrathin and single-sized metasurface. This concept opens up distinct dimensions for conventional polarization optics, which allows one to merge the functionality of phase manipulation into an amplitude-manipulation-assisted optical component to form a multifunctional nano-optical device without increasing the complexity of the nanostructures. It can empower advanced applications in information multiplexing and encryption, anti-counterfeiting, dual-channel display for virtual/augmented reality, and many other related fields.

Stable generation of cylindrical vector beams with an all-fiber laser using polarization-maintaining and ring-core fibers.

An all-fiber laser using polarization-maintaining and ring-core fibers that are capable of automatically generating stable TE01 and TM01 modes is proposed and demonstrated experimentally. Two vector-mode coupling long-period fiber gratings (LPFGs) fabricated by a high-frequency CO2 laser are used in the fiber laser to realize efficient coupling between HE11 mode and TE01/TM01 mode. The polarization dependence of the LPFGs is simulated using the coupled-mode theory and verified by experiments. A ring-core fiber is employed to support the stable propagation of TE01 and TM01 modes. By carefully aligning the polarization direction of the input light, the mode coupling ratios of both LPFGs exceed 15 dB. The mode purities of TE01 and TM01 modes are 92.4% and 97.3%, respectively. Owing to the all-polarization-maintaining structure, the laser output is highly stable under environmental disturbance. This laser can be used as a stable cylindrical vector beam source for a wide range of applications, including surface plasmon excitation, optical tweezers, high-resolution metrology and so on.

Investigation on dynamic holographic display in liquid crystal film doped with carbon dots

In this paper, we studied the holographic properties of liquid crystal (LC) thin film doped with carbon dots (CDs) which can be used as real-time holographic display screen. The maximum value of diffraction efficiency can reach up to 30% by using a low applied electric field 0.2 V/μm. Holograms in the LC film can be dynamically formed and self-erased. The hologram build-up time and the hologram self-erasure time in the material is fast enough to realize video refresh rate. In addition, the forming process of hologram was studied. The holographic diffraction efficiency was measured depending on the intensity of recording light, applied electric field, the intensity of readout light, and readout light polarization direction. Triple enhancement of the diffraction efficiency value by the modulation of voltage under the condition of low recording energy is presented. Therefore, we develop an easy way to obtain real-time dynamic holographic red, green and blue displays with high diffraction efficiency, which allow the LC film doped with CDs to be used as a holographic 3D display screen.

Chiral quantum optics in photonic sawtooth lattices

Chiral quantum optics has become a burgeoning field due to its potential applications in quantum networks or quantum simulation of many-body physics. Current implementations are based on the interplay between local polarization and propagation direction of light in nanophotonic structures. In this manuscript, we propose an alternative platform based on coupling quantum emitters to a photonic \emph{sawtooth} lattice, a one-dimensional model with an effective flux per plaquette introduced by complex tunnelings. We study the dynamics emerging from such structured photonic bath and find the conditions to obtain quasi-perfect directional emission when the emitters are resonant with the band. In addition, we find that the photons in this bath can also mediate complex emitter-emitter interactions tunable in range and phase when the emitters transition frequencies lie within a band-gap. Since these effects do not rely on polarization they can be observed in platforms beyond nanophotonics such as matter-waves or circuit QED ones, of which we discuss a possible implementation.

Rashba spin-orbit coupling enhanced two-photon absorption and its polarization dependence in monolayer black phosphorus

We investigate theoretically the impact of Rashba spin-orbit coupling (RSOC) effect to two-photon absorption (TPA) and its dependence on the polarization direction of the incident light in monolayer black phosphorus (BP) starting from an anisotropic two band k·p model. It is found that the TPA is enhanced several times by RSOC effect which is tuned by the external electric field. And the TPA response shows highly anisotropic, changing periodically with the polarization direction of incident linearly polarized light as the function of cos4θ approximatively. The TPA coefficient reaches its maximum when the polarization direction is aligned along the armchair direction (x-direction), while falls into its minimum along the zigzag direction (y-direction).

Volatile and permanent optical gratings recorded in Bi2TeO5 photorefractive crystal under high cw intensity

We report the recording of optical gratings on photorefractive $ {{\rm Bi}_2}{{\rm TeO}_5} $Bi2TeO5 crystals using $ \lambda = 532\,\,{\rm nm} $λ=532nm wavelength light. We studied the behavior of this material under high light intensity and found the presence of fast and slow gratings, both of photorefractive nature and exhibiting quite significant light intensity dependence for the $ 1 - 13\,\,{\rm kW}/{{\rm m}^2} $1-13kW/m2 range. A permanent grating was found after the complete erasure of fast and slow holograms recorded at room temperature. The experimental results show that the diffraction efficiency of the permanent grating increases with the recorded light intensity. The permanent grating performance as an optical Bragg filter was characterized by measuring the angular selectivity approximately 1.0 mrad. We also show that the diffraction efficiency of the permanent grating is quite dependent on the direction of light polarization.

Polarization independent double-band electromagnetically induced transparency effect in terahertz metamaterials

In this article, we experimentally and numerically investigated a metamaterial (MM) geometry capable of exhibiting polarization independent double-band electromagnetic induced transparency (EIT) effect. The meta-molecule unit of the proposed MM configuration composed of a strip and two asymmetric split ring resonators (SRRs). For polarization independent double-band EIT effect, the existing meta-molecule unit is converted into a cross-like structure adorned with four SRRs. Terahertz transmission response is analyzed for two orthogonal polarization directions of the incident light to confirm the polarization independent response. In order to understand and explain our numerical findings more elaborately we have employed four-level tripod atomic system based analytical model. The transmission response is also analyzed for different angle of incidence of the two orthogonal polarizations. In order to demonstrate the practical applicability of our study, we have studied the effect of transmission with the change of refractive index of analyte of thickness 10 μm coated on the top of the MM resonators. The calculated sensitivities for the 1st, 2nd and 3rd dips are 121 GHz/RIU, 138 GHz/RIU and 135 GHz/RIU (RIU, refractive index unit) respectively. Our study can also play an important role in the advancement of slow light devices, modulators and filters.

Polarization and direction-controlled asymmetric multifunctional metadevice for focusing, vortex and Bessel beam generation.

Integrating multiple independent functionalities into one single photonic device has been an important part in optoelectronic system. In this paper, we here propose a kind of asymmetric multifunctional metadevice operating at 1550 nm (in optical communication band), which can manipulate the light with four different functions, depending on the polarization and illumination direction of incident light. As a proof of our concept, we design this metadevice composed of the upper metasurface layer, middle grating layer and lower metasurface layer. For x-polarized incident light, the metadevice under forward illumination works as transmissive focusing lens and vortex beam generator of y-polarized light, while under backward illumination it acts as a reflective vortex beam generator. In contrast, for y-polarized incident light, the metadevice under forward illumination behaves as a reflective Bessel beam generator, while a combination of transmissive vortex beam generator and focusing lens of x-polarized light under backward illumination. Our findings may motivate the realization of high-performance multifunctional metadevices and extend the application in complex integrated optical system.

Effect of electric field on optoelectronic properties of indiene monolayer for photoelectric nanodevices

In recent years, layered materials display interesting properties and the quest for new sorts of two-dimensional (2D) structures is a significance for future device manufacture. In this paper, we study electronic and optical properties of 2D indiene allotropes with planar and buckled structures. The optical properties calculations are based on density functional theory (DFT) simulations including in-plane and out-of-plane directions of light polarization. We indicate that the optical properties such as complex refractive index, absorption spectrum, electron energy loss function (EELS), reflectivity and optical conductivity spectra are strongly dependent on the direction of light’s polarization. High values and narrow peaks in optical spectra introduce indiene to the field of ultra-thin optical systems. The effect of external static electric field on electronic and optical properties of indiene is also observed and discussed. We show that the band gap in buckled indiene can be effectively changed by applying the external electric field. The discoveries here expand the group of 2D materials beyond graphene and transition metal dichalcogenides (TMDs) and give valuable data for future experimental realization of new mono-elemental materials with conceivable applications in optical devices.

Manipulating birefringence in AgCl thin film loaded by silver nanoparticles under normal and oblique incident angles

We have induced anisotropy in AgCl thin film, which is loaded by silver nanoparticles, by irradiating a single low power laser beam at wavelength 532 nm. The induced anisotropy in Ag–AgCl thin film is due to the formation of gratings in the direction of light polarization for both normal and oblique angles of laser incidence. In Ag–AgCl thin film, which was irradiated by oblique laser beam, complex grating with different line-spaces is formed. It turns out that the line-spaces of the grating depend on the incident angle. Therefore, by changing the incident angle of the laser beam, the morphology and optical properties of anisotropic nanostructures formed on Ag–AgCl thin film can be manipulated. Linear birefringence and linear dichroism are measured in these nanostructures by probe beams at different wavelengths in the visible region. Our results show that the sample which is irradiated normally has the largest linear birefringence and linear dichroism compared to the oblique incident samples. In the normal incident sample, the maximum value of linear birefringence is seen at wavelength 632.8 nm (Δn = 0.35), while the largest absolute value of linear dichroism is observed at wavelength 532 nm, which is the same wavelength as the incident laser beam.

Spin polarized electronic and optical properties of vacancy defects in armchair phosphorene nanoribbons

Using first-principles density functional theory, spin dependent electronic and optical properties of Armchair Phosphorene Nanoribbons (APNRs) with different widths (W = 8, 9, 10, 11) are investigated in presence of vacancy defects including of SV1, SV2, DV1, DV2 and DV3. The results show that geometric structures of APNRs, type and position of defects are essential factors in determining the electronic, magnetic and optical properties of APNRs. It is observed that 8, 9, 10 and 11APNRs in presence of the SV1 or SV2 defects are magnetic. However, DV1, DV2 and DV3 in APNRs with different widths can lead to non magnetic semiconductor with direct or indirect band gap. In addition, the effect of various defects concentrations (C = 1.38, 1.13 and 0.92%) is studied on the electronic and optical properties of 9APNR. The results show that the value of defect concentration can tune the electronic, magnetic and optical properties of 9APNRs. In all considered systems, the optical properties exhibit the strong anisotropic behaviors with respect to direction of light polarization. All these theoretical observations would open up possibilities for applications of APNRs in spintronic and optoelectronic devices.

From Strong Dichroic Nanomotor to Polarotactic Microswimmer.

Light-driven micro/nanomotors are promising candidates for long-envisioned next-generation nanorobotics for targeted drug delivery, noninvasive surgery, nanofabrication, and beyond. To achieve these fantastic applications, effective control of the micro/nanomotor is essential. Light has been proved as the most versatile method for microswimmer manipulation, while the light propagation direction, intensity, and wavelength have been explored as controlling signals for light-responsive nanomotors. Here, the controlling method is expanded to the polarization state of the light, and a nanomotor with a significant dichroic ratio is demonstrated. Due to the anisotropic crystal structure, light polarized parallel to the Sb2 Se3 nanowires is preferentially absorbed. The core-shell Sb2 Se3 /ZnO nanomotor exhibits strong dichroic swimming behavior: the swimming speed is ≈3 times faster when illuminated with parallel polarized light than perpendicular polarized light. Furthermore, by incorporating two cross-aligned dichroic nanomotors, a polarotactic artificial microswimmer is achieved, which can be navigated by controlling the polarization direction of the incident light. Compared to the well-studied light-driven rotary motors based on optical tweezers, this dichroic microswimmer offers eight orders of magnitude light-intensity reduction, which may enable large-scale nanomanipulation as well as other heat-sensitive applications.

Measuring the Three-Dimensional Volume Scattering Functions of Microsphere Suspension: Design and Laboratory Experiments

The measurement of the volume scattering function (VSF) of suspended particles is an ongoing research topic since it has the potential to provide a rapid, nondestructive means of analyzing hydrosols. Despite the success of scattering theory, the measurement of multidirectional scattering intensity distributions over a wide, continuous range of scattering angles and multiple scattering planes, which is described by a three-dimensional VSF (3D VSF), has proven to be difficult. To measure the 3D VSF of submicron particles suspended in water, a measurement approach is proposed, built and tested with several standard submicron particles with diameters ranging from 60 nm to 1 μm. The experimental results indicate that the proposed setup can obtain an accurate 3D VSF for scattering angles from 21° to 160° and azimuthal angles from 1° to 179°. Comparisons between the experiment and theory show a high level of consistency for particles with diameters less than 200 nm. The variation in the VSF in response to the polarization direction of the incident light is also discussed. Both the experiment and theory show the potential of the device to detect the 3D VSF of marine submicron biological particles.

Photocontrollable Deformations of Polymer Particles in Elastic Matrix

AbstractOne of the key challenges of material science currently is the design of multifunctional “smart” materials combining features from both molecular and supramolecular levels. Pursuing the strategy of amplification and transduction of light‐induced motion of small molecules (photoswitches) across increasing length scales to macroscopic level, a novel polymer composite based on shape‐reconfigurable microparticles is designed. The composite represents soft elastic matrix filled with photoactive microparticles of liquid crystal (LC) polymer bearing azobenzene moieties. Illumination of the composite film with polarized light results in a dramatic deformation of the microparticles such that the initially spherical shape becomes elongated along the direction of light polarization. This shape‐shifting of particles is fully reversible and can be achieved by annealing or exposure to nonpolarized light. It is shown that photodeformation of particles is accompanied by photo‐orientation of LC molecules and both processes can be controlled independently. The practical relevance of such materials is pointed out by the possibility to control optical properties (birefringence and light scattering) and optomechanical feedback yielding a new class of photoactuators. Overall, the developed material containing microscopic polymer photoactuators demonstrates an effective way of transducing molecular operation towards macroscopic functionality and can be particularly useful for optics and soft‐robotics.

Dichroic Plasmon Superstructures of Au Nanorods over Macroscopic Areas via Directed Self‐Assemblies of Diblock Copolymers

AbstractThe ability to organize metal nanoparticles over the macroscopic length scale has fundamental implications for advanced plasmonic applications. In particular, linear assemblies of anisotropic nanorods (NRs) may represent a dichroic superstructure, in which plasmonic extinction is inherently dependent on the direction of light polarization. As plasmonic properties are interconnected with optics, electronics, catalysis, and sensing, dichroism in plasmonic systems can stimulate interesting opportunities in many fields of chemistry. However, the preparation of dichroic structures with a single orientation at the centimeter scale remains a significant challenge. Herein, directed self‐assemblies of polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) diblock copolymers on lithographical patterns are applied to produce a linear pattern of Au NRs. Periodic nanogrooves from plasma‐etched PS‐b‐PMMA nanodomains facilitate the dense packing of Au NRs into end‐to‐end alignment, which entail strong plasmonic coupling among longitudinal plasmonic modes. Because the resulting NR assemblies have uniform orientation, their dichroic functions can be examined by conventional UV–vis spectroscopy without the aid of single‐particle measurements. Interestingly, both transverse and longitudinal localized surface plasmonic resonance peaks can be turned on and off under two polarized lights in orthogonal directions. Moreover, the resulting superstructures can be transferred onto various substrates, allowing the implantation of dichroic functions for numerous plasmonic applications.

Subsurface Damage Detection on Ground Silicon Wafers Using Polarized Laser Scattering

Abstract A silicon wafer is important for the electronic and computer industries. However, subsurface damage (SSD), which is detrimental to the performance and lifetime of a silicon chip, is easily induced in a silicon wafer during a grinding process since silicon is typically a hard and brittle material. Therefore, it is necessary to detect and remove SSD in the subsequent processes. In this study, a polarized laser scattering (PLS) system is installed to detect the SSD in a ground wafer. It is found that not only the subsurface crack but also the residual stress leads to depolarization of an incident light. The effects of residual stress on depolarization are studied. The residual stress results in the photoelasticity, which causes the depolarization of the incident light in the PLS system. The depolarization caused by the residual stress is determined by the directions and the difference of the principal stresses. When the polarization direction of the incident light is aligned with one of the principal stresses, the effects of the residual stress can be minimized; therefore, the subsurface crack can be quantitatively estimated by PLS.