Ideal Polarization Research Articles

The Effect of Crystal Contact Forces on the Protein Global Motions

Protein crystals are widely used for structural determination using X-ray crystallography and solid state NMR. X-ray free electron lasers have enabled direct dynamical structural movies of photo or chemically initiated biochemical reactions. However the perturbation of protein dynamics by the crystal contact forces has been persistently under debate. If crystal contact forces are sufficiently strong, the time resolved X-ray diffraction measurements will not accurately reflect the in vivo biological dynamics. Here we probe the effect of crystal contact forces on protein structural dynamics by directly measuring the collective intramolecular vibrations as a function of crystal symmetry for chicken egg white lysozyme (CEWL). These vibrations extend throughout the protein, involving coherent motion of entire domains. While the collective vibrational density of states is a broad continuous spectrum peaked near 100 cm−1, (3 THz), polarization dependent terahertz absorption isolates vibrations with displacements primarily along the polarization direction [1]. Triclinic, monoclinic, tetragonal and orthorhombic CEWL crystals are grown according to previous published protocols. X-ray measurements verify their crystal structure and quality before and after terahertz measurements. The anisotropic terahertz absorbance is measured using our new technique: ideal polarization varying anisotropic THz microscopy (IPV-ATM). This near field THz microscopy method allows rapid determination of the anisotropic THz absorption. By starting from measurements of the lowest symmetry, triclinic crystals, which have a single protein per unit cell and absolute alignment of the protein molecule array, we can predict the spectra for higher symmetry groups, neglecting crystal contact perturbations. We compare our predicted spectra to the measurements of the monoclinic, orthorhombic and tetragonal crystals, attaining a measure of the impact of the intermolecular crystal forces on the intramolecular vibrations. [1]G. Acbas, K. A. Niessen, E. H. Snell, and A. G. Markelz, Nat. Comm.(2014) https://doi.org/10.1038/ncomms4076.

Application of Scale of Absolute Surface Potentials to the Reactions of Chemisorption and Electrocatalysis on Metals. Part 2

The concepts of the absolute surface potential (ASP) ES of the (hkl) facet of a metal crystal with ES = ΔGs/zF directly related to the Gibbs surface energy ΔGS and with an equilibrium between (auto) adsorption of its own atoms on this facet of Nad and negative charged surface vacancies (NCSV). On this basis, the ASP scale is a scale of adsorption potentials with point defects—the NCSV and adatoms, which determine their surface statistics as a result of the action of surface and electrostatic forces on these quasiparticles. This dualism is aimed at overcoming differences in the understanding of the surface potential in Helmgholz theory and Gibbs theory. The adsorption scale of the singular metal face has a special point—the potential of the zero charge (PZC) of the electrode $$E_{{\text{N}}}^{0}{\text{ = }}-\Delta G_{{\text{S}}}^{0}{{(hkl)} \mathord{\left/ {\vphantom {{(hkl)} {zF}}} \right. \kern-0em} {zF}}$$ with a minimum of adsorption of atoms and NCSV. Point of absolute adsorption devides the scale of cathodic and anodic polarization (Fig. 4.1, Part 1) with predominant adsorption of NCSV or adatoms, reaching the maximum degree at the potential of the second special point $$E_{{\text{S}}}^{0}$$ in each area of the ideal electrode polarization. Part 2 discusses the transition from the ASP to hydrogen scale using the ratio between the standard and absolute values ​​of a hydrogen electrode adopted by the International Union of Physical and Applied Chemistry. Combining the ASP scale with the scale of the absolute potentials of electrode reactions made it possible to calculate the electrode potential of a chemisorption and electrocatalytic reaction of hydrogen evolution on various metals, as well as the potential for the formation of passivating oxide on metals (Ni, Cr), known as the “Flade potential.”

A Scale of Absolute Surface Potentials of Metals. Part I

The problem of the absolute electrode potentials of metals is considered as a problem that encompasses both the thermodynamics of electrode reactions on metals and the surface state of a metal. Within the framework of the physical chemistry of the surface, an adsorption model of the surface layer (SL) of a metal is developed, differing by using the value of the excessive Gibbs surface energy $$\Delta {{G}_{{\text{S}}}}.$$ For the low-index facet (hkl) of the metal, the magnitude of the absolute surface potential is introduced as Es = $${{\Delta {{G}_{{\text{S}}}}} \mathord{\left/ {\vphantom {{\Delta {{G}_{{\text{S}}}}} {zF}}} \right. \kern-0em} {zF}}$$ (z is the valence of metal), which, like the magnitude, depends on the electrode potential. On the other hand, a statistical model is used that relates the autoadsorption of point defects, the surface atomic vacancies V(S) in SL, and adatoms with the surface energy as $$\Delta {{G}_{{\text{S}}}}$$ = –RTlnNV(S)= –RTlnNad. For an uncharged metal, the uncharged metal value $$\Delta G_{{_{{\text{S}}}}}^{0}$$ is maximum, which gives a minimum of the mole fraction of Nad = NV(S) and leads to a zero charge potential formula as $$E_{N}^{0}$$ = – $${{\Delta G_{{\text{S}}}^{0}} \mathord{\left/ {\vphantom {{\Delta G_{{\text{S}}}^{0}} {zF}}} \right. \kern-0em} {zF}}$$ . The ideal polarization of the electrode relative to EN values of $$\Delta G_{{\text{S}}}^{{}}$$ and Gadsto zero that corresponds to the maximum of NV(S) or Nad. These extreme points of the surface activity of atoms determine the scale of absolute values of Es calculated using known table values $$\Delta {{G}_{{\text{S}}}}$$ (hkl) at T = 0 K obtained by the DFT method. When assessing the effect of temperature or potential, the change in the ΔGS and NV(S) (or Nad) values in thermal and electrochemical processes is considered. In Part 2, an application of this scale to the processes of evolution of hydrogen and passivation of metals is considered.

Low-Temperature Detectors for CMB Imaging Arrays

We review advances in low temperature detector (LTD) arrays for Cosmic Microwave Background (CMB) polarization experiments, with a particular emphasis on imaging arrays. We briefly motivate the science case, which has spurred a large number of independent experimental efforts. We describe the challenges associated with CMB polarization measurements and how these challenges impact LTD design. Key aspects of an ideal CMB polarization imaging array are developed and compared to the current state-of-the-art. These aspects include dual-polarization-sensitivity, background-limited detection over a 10:1 bandwidth ratio, and frequency independent angular responses. Although existing technology lacks all of this capability, today's CMB imaging arrays achieve many of these ideals and are highly advanced superconducting integrated circuits. Deployed arrays map the sky with pixels that contain elements for beam formation, polarization diplexing, passband definition in multiple frequency channels, and bolometric sensing. Several detector architectures are presented. We comment on the implementation of both transition-edge-sensor bolometers and microwave kinetic inductance detectors for CMB applications. Lastly, we discuss fabrication capability in the context of next-generation instruments that call for $\sim 10^6$ sensors.

Polarity inversion of aluminum nitride by direct wafer bonding

A novel fabrication process based on direct bonding technologies is proposed and demonstrated to achieve polarity inversion in AlN. High-angle annular dark-field scanning transmission electron microscopy observation clearly showed an atomically flat bonding interface and an abrupt transition from Al polarity (+c) to N polarity (−c) through a single monolayer. This ideal polarity inversion of III–nitride materials is expected to provide new insight into heteropolar device applications.

Improving the lifetime in optical microtraps by using elliptically polarized dipole light

Tightly focused optical dipole traps induce vector light shifts ("fictitious magnetic fields") which complicate their use for single-atom trapping and manipulation. The problem can be mitigated by adding a larger, real magnetic field, but this solution is not always applicable; in particular, it precludes fast switching to a field-free configuration. Here we show that this issue can be addressed elegantly by deliberately adding a small elliptical polarization component to the dipole beam. In our experiments with single $^{87}$Rb atoms in a chopped trap, we observe improvements up to a factor 11 of the trap lifetime compared to the standard, seemingly ideal linear polarization. This effect results from a modification of heating processes via spin-state diffusion in state-dependent trapping potentials. We develop Monte-Carlo simulations of the evolution of the atom's internal and motional states and find that they agree quantitatively with the experimental data. The method is general and can be applied in all experiments where the longitudinal polarization component is non-negligible.

Generalized method for probing ideal initial polarization states in multibeam Lloyd's mirror interference lithography of 2D scale gratings

Delicate control of the initial polarization states of sub-beams incident to the interferometer unit in multibeam Lloyd's mirror interference lithography is of great significance for the fabrication of high-precision two-dimensional (2D) scale gratings. In this work, the optimization of the initial polarization states of incident sub-beams is formulated as a constrained multiobjective optimization problem. A generalized method that allows the incident sub-beams to initially have the general elliptical polarization states in the optimization is proposed based on the multiobjective genetic algorithm. It is demonstrated that the method is capable of delivering ideal initial polarization states with which the cross-interference between the two once-reflected sub-beams on the grating substrate of the interferometer unit can be completely eliminated from the resultant 2D interference fringes. The feasibility of the proposed method is verified through the comparison between the simulated 2D interference fringes and the fabricated 2D scale gratings under the achieved ideal initial polarization states.

An Efficient CSI Feedback Scheme for Dual-Polarized Massive MIMO

As an effective solution to the tradeoff between array size and the number of antenna elements, dual-polarization antenna is widely utilized in massive MIMO systems. However, the existing channel state information (CSI) feedback schemes are not suitable for dual-polarized massive MIMO as they ignore the polarization leakage between the polarization directions, causing significant performance degradation. To facilitate accurate channel acquisition, this paper proposes a practical channel model for dual-polarized massive MIMO by taking polarization leakage into consideration. The model formulates the channel as the sum of two components, i.e., the ideal polarization channel and the polarization leakage channel between the polarization directions. Based on the channel model, the eigenvector structures of both the ideal polarization channel and the polarization leakage channel are analyzed. Moreover, two novel CSI feedback schemes are also designed, i.e., explicit feedback scheme (EFS) and implicit feedback scheme (IFS). In EFS, the parameters determining the eigenvectors of the two channels are fed back explicitly, while the two channels are fed back using predetermined codebook in IFS. Extensive link level and system level simulations are conducted to validate the performance of the proposed schemes and the results show that they significantly outperform the existing CSI feedback schemes.

Comparison of the energy characteristics of tightly focused needle beams with longitudinal polarization

A comparative analysis is made of spatial variations in the energy characteristics of tightly focused, longitudinally polarized needle laser beams generated by an optical system with selective thin-film linear-to-radial polarization conversion, followed by their spatial filtering and tightannular focusing to subwavelength sizes. For the important special case of ideal radial polarization of a focused beam, longitudinal cross-sections of spatial distributions of the electric energy density and the Poynting vector modulus in the vicinity of the focus were compared by numerical simulation. It is shown that the degree of their difference increases substantially with decreasing angular zone of annular focusing and with the introduction of spatial-frequency filtering. It is established that the dimensions of the axial zone of beam focusing determined for their central lobes in the first approximation do not depend on the choice of energy characteristics used for their measurements.

Low-cost encoder using a phase shifting algorithm utilizing polarization properties of light.

In this work a novel polyphase optical encoder is presented, which uses a mathematical algorithm to take advantage of the polarization properties of light. This optical encoder has excellent accuracy, precision, and resolution in measuring the angular position of a shaft. Furthermore, it is designed to work with low-cost optical components. Initially, a light beam passes through a rotating polarizer, and readings are obtained from low-cost photoresistors located under phase shifted analyzers to generate characteristic curves for each of the phases, in the plane formed by the measured angle and the intensity of light. These curves are correlated to the ideal polarization curve formed by Malus' law via polynomial expressions to obtain the relationship between actual values and the ideal square cosine. After this characterization process, the encoder is ready for indefinite use, and operational data are introduced to a phase shifting algorithm, to obtain the angle position of any rotating device.

Wafer-scale monodomain films of spontaneously aligned single-walled carbon nanotubes.

The one-dimensional character of electrons, phonons and excitons in individual single-walled carbon nanotubes leads to extremely anisotropic electronic, thermal and optical properties. However, despite significant efforts to develop ways to produce large-scale architectures of aligned nanotubes, macroscopic manifestations of such properties remain limited. Here, we show that large (>cm(2)) monodomain films of aligned single-walled carbon nanotubes can be prepared using slow vacuum filtration. The produced films are globally aligned within ±1.5° (a nematic order parameter of ∼1) and are highly packed, containing 1 × 10(6) nanotubes in a cross-sectional area of 1 μm(2). The method works for nanotubes synthesized by various methods, and film thickness is controllable from a few nanometres to ∼100 nm. We use the approach to create ideal polarizers in the terahertz frequency range and, by combining the method with recently developed sorting techniques, highly aligned and chirality-enriched nanotube thin-film devices. Semiconductor-enriched devices exhibit polarized light emission and polarization-dependent photocurrent, as well as anisotropic conductivities and transistor action with high on/off ratios.

(Invited) Physics and Applications of Spontaneously Aligned Macroscopic Nanotube Assemblies

One of the outstanding challenges in nanotechnology is how to assemble individual nano-objects into macroscopic architectures while preserving their extraordinary properties. For example, the one-dimensional character of electrons in individual carbon nanotubes leads to extremely anisotropic transport, optical, and magnetic phenomena, but their macroscopic manifestations have been limited. Here, we describe novel methods for preparing macroscopic films, sheets, and fibers of highly aligned carbon nanotubes and their applications to basic and applied studies. Sufficiently thick films act as ideal terahertz polarizers, and appropriately doped films operate as polarization-sensitive, flexible, powerless, and ultrabroadband photodetectors. Together with recently developed chirality enrichment methods, these developments will allow us to probe, understand, and control dynamic conductivities of interacting one-dimensional electrons in macroscopic single crystals of single-chirality single-wall carbon nanotubes.

Anisotropic Properties of Ultra-Thin Freestanding Multi-Walled Carbon Nanotubes Film for Terahertz Polarizer Application

Anisotropic transmission of ultrathin freestanding multi-walled carbon nanotubes (MWCNTs) film has been investigated using terahertz (THz) time-domain spectroscopy. The super-aligned MWCNTs films were fabricated by a novel method—drawing and winding carbon nanotubes on square-shaped polytetrafluoroethylene (PTFE) frame. The MWCNTs film exhibited anisotropic transmittance of THz wave depending on the alignment direction of carbon nanotubes relative to the THz wave polarization orientation, which proved that such MWCNTs film acts as an ideal polarizer in the THz regime. The degree of polarization (DOP) of 99.4% and the extinction ratio (ER) of 25.3 dB (average value) has been demonstrated for a MWCNTs film of 9- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> thickness in a wide frequency range from 0.1 to 2.5 THz. Furthermore, the value of DOP and ER can be engineered expediently by controlling the film thickness. Our approach opens the possibility of MWCNTs film in application of THz optoelectronic devices.

Nonnormal operators in physics, a singular-vectors approach: illustration in polarization optics.

The singular-vectors analysis of a general nonnormal operator defined on a finite-dimensional complex vector space is given in the frame of a pure operatorial ("nonmatrix," "coordinate-free") approach, performed in a Dirac language. The general results are applied in the field of polarization optics, where the nonnormal operators are widespread as operators of various polarization devices. Two nonnormal polarization devices representative for the class of nonnormal and even pathological operators-the standard two-layer elliptical ideal polarizer (singular operator) and the three-layer ambidextrous ideal polarizer (singular and defective operator)-are analyzed in detail. It is pointed out that the unitary polar component of the operator exists and preserves, in such pathological case too, its role of converting the input singular basis of the operator in its output singular basis. It is shown that for any nonnormal ideal polarizer a complementary one exists, so that the tandem of their operators uniquely determines their (common) unitary polar component.

Extreme-sensitivity terahertz polarizer inspired by an anisotropic cut-through metamaterial.

Submilliradian accuracy utilizing terahertz waves is used to often discover and observe novel physical phenomena. However, conventional terahertz polarizers cannot simultaneously realize a high extinction ratio, which restricts the sensitivity of the polarization angle, and a high transmission power across a broad frequency band due to the wires involved. Here, inspired by metamaterials, we demonstrate an anisotropic cut-through metal-slit array for an ideal terahertz polarizer with a high extinction ratio and transmission power. Measurements confirm extinction ratios below approximately -50 dB and average transverse magnetic-mode transmission powers of over 80% from 0.3 to 2.2 THz. The extremely sensitive mechanism can shed light on a variety of path-breaking applications such as single-photon detection and quantum information and communication at lower frequencies.

Coherent optical control of polarization with a critical metasurface

We describe the mechanism by which a metamaterial surface can act as an ideal phase-controlled rotatable linear polarizer. With equal-power linearly polarized beams incident on each side of the surface, varying the relative phase rotates the polarization angles of the output beams, while keeping the polarization exactly linear. The explanation is based on coupled-mode theory and the idea of coherent perfect absorption into auxiliary polarization channels. The polarization-rotating behavior occurs at a critical point of the coupled-mode theory, which can be associated with the exceptional point of a parity-time (PT) symmetric effective Hamiltonian.

Electrochemical Characterization of 1 Wt% Mixture of 1-Ethyl-3-Methylimidazolium Chloride and 1-Ethyl-3-Methylimidazolium Tetrafluoroborate|Bi(111) Interface

As the global energy need is in a constant growth new and more effective ways of energy production and storage have to be developed. Electrical double-layer capacitors (EDLC) are widely discussed and some even used as energy storage devices due to their high power densities and good cycling stability. However, as a drawback they often suffer from limited energy densities which for example could be improved by developing and applying new electrolytes with broader region of application potentials (ΔE) in comparison with aqueous electrolytes1-3. Different room temperature ionic liquids (RTIL) could be theoretically used as a good alternatives possessing besides possibly higher ΔE also lower vapor pressure or higher thermal stability3. Therefore, the purpose of this work was to determine the electrochemical characteristics of the 1 wt% mixture of 1-ethyl-3-methylimidazolium tetrafluoroborate and 1-ethyl-3-methyl-imidazolium chloride as one of the newest potential electrolytes for EDLCs using Bi(111) as an electrode with well reproducible characteristics. The measurements were carried out in a three electrode system using electrochemically polished Bi(111) as a working electrode, Ag wire coated with AgCl as a reference electrode and Pt net as a counter electrode. The mixture was prepared by dissolving 1 wt% EMImCl (Merck KGaA, ≥ 98.0 %) in EMImBF4 (Fluka Analytical, ≥ 99.0 %) and then heating it up to 80 . The Bi(111)|EMImBF4 and EMImCl interface was studied using electrochemical impedance spectroscopy and cyclic voltammetry. Current density (j) vs. electrode potential (E) dependencies obtained showed that the region of ideal polarization for EMImBF4 containing 1 wt% of EMImCl was from -1.0 V to -0.3 V, whereas for the mixture of EMImBF4 and EMImI (the same concentration) it was from -1.0 V to -0.2 V (vs. Ag|AgCl)4. The experimental differential capacitance, potential (C vs. E) curves measured at constant ac frequency (210 Hz) were acquired using electrochemical impedance spectroscopy. The reversible nature of the system was determined by measuring first towards more positive potential directions and then towards more negative potential values. Comparison of data for EMImBF4 + EMImCl and EMImBF4 + EMImI4 mixtures (1 wt%) showed that the capacitance values of the former were noticeably lower than that of I- containing RTIL mixture. Clear dependance of adsorption characteristics on frequency and potential applied can be seen on Nyquist and phase angle (δ) vs. frequency (f) plots. The nearly ideal capacitive behavior of the system appeared in a narrow region of frequencies in the part of intermediate f values (2-100 Hz) and showed only light diminishing at lower f values (0.1-2 Hz). The series differential capacitance (Cs ) values were calculated from Nyquist plots (, where ) at different fixed frequencies. Obtained Cs vs. E plots indicated that at more positive potentials, where the specific adsorption of Cl- ions takes place, the Cs values increase with the decrease of frequency applied. References M. Kim, I. Oh, J. Kim, J. Mater. Chem. A 3, 3944 (2015)K. Fic, G. Lota, M. Meller, E. Frackowiak, Energy Environ. Sci. 5, 5842 (2012)N. D. Khupse, A. Kumar Indian J. Chem. 49A, 635 (2010)C. Siimenson, L. Siinor, K. Lust, E. Lust, J. Electroanal. Chem. 730, 59 (2014) Acknowledgments This study was partially funded by the Estonian Energy Technology Program project SLOKT10209T, IUT20-13 and Estonian Centers of Excellence in Science project: High-technology Materials for Sustainable Development TK117 and PUT55.

Stochastic Path Model of Polaroid Polarizer for Bell's Theorem and Triphoton Experiments

Depending on the outcome of the triphoton experiment now underway, it is possible that the new local realistic Markov Random Field (MRF) models will be the only models now available to correctly predict both that experiment and Bell's theorem experiments. The MRF models represent the experiments as graphs of discrete events over space-time. This paper extends the MRF approach to continuous time, by defining a new class of realistic model, the stochastic path model, and showing how it can be applied to ideal polaroid type polarizers in such experiments. The final section discusses possibilities for future research, ranging from uses in other experiments or novel quantum communication systems, to extensions involving stochastic paths in the space of functions over continuous space. As part of this, it derives a new Boltzmann-like density operator over Fock space, which predicts the emergent statistical equilibria of nonlinear Hamiltonian field theories, based on our previous work of extending the Glauber–Sudarshan P mapping from the case of classical systems described by a complex state variable α to the case of classical continuous fields. This extension may explain the stochastic aspects of quantum theory as the emergent outcome of nonlinear PDE in a time-symmetric universe.

Sum decomposition of Mueller-matrix images and spectra of beetle cuticles.

Spectral Mueller matrices measured at multiple angles of incidence as well as Mueller matrix images are recorded on the exoskeletons (cuticles) of the scarab beetles Cetonia aurata and Chrysina argenteola. Cetonia aurata is green whereas Chrysina argenteola is gold-colored. When illuminated with natural (unpolarized) light, both species reflect left-handed and near-circularly polarized light originating from helicoidal structures in their cuticles. These structures are referred to as circular Bragg reflectors. For both species the Mueller matrices are found to be nondiagonal depolarizers. The matrices are Cloude decomposed to a sum of non-depolarizing matrices and it is found that the cuticle optical response, in a first approximation can be described as a sum of Mueller matrices from an ideal mirror and an ideal circular polarizer with relative weights determined by the eigenvalues of the covariance matrices of the measured Mueller matrices. The spectral and image decompositions are consistent with each other. A regression-based decomposition of the spectral and image Mueller matrices is also presented whereby the basic optical components are assumed to be a mirror and a circular polarizer as suggested by the Cloude decomposition. The advantage with a regression decomposition compared to a Cloude decomposition is its better stability as the matrices in the decomposition are determined a priori. The origin of the depolarizing features are discussed but from present data it is not possible to conclude whether the two major components, the mirror and the circular polarizer are laterally separated in domains in the cuticle or if the depolarization originates from the intrinsic properties of the helicoidal structure.

Photonic spin Hall effect in hyperbolic metamaterials for polarization-controlled routing of subwavelength modes

The routing of light in a deep subwavelength regime enables a variety of important applications in photonics, quantum information technologies, imaging and biosensing. Here we describe and experimentally demonstrate the selective excitation of spatially confined, subwavelength electromagnetic modes in anisotropic metamaterials with hyperbolic dispersion. A localized, circularly polarized emitter placed at the boundary of a hyperbolic metamaterial is shown to excite extraordinary waves propagating in a prescribed direction controlled by the polarization handedness. Thus, a metamaterial slab acts as an extremely broadband, nearly ideal polarization beam splitter for circularly polarized light. We perform a proof of concept experiment with a uniaxial hyperbolic metamaterial at radio-frequencies revealing the directional routing effect and strong subwavelength λ/300 confinement. The proposed concept of metamaterial-based subwavelength interconnection and polarization-controlled signal routing is based on the photonic spin Hall effect and may serve as an ultimate platform for either conventional or quantum electromagnetic signal processing.