Optical Rotatory Power Research Articles

Optical Activities of Organic Crystals: Crystal Orbital Formulation of Anisotropic Gyration.

To describe the optical activities of crystals, gyration tensors are necessary for all wavelengths of incident light. To date, few studies on direct calculations of gyration tensors from Bloch states have been conducted. Herein, a practical procedure to obtain gyration tensors of organic crystals is presented using the crystal orbital method. The extended Hückel method was adopted to evaluate the gyration tensors, epitomizing the one-electron formulation. To confirm the validity of the formulation, the optical rotatory power of alanine and γ-glycine was examined. The reproduced profiles of the optical rotatory power were consistent with the results of recent experiments. This is a general formulation of the one-electron theory of optical activities for three-dimensional crystals. In principle, the optical rotatory strength tensor is not invariant with translation. For systems with small unit cells, however, the formalism is quasi-invariant with respect to translation. The quasi origin-independent formalism is sufficiently substantial to be applicable to modern crystal optics.

Standard Response Calculation of Electric Dipole Polarizability and Specific Optical Rotation Power Densities.

A time-dependent method has been developed to solve the standard response equation for the calculation of dynamic molecular property densities, endowed with the characteristic of being origin-invariant, entirely in the atomic orbital basis at both HF and DFT level of theory. The method has been tuned in particular for the calculation of origin-independent electric dipole polarizability density and specific rotation power density. Some demonstrations are given for the hexabenzocoronene molecule and the Tröger's base.

Quantum optomagnetics in graphene

Graphene can be magnetized through nonlinear response of its orbital angular momentum to an intense circularly polarized light. This optomagnetic effect can be well exemplified by the inverse Faraday effect (IFE) where an optically-generated DC magnetization leads to graphene’s optical activity. We provide a single-particle quantum mechanical model of an IFE in graphene by solving Schrödinger’s equation in the presence of a renormalized Hamiltonian near a Dirac point in the presence of circularly polarized monochromatic light. We derive an analytical expression for DC magnetization based on non-perturbative and dressed states of quasi-electrons where their energy spectrum is isotropically gapped by the circularly polarized light. Optical rotatory power is then computed through the gyroelectric birefringence where a measurable polarization rotation angle under moderate and intense optical radiations is predicted.

First-principles calculation of the optical rotatory power of periodic systems: Modern theory with modern functionals

First-principles calculation of the optical rotatory power of periodic systems: Modern theory with modern functionals

Quartz‐Like Structure, Optical Activity, and High Stability in the First Chiral Cation‐Coordinated Perovskite Semiconductor

AbstractPoor stability is a significant challenge to organic–inorganic hybrid perovskites for practical optoelectronic applications, which results from their inherent ionic nature and soft structures. The coordination bonding strategy is supposed to be a valid approach by enhancing the interaction between the cations and inorganic frameworks. Herein, the first pair of cation‐coordinated perovskites with high stability, achieved through coordination bonds between the cations and [PbXn] anions instead of the weak hydrogen bonds and van der Waals force presented in conventional ionic perovskites, is reported. In L/R‐(4HOPD)PbBr3 (4HOPD = 4‐hydroxypiperidine cation) (L/R=Left/Right–handed), one of the six halogen atoms is replaced by an oxygen atom from the cation. The PbO bond contributes to the high stability under a double 85 test. L/R‐(4HOPD)PbBr3 crystallizes in the tetragonal system, belonging to one of 11 enantiomorphic space group types, P41212 and P43212. Similar to quartz, the chirality originates from the helical assembly of achiral units. The chirality‐induced optical rotatory power is 16.84° mm−1 at 404 nm. Moreover, the uniaxial negative birefringent property with a comparable Δn value makes it a good alternative to quartz. The remarkable stability of this new perovskite presents significant potential for further investigation into stable perovskites and their applications in optical rotation and polarizing optics.

Mechanism of Photoinduced Gyrotropic Phenomena in Amorphous As2S3

Little is known why illumination of linearly polarized continuous‐wave laser light can induce gyrotropy (optical rotatory power) and macroscopic circular/screwing deformations in amorphous As2S3. Gyrotropy appears through scattering and deflection of the incident light in combination with negative photoinduced birefringence. The gyrotropy could also trigger atomic motions under photoinduced fluidity, which produces macroscopic deformations.

Optical rotation in the lithium triborate nonlinear crystal

A dual-wavelength polarimetric technique at 633 and 661 nm has been used for the characterization of a nonlinear lithium triborate (LiB3O5) nonenantiomorphous biaxial crystal. The mismatch of the crystallographic and optical coordinate systems was taken into account. The optical rotatory power for light propagation along one of the optical axes is ρ = 7.06° mm−1. The gyration tensor component along the bisector between the x and y crystallographic axes has been measured as g 12 = 4.31 × 10−5. Computed values based on the crystalline structure and electronic polarizabilities are in good agreement with those obtained experimentally.

Electronic current densities and origin-independent property densities induced by optical fields.

The interaction of a molecule with optical fields is customarily interpreted by means of induced time-dependent electric polarizabilities, magnetizabilities and mixed electric-magnetic polarizabilities. In general, these properties can be rationalized by integrals of density functions formulated in terms of induced charge and current densities. In this perspective, we focus on what has been done so far at the theoretical level, and on what can be expected to be unveiled from the topological study of suitable density functions, endowed with the fundamental requirement of origin invariance. Densities characterized by such a property can be integrated all over the configuration space to obtain electric dipole polarizability and optical rotatory power. Corresponding maps visualize domains mainly involved in the molecular response. The diagonal components of origin-independent density tensor functions that, on integration, yield corresponding electric dipole polarizability tensor of benzene, naphthalene, phenanthrene and ovalene, have been computed, confirming the ubiquitous presence of counter-polarization regions in the proximity of the atomic nuclei. They are associated with toroidal electron currents, induced by time derivative of the electric field of impinging radiation. Electron (de)localization in these systems is readily observed and estimated. The optical rotation density of the carbonyl chromophore is studied in detail. Its essential feature is the separation in quadrants of alternating sign of density about the CO bond. The presence of an extrachromophoric perturbation determines asymmetry in the extension of the quadrant distribution, thus causing optical rotation.

3D Laser Displays Based on Circularly Polarized Lasing from Cholesteric Liquid Crystal Arrays.

3D laser displays play an important role in next-generation display technologies owing to the ultimate visual experience they provide. Circularly polarized (CP) laser emissions, featuring optical rotatory power and invariability under rotations, are attractive for 3D displays due to potential in enhancing contrast ratio and comfortability. However, the lack of pixelated self-emissive CP microlaser arrays as display panels hinders the implementation of 3D laser displays. Here, full-color 3D laser displays are demonstrated based on CP lasing with inkjet-printed cholesteric liquid crystal (CLC) arrays as display panels. Individual CP lasers are realized by embedding fluorescent dyes into CLCs with their left-/right-handed helical superstructures serving as distributed feedback microcavities, bringing in ultrahigh circular polarization degree values (gem = 1.6). These CP microlaser pixels exhibit excellent far-field color-rendering features and a relatively large color gamut for high-fidelity displays. With these printed CLC red-green-blue (RGB) microlaser arrays serving as display panels, proof-of-concept full-color 3D laser displays are demonstrated via delivering images with orthogonal CP laser emissions into one's left and right eyes. These results provide valuable enlightenment for the development of 3D laser displays.

Electronic Currents Induced by Optical Fields and Rotatory Power Density in Chiral Molecules.

The electric dipole–magnetic dipole polarizability tensor , introduced to interpret the optical activity of chiral molecules, has been expressed in terms of a series of density functions , which can be integrated all over the three-dimensional space to evaluate components and trace . A computational approach to , based on frequency-dependent electronic current densities induced by monochromatic light shining on a probe molecule, has been developed. The dependence of on the origin of the coordinate system has been investigated in connection with the corresponding change of . It is shown that only the trace of the density function defined via dynamic current density evaluated using the continuous translation of the origin of the coordinate system is invariant of the origin. Accordingly, this function is recommended as a tool that is quite useful for determining the molecular domains that determine optical activity to a major extent. A series of computations on the hydrogen peroxide molecule, for a number of different HO–OH dihedral angles, is shown to provide a pictorial documentation of the proposed method.

First-Principles Calculation of the Optical Rotatory Power of Periodic Systems: Application on α-Quartz, Tartaric Acid Crystal, and Chiral (n,m)-Carbon Nanotubes.

The self-consistent coupled-perturbed (SC-CP) method in the CRYSTAL program has been adapted to obtain electromagnetic optical rotation properties of chiral periodic systems based on the calculation of the magnetic moment induced by the electric field. Toward that end, an expression for the magnetic transition moment is developed, which involves an appropriate electronic angular momentum operator. This operator is forced to be hermitian so that the chiroptical properties are real. In our formulation, the trace of the optical rotatory power matrix is gauge-origin-invariant as long as the electric dipole transition matrix elements are obtained using the velocity (rather than position) operator. On the other hand, the component along the optic axis is invariant in general for uniaxial and biaxial crystals. Under the same conditions, these properties also do not depend on the so-called missing integers that occur in the treatment of the electric dipole moment of quasi-one-dimensional periodic systems or the analogue of missing integers for the case of higher dimensionality. Tests on a model H2O2 polymer confirm the formalism and, as desired, show that the calculated properties are independent of the size and definition of the unit cell. In addition, an empirical relation to a finite oligomer gauge-including atomic orbital (GIAO) calculation is found. Applications, with comparison to experiment, are carried for α-quartz, tartaric acid crystal, and carbon nanotubes. Future developments of this initial approach to chiroptical properties in the solid state are noted.

Enhancing the optical rotation of chiral molecules using helicity preserving all-dielectric metasurfaces

Being able to sense and distinguish the handedness of chiral molecules is crucial for many applications in the life sciences. Here, we explore by theoretical and computational means the ability of achiral and helicity preserving photonic nanostructures to enhance the optical rotation, i.e., the polarization rotation of elliptically polarized light while traversing a solution of chiral molecules. Starting from a helicity preserving isolated dielectric cylinder, we assemble an array thereof, which enhances the optical rotation power by a factor of four, being limited by the inability to enhance the helicity density beyond the near fields attached to the array. To overcome this limitation, we study cavities composed of two arrays of cylinders with the solution of molecules in between. Such cavities enhance the optical rotation power by a factor as large as 270. Our work complements previous research that concentrated on enhancing circular dichroism with similar structures. Measuring and enhancing circular dichroism as well as optical rotation provides more complete information about the molecules under investigation.

Optical vector field rotation and switching with near-unity transmission by fully developed chiral photonic crystals

State-of-the-art nanostructured chiral photonic crystals (CPCs), metamaterials, and metasurfaces have shown giant optical rotatory power but are generally passive and beset with large optical losses and with inadequate performance due to limited size/interaction length and narrow operation bandwidth. In this work, we demonstrate by detailed theoretical modeling and experiments that a fully developed CPC, one for which the number of unit cells N is high enough that it acquires the full potentials of an ideal (N → ∞) crystal, will overcome the aforementioned limitations, leading to a new generation of versatile high-performance polarization manipulation optics. Such high-N CPCs are realized by field-assisted self-assembly of cholesteric liquid crystals to unprecedented thicknesses not possible with any other means. Characterization studies show that high-N CPCs exhibit broad transmission maxima accompanied by giant rotatory power, thereby enabling large (>π) polarization rotation with near-unity transmission over a large operation bandwidth. Polarization rotation is demonstrated to be independent of input polarization orientation and applies equally well on continuous-wave or ultrafast (picosecond to femtosecond) pulsed lasers of simple or complex (radial, azimuthal) vector fields. Liquid crystal-based CPCs also allow very wide tuning of the operation spectral range and dynamic polarization switching and control possibilities by virtue of several stimuli-induced index or birefringence changing mechanisms.

Net atomic charges, electric moments, and sign and magnitude of optical rotatory power in α-TeO2 at 296 K

Optical activity is determined from a point charge model in one enantiomorph of a chiral and semiconducting α-TeO2 crystal. Net atomic charges of Te and O atoms are iterated and electric moments derived. Second electric moments in the principal axis directions are calculated and their ratio is fitted by comparison with the corresponding ratio of the optical refraction indices. The components of the axial vectors are calculated and converted to the gyration tensor components. The optical rotatory power in the positive direction of the optic axis is determined, and the sense of optical rotation is defined from transformations of polar vectors of first rank of the TeO2 groups and visually confirmed in both enantiomorphs.

Dynamic chiral magnetic effect and anisotropic natural optical activity of tilted Weyl semimetals

We study the dynamic chiral magnetic conductivity (DCMC) and natural optical activity in an inversion-broken tilted Weyl semimetal (WSM). Starting from the Kubo formula, we derive the analytical expressions for the DCMC for two different directions of the incident electromagnetic wave. We show that the angle of rotation of the plane of polarization of the transmitted wave exhibits remarkable anisotropy and is larger along the tilt direction. This striking anisotropy of DCMC results in anisotropic optical activity and rotary power, which can be experimentally observed as a topological magneto-electric effect of inversion-broken tilted WSMs. Finally, using the low energy Hamiltonian, we show that the DCMC follows the universal frac{{bf{1}}}{{{boldsymbol{omega }}}^{{bf{2}}}} decay in the high frequency regime. In the low frequency regime, however, the DCMC shows sharp peaks at the tilt dependent effective chemical potentials of the left-handed and right-handed Weyl points. This can serve as a signature to distinguish between the type-I and type-II Weyl semimetals.

A General Recipe for Nondispersive Optical Activity in Bilayer Chiral Metamaterials

AbstractBy mimicking broken mirror symmetry of naturally existing chiral materials, and exploiting even stronger magnetoelectric coupling, large optical activity has been realized in chiral metamaterials over the past decade. Nevertheless, most of chiral metamaterials demonstrated so far exhibit highly dispersive optical activity due to their resonant response, which inevitably leads to a narrow operating bandwidth in terms of the optical rotatory power as well as the transmission. Herein, conditions for possessing nondispersive optical activity are derived based on a Lagrangian model for general bilayer chiral metamaterials, and the validity is experimentally confirmed in a microwave regime. It is shown that large nondispersive optical activity can be realized in bilayer chiral metamaterials where metallic apertures are arranged in each layer with high‐rotational symmetry and the off‐diagonal terms of the magnetic interlayer coupling tensor are nonzero while the electric counterparts are eliminated. In stark contrast to most previous chiral metamaterials, a nonzero constant polarization rotation angle is observed at the quasi‐static limit, which manifests the unique nonresonant characteristic of the proposed magnetically coupled bilayer chiral metamaterials. In addition to the geometrical controllability, the amount of polarization rotation and transmission bandwidth can be further increased by stacking magnetically coupled bilayer chiral metamaterials.

Optical rotatory power of quartz between 77 K and 325 K for 1030 nm wavelength

We report on the experimental characterisation of the temperature dependence of the optical rotatory power of crystalline right-handed $\alpha$α-quartz at 1030 nm wavelength. The temperature range covered in this study is between 77 K and 325 K. For the measurement we propagated light through a 13.11 mm thick quartz plate collinearly with the optic axis. The plate is anti-reflection coated and rotates the polarisation plane of 1030 nm light by 89.3 deg at room temperature, corresponding to a specific rotatory power of 6.8 deg/mm. When placed between parallel polarisers, the transmission through the system was 0.03% at room temperature and increased to 1% at 77 K, showing a measurable change in rotatory power. At 77 K, the angle of rotation imparted by the quartz plate is 85 deg, corresponding to a specific rotatory power of 6.5 deg/mm. To the best of our knowledge, this is the first time that the temperature dependence of optical activity of $\alpha$α-quartz is reported for cryogenic temperatures in the infrared. We expect that the measurement results provided in this paper will assist in the design and characterisation of optical systems operating under cryogenic conditions.

Optical polarization states of a liquid-crystal blue phase II

The advantages and uniqueness of blue-phase-based electro-optical devices are predicted. In this paper, we present relevant electro-optics behaviors of the transmitted and reflected lights of BPII and try to explain those phenomena through studying the polarization states of the lights. There are two stages of electro-optical behaviors seen in an in-plan-switching BPII cell. Because of the Kerr effect, the birefringence of the linear polarized light is induced and saturated 0.021 at 150 V, and the Kerr constant is $\approx 3 \times 10^{-10}\; {\textrm{mV}}^{-2}$≈3×10−10mV−2. As the applied voltage is stronger (>200 V), the influence of the deformation of the lattice structure dominates the transmitted/reflected intensity at different wavelengths, which causes a discontinuous change in the transmitted light intensity and a huge variation in the azimuth angle ($80^{\circ }$80∘) of the polarization state of the transmitted light. As a result the deformation of the lattice structure of the BPII not only induces a linear birefringence but also induces a change in optical rotatory power and then affects the polarization state of the light. These experimental results show that the electro-optical nature of the BPII cell is more complicated than the well-known BPI phase. They also show that BPII can be used not only in transflective devices, but also in field-tunable optical devices.

COLORIMETRIC PROPERTY OF GUEST-HOST LIQUID CRYSTAL DISPLAYS

A bright reflective LCD without a backlight is a key device for portable information systems. The guest-host LCDs use the absorption anisotropy effect of dichroic dyes and have a wide viewing angle cone. The GH-LCD does not need complicated designs of optical compensation in birefringence or optical rotatory power modes. One of the applications of GH-LCDs is a black and white display which works as a light shutter of a full color reflective display with micro-color filters. It is necessary to mix dyes for an achromatic display. The Newton-Raphson method is useful for the calculation of optimum dye concentrations in order to display the designed color. In this work, the judgement of the calculated results is discussed. As a result, the calculated result with Newton-Raphson method is quickly and easily evaluated. The process gives us a helpful guideline in the fabrication of the reflective color LCDs and it is expected that the precise color matching improves the quality of LCDs.

Dual-wavelength polarimeter application in investigations of the optical activity of a langasite crystal.

A method of high-accuracy polarimetry, which includes optical activity measurements' systematic errors, was realized with a dual-wavelength polarimeter for the two wavelengths of 635 and 650 nm. Simultaneous measurements with neighboring wavelengths significantly improved the data processing by increasing the amount of obtained data to eliminate the systematic errors. For a langasite crystal, La3Ga5SiO14, we measured the temperature dependence of the gyration tensor component g11. Our acquired value does not exceed 0.47×10-5 and is much smaller than the previous results obtained by different experimental methods. The results presented in this paper are consistent with the calculated optical rotatory power from the crystal structure data and the polarizabilities of the atoms.