Orthogonal Linear Polarization States Research Articles

Metasurface-Based Optical Logic Operators Driven by Diffractive Neural Networks.

In this paper, a novel optical logic operator based on the multifunctional metasurface driven by all-optical diffractive neural network is reported, which can perform four principal quantum logic operations (Pauli-X, Pauli-Y, Pauli-Z, and Hadamard gates). The two ground states and are characterized by two orthogonal linear polarization states. The proposed spatial- and polarization-multiplexed all-optical diffractive neural network only contains a hidden layer physically mapped as a metasurface with simple and compact unit cells, which dramatically reduces the volume and computing resources required for the system. The designed optical quantum operator is proven to achieve high fidelities for all four quantum logical gates, up to 99.96% numerically and 99.88% experimentally. The solution will facilitate the construction of large-scale optical quantum computing systems and scalable optical quantum devices.

Spintronic terahertz polarization programmable system for information encoding

Terahertz (THz) wave as an important electromagnetic wave has been increasingly applied in wireless communication and imaging sensing technology. It has been an increasingly practical application. Ultra-high data rates in communication technology push toward a broadband, controllable polarization, and multiple transmission channels signal sources. Here, we propose a programmable polarization spintronics terahertz source (PP-STS), in which contains a controllable polarization spintronic THz emitter and a microcontroller unit. The PP-STS not only can generate THz waves with wide frequency bandwidth, but also has the function of switching the orthogonal linear polarization state of the generated THz waves flexibly. By coding the microcontroller unit, the designed PP-SPS can directly program the orthogonal linear polarization states as a series of information to transmit. To achieve the interconversions between digital codes and the THz polarization information, an optimum matching THz polarization beam splitter (THz-PBS) is also designed via simulations and experiments. The THz-PBS, as a decoder, can accurately split the transverse electric (TE) and transverse magnetic (TM) modes into two THz detectors. At last, a coding and decoding prototype system of spintronic THz polarization is built by integrating the PP-STS, the THz-PBS and two THz detectors. The send and receive information with high speed and accuracy are verified in this prototype system as well. We believe that our work takes THz applications for multiplexing communications one step further and sheds light on commercializing the PP-STS with exciting manufacturing lines for efficient and economical THz polarization technology.

High-Q guided-mode resonance of a crossed grating with near-flat dispersion

Guided-mode resonances in diffraction gratings are manifested as peaks (dips) in reflection (transmission) spectra. Resonances with smaller line widths, i.e., with higher Q-factors, ensure stronger light–matter interactions and are beneficial for field-dependent physical processes. However, these high-Q resonances often suffer from strong angular and spectral dispersions. We demonstrate that a class of resonant modes with extraordinarily weak dispersion and Q-factor ∼1000 can be excited in crossed gratings simultaneously with the modes with well-known linear dispersion. Furthermore, the polarization of the incoming light can be adjusted to engineer the dispersion of these modes, and strong to near-flat dispersion or vice versa can be achieved by switching between two mutually orthogonal linear polarization states. We introduce a semi-analytical model to explain the underlying physics behind these observations and perform full-wave numerical simulations and experiments to support our theoretical conjecture. The results presented here will benefit all applications that rely on resonances in free-space-coupled geometries.

Adding/dropping polarization multiplexed cylindrical vector beams with local polarization-matched plasmonic metasurface.

Here we propose a polarization-dependent gradient phase modulation strategy and fabricate a local polarization-matched metasurface to add/drop polarization multiplexed cylindrical vector beams (CVBs). The two orthogonal linear polarization states in CVB multiplexing will represent as radial- and azimuthal-polarized CVBs, which means that we must introduce independent wave vectors to them for adding/dropping the polarization channels. By designing the rotation angle and geometric sizes of a meta-atom, a local polarization-matched propagation phase plasmonic metasurface is constructed, and the polarization-dependent gradient phases were loaded to perform this operation. As a proof of concept, the polarization multiplexed CVBs, carrying 150-Gbit/s quadrature phase shift keying signals, are successfully added and dropped, and the bit error rates approach 1 × 10-6. In addition to representing a route for adding/dropping polarization multiplexed CVBs, other functional phase modulation of arbitrary orthogonal linear polarization bases is expected, which might find potential applications in polarization encryption imaging, spatial polarization shaping, etc.

Configuring Polarization Singularity Array Composed of C-Point Pairs

The generation and topological configuration of double-layered polarization singularity array (PSA) having paired C-points of opposite topological index through superposing three Laguerre-Gaussian (LG) component beams with orthogonal linear polarization states are demonstrated. The generated PSA beam exhibits diversity in topological geometry and intensity pattern. The topological rule that the zero net topological charge and helicity conservation hold for the entire PSA is also confirmed. Based on our experiment setup consisting of a computer-controlled spatial light modulator (SLM), the PSA morphology can be flexibly customized and dynamically regulated by modulating the parameters of constituent beams. Our scheme provides a convenient device for manipulating polarization singularities and can facilitate the potential applications of singular optics.

Polarization-dependent photonic crystal fiber optical filters enabled by asymmetric metasurfaces

Abstract We demonstrate in-fiber polarization-dependent optical filter by nanopatterning an asymmetric metallic metasurface array on the end-facet of polarization-maintaining photonic-crystal fibers. The asymmetric cross-typed nanoslit metasurface arrays are fabricated on the core of the optical fiber using the focused ion beam milling technique. Highly polarization- and wavelength-dependent transmission with transmission efficiency of ∼70% in the telecommunication wavelength was observed by launching two orthogonal linear-polarization states of light into the fiber. Full-wave electromagnetic simulations are in good agreement with the experimental results. These advanced meta-structured optical fibers can potentially be used as novel ultracompact in-fiber filters, splitters, and polarization converters.

Broadband Efficient Dual‐Polarization Airy Beam Generation with Reflective Metasurface

This study demonstrates that continuous amplitude and binary phase modulation suitable for Airy beam encoding can be frequency‐independently obtained with not only cross‐polarized but also copolarized transmitted/reflected electromagnetic field components by rotation of unit cell with reflection symmetry. Maximum device efficiency can be achieved with relevant Airy beam generator, when the eigen polarization states of the unit cell are two orthogonal linear polarization states, and the copolarization reflections of them are out of phase and both have the amplitude of unity. As a proof of principle, broadband and high‐efficiency reflective Airy beam generators based on both copolarization and cross‐polarization modulation approaches are fabricated with cut‐wire structure as unit cell. The measured results show that the efficiency of the devices is approaching the theoretical limit in a wide frequency range.

A Parasitic Antenna with Independent Pattern, Beamwidth and Polarization Reconfigurability

In this paper, a reconfigurable antenna design is proposed to realize independent pattern, beamwidth and polarization reconfiguration at an operating frequency of 2.45 GHz. This antenna is comprised of a dual coaxial-feed driven element surrounded by four varactor loaded size-tunable parasitic elements. The pattern and beamwidth reconfiguration is achieved by utilizing the mutual coupling between the active and size-tunable parasitic elements. Reconfigurable feeding network is designed and developed to produce two orthogonal linear polarization (LVP, LHP) and circular polarization (LHCP, RHCP) states. In linear polarization operating mode, main beam of the antenna is continuously scanned from $$\theta$$ = 0 $$^{\circ }$$ to 11 $$^{\circ }$$ , 0 $$^{\circ }$$ to 32 $$^{\circ }$$ , and 0 $$^{\circ }$$ to 40 $$^{\circ }$$ in $$\phi$$ = ±0 $$^{\circ }$$ , ± 45 $$^{\circ }$$ , and ± 90 $$^{\circ }$$ plane respectively, where $$\theta$$ and $$\phi$$ are the beam direction in the elevation and azimuth planes respectively. In circular polarization operating mode, the radiated beam is continuously scanned from 0 $$^{\circ }$$ to 30 $$^{\circ }$$ in $$\phi$$ = ± 0 $$^{\circ }$$ , ± 45 $$^{\circ }$$ and ± 90 $$^{\circ }$$ plane respectively with axial ratio less than 3 dB in all the beam scanning directions. In addition to this, 3-dB beamwidth is continuously tuned in the E-plane, H-plane, and both E-plane and H-plane with LVP and LHP operating mode from 66 $$^{\circ }$$ to 152 $$^{\circ }$$ , 60 $$^{\circ }$$ to 108 $$^{\circ }$$ , and 78 $$^{\circ }$$ to 120 $$^{\circ }$$ respectively.

A highly sensitive imaging polarimeter in the x-ray regime

We report on the development of a highly sensitive imaging polarimeter that allows for the investigation of polarization changing properties of materials in the x-ray regime. By combining a microfocus rotating anode, collimating multilayer mirrors, and two germanium polarizer crystals, we achieved a polarization purity of the two orthogonal linear polarization states of 8 × 10−8. This enables the detection of an ellipticity on the same order or a rotation of the polarization plane of 6 arcsec. The high sensitivity combined with the imaging techniques allows us to study the microcrystalline structure of materials. As an example, we investigated beryllium sheets of different grades, which are commonly used for fabricating x-ray lenses, with a spatial resolution of 200 μm, and observed a strong degradation of the polarization purity due to the polycrystalline nature of beryllium. This makes x-ray lenses made of beryllium unsuitable for imaging polarimeter with higher spatial resolution. The results are important for the development of x-ray optical instruments that combine high spatial resolution and high sensitivity to polarization.

Deterministic aperiodic photonic crystal with a 2D array of metallic nanoparticles as polarization-sensitive dichroic filter

We demonstrate the possibility of using a two-dimensional array of spheroidal metallic nanoparticles embedded in a one-dimensional photonic crystal to obtain a narrow-bandpass, polarization-sensitive dichroic filter operating in the near-UV and visible domains. The optical anisotropy of the array of identically oriented nanoparticles results in two spectrally distinct plasmon resonances independently excited for two mutually orthogonal linear polarization states of light, which ensures polarization and spectral selectivity of the composite structure. The narrow transmission bands of the filter are defect modes due to a layer located at the center of the structure and hosting the nanoparticle array. In order to suppress these transmission windows, it is essential that the defect modes closely coincide with the plasmon resonances excited in the array. We show that the use of deterministic aperiodic distributed reflectors surrounding the defect layer makes it possible to adjust the spectral positions of two defect modes in two separate bandgaps in order to achieve such a coincidence. Among the various parameters governing the precise position of transmittivity windows of the filter, we establish the strong influence of the thickness of the defect layer. We also show that a strong localization of the optical field in the plane of the nanoparticle array is essential to enhance the efficiency of plasmonic excitation and obtain the desired control of the defect modes. Our study opens up possibilities for the further development of polarization-controlled nanophotonic devices.

A novel filter wheel for multi-channel switching and polarization rotation

This study proposes an innovative filter wheel for the multi-channel switching of polarization state. The proposed device enables switching between two orthogonal linear polarization states or two orthogonal circular polarization states to achieve either linear dichroism (LD) or circular dichroism (CD). The filter wheel enables channel switching and orientation rotation with high repeatability. This paper describes in detail the methods used in the alignment of multiple polarizers and quarter-waveplates. In addition, the extinction ratio and retardation, which can be used as indications of polarimetric performance, are measured to a high degree of precision. The apparatus was applied for 6-channel polarization state switching in which three channels were used for multi-spectral broadband polarimetric applications across a range of 400–1600 nm. The remaining three channels were used for multi-wavelength precision polarimetric applications at wavelengths of 457, 532, and 632 nm in the visible range. When installed in a microspectrophotometer, the proposed apparatus can be used in multi-spectral broadband polarimetric spectroscopy as well as multi-wavelength polarimetric imaging applications to achieve LD and CD effects at the micro scale.

Systematic error cancellation for a four-port interferometric polarimeter

The Primordial Inflation Explorer (PIXIE) is an Explorer-class mission concept to measure the gravitational-wave signature of primordial inflation through its distinctive imprint on the linear polarization of thecosmic microwave background (CMB). Its optical system couples a polarizing Fourier transform spectrometerto the sky to measure the differential signal between orthogonal linear polarization states from two co-pointedbeams on the sky. The double differential nature of the four-port measurement mitigates beam-related systematic errors common to the two-port systems used in most CMB measurements. Systematic errors coupling unpolarized temperature gradients to a false polarized signal cancel to first order for any individual detector. Thiscommon-mode cancellation is performed optically, prior to detection, and does not depend on the instrumentcalibration. Systematic errors coupling temperature to polarization cancel to second order when comparing signals from independent detectors. We describe the polarized beam patterns for PIXIE and assess the systematicerror for measurements of CMB polarization.

P‐85: Multiview Full‐Resolution Autostereoscopic Imaging with Alternating Polarization‐Coded Image Pairs: Front Active Amplitude Parallax Barrier and Rear Passive Polarization Parallax Barrier

The proposed autostereoscopic method allows to reproduce K view images (each with full‐screen resolution) in K observation zones with a K/2‐fold increase of a frame rate in compare with the standard 60 Hz frame rate (where K≥4). For example, the 4‐view stereoscopic flicker‐free image can be formed at 120 Hz (or the 8‐view image at 240 Hz) frame rate. The characteristic property of the layout is the performance of the image forming matrix with input light having two mutually orthogonal states of linear polarization.

Wideband Quad-Polarization Reconfigurable Antenna Using Switchable Feed Network With Stable Unidirectional Radiation Patterns

A wideband antenna with quad-polarization reconfigurable operation is proposed. It consists of a crossed tri-port feed linearly polarized (LP) radiation structure and a switchable feed network. A dual-port LP element with wideband characteristic and good port isolation is first introduced. The inherent 180° phase difference (PD) between two feed ports vastly simplifies the complexity of the design and improves the efficiency of the feed network. By assembling two grooved LP elements, the crossed tri-port feed radiation structure is formed. Meanwhile, a wideband 90° phase shifter and an unequal Wilkinson power divider are applied in designing the switchable feed network. Through controlling the PIN diodes implanted in the feed line, four working modes with equal amplitude and reconfigurable PD (0° or 90°) are achieved. Based on this, the desired quad-polarization reconfiguration, including two orthogonal linear polarization (LP) states and two orthogonal circular polarization (CP) states, is realized. Measured results show that the proposed antenna has a wide overlapped operation impedance bandwidth of 84.5%, ranging from 1.36 ~ 3.35 GHz, for all polarization states within a compact volume. The measured 3-dB AR bandwidth is 100%, covering the operation impedance frequency range. Radiation patterns exhibit unidirectional and stable quality from the point view of beam slant and split. Besides, a peak efficiency of 75% and a peak gain of 7.8 dBi are achieved.

Luminescent hyperbolic metasurfaces

When engineered on scales much smaller than the operating wavelength, metal-semiconductor nanostructures exhibit properties unobtainable in nature. Namely, a uniaxial optical metamaterial described by a hyperbolic dispersion relation can simultaneously behave as a reflective metal and an absorptive or emissive semiconductor for electromagnetic waves with orthogonal linear polarization states. Using an unconventional multilayer architecture, we demonstrate luminescent hyperbolic metasurfaces, wherein distributed semiconducting quantum wells display extreme absorption and emission polarization anisotropy. Through normally incident micro-photoluminescence measurements, we observe absorption anisotropies greater than a factor of 10 and degree-of-linear polarization of emission >0.9. We observe the modification of emission spectra and, by incorporating wavelength-scale gratings, show a controlled reduction of polarization anisotropy. We verify hyperbolic dispersion with numerical simulations that model the metasurface as a composite nanoscale structure and according to the effective medium approximation. Finally, we experimentally demonstrate >350% emission intensity enhancement relative to the bare semiconducting quantum wells.

Single-Photon Emission of a Hydrogenlike Atom

Implementing a previously obtained, original solution of the Dirac equation for an electron in the field of a nucleus (Ze) expressed in terms of the wave function of the corresponding Schrodinger equation and its derivatives in spherical coordinates and the spin projection operator Σ3 associated with the eigenfunction, taking into account in each component of the spinor the leading term of the expansion in the small parameter (Zα), α = e 2 / ħc ≈ 1 / 137, the partial probabilities W of emission of a photon (Zα)* → (Zα) + γ have been calculated. Here two orthogonal states of the linear polarization of the photon, and also the spin states of the electron, which previously had not been taken into consideration, have been taken into account in the transverse gauge. It turns out that the probabilities W of emission of a photon per unit time for any allowed transitions are proportional to (Zα)4, as was previously accepted, and the selection rules for the quantum number m have the usual form ∆m = 0,±1. It was found that a spin flip does not take place during emission. In contrast to the customary situation with the selection rules for the quantum number l being of the form ∆l = ±1, for ∆m = ±1 there also exist integrals over dcosθ which are not equal to zero for undetermined odd values of ∆l. In this, and also in a fundamentally different dependence of the amplitude on the quantum numbers consist the differences from the traditional approach to the problem. Necessary conditions are formulated, under the fulfillment of which the selection rules for l are not changed, having values ∆l = ±1 for arbitrary ∆m, but it was not possible, however, to give a complete proof of these rules.

Vacuum ultraviolet spectropolarimeter design for precise polarization measurements.

Precise polarization measurements in the vacuum ultraviolet (VUV) region provide a new means for inferring weak magnetic fields in the upper atmosphere of the Sun and stars. We propose a VUV spectropolarimeter design ideally suited for this purpose. This design is proposed and adopted for the NASA-JAXA chromospheric lyman-alpha spectropolarimeter (CLASP), which will record the linear polarization (Stokes Q and U) of the hydrogen Lyman-α line (121.567nm) profile. The expected degree of polarization is on the order of 0.1%. Our spectropolarimeter has two optically symmetric channels to simultaneously measure orthogonal linear polarization states with a single concave diffraction grating that serves both as the spectral dispersion element and beam splitter. This design has a minimal number of reflective components with a high VUV throughput. Consequently, these design features allow us to minimize the polarization errors caused by possible time variation of the VUV flux during the polarization modulation and by statistical photon noise.

Near video-rate linear Stokes imaging with single-pixel detectors

In this work we demonstrate a polarization sensitive computational imaging system based on a digital micro-mirror device (DMD) and several single-pixel photodetectors. By taking advantage of computational imaging techniques, the light measured by each single-pixel detector can reconstruct a 2D image for a specific linear polarization state. Using the rapid frame-rate of the DMD to continuously project a series of spatially orthogonal illumination patterns, near video-rate reconstructions can be achieved. In addition we extend this approach to provide full-colour images through a process of sequential colour selection (RGB). Taking the difference between photodetector signals from orthogonal linear polarization states, we obtain images corresponding to the linear Stokes parameters. We apply this rapid polarization sensitive imaging system to inert and biological material. Since the spatial information in the images reconstructed by this approach are determined by the projection system, rather than the detectors, the approach provides perfect pixel registration between the various polarization selective images and associated Stokes parameters. Furthermore, the use of single-pixel detectors and the large operational bandwidth afforded by DMDʼs means that the approach can readily be extended for imaging at wavelengths where detector arrays are unavailable or limited.

Polarization dependent color switching by extra-ordinary transmission in H-slit plasmonic metasurface

An array of H-shaped subwavelength slits in a plasmonic film has a polarization dependent extra-ordinary transmission due to shape anisotropy. Non-overlapping extra-ordinary transmission bands for the orthogonal linear polarization states of the input light are used to demonstrate a polarization dependent color switch. The fabricated array of submicron sized H-slits on a gold film displayed two transmission bands for the linear x- and y-polarized light at visible (650–850 nm) and near-infra-red (1150–1450 nm) bands, respectively. The relative transmitted light in these two bands can be controlled by changing the linear polarization state of the input radiation from 0° to 90°.

Polarization Jitters Caused by Fiber Nonlinearity in PM Optical Communication System

The phenomenon of polarization jitters caused by fiber nonlinearity is investigated. A general formula about the polarization jitter is concluded in polarization multiplexing (PM) system based on two orthogonal linear polarization states when the best polarization correction is used. A 100 Gb/s PM system based on NRZ code is investigated by simulation, and the Stocks parameter about polarization jitter and Poincare sphere diagrams are got for different power and phase difference of two orthogonal polarized light. The results show that the polarization jitters will be suppressed when the combined PM signal is the linear or circular polarization state.