Chiral structure based on bilayered displaced U pair

A novel chiral nano structure for optical activities and negative refractive index

Aiming to explore birefringence-free tunable terahertz chiral metamaterial structure, a new design without sacrificing cell arrangement compactness is proposed. In the current case, a planar metallic spiral structure demonstrating four-fold (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) rotational symmetry is used. Upon pneumatic actuation induced deformation, it will be translated into a conical quadrifilar helix with a controllable shape. As a result of which, tuning capability over the optical activity and circular dichroism has been successfully achieved from simulation results. Most importantly, besides enantiomeric symmetry, this tuning will not be affected by the in-plane rotation of the linearly polarized incident, demonstrating exciting birefringence-free characteristic.

In this article, recent progress and development of terahertz chiral metamaterials including stereometamaterials are thoroughly reviewed. This review mainly focuses on the fundamental principles of design and arrangement of meta-atoms in metamaterials exhibiting chirality with various asymmetry and symmetry and 2D and 3D configuration. Related optical and propagation properties in chiral metamaterials, such as optical activity, circular dichroism, and negative refraction for each different chiral metamaterials, are compared and investigated. Finally, comparison between chiral metamaterials with stereometamaterials in terms of the polarization selective operation along with the similarity and the distinction is addressed as well.

Transmission characteristics of a helically twisted photonic crystal fiber (PCF) are theoretically investigated by a recently developed beam propagation method for a helicoidal system. Experimentally reported features of the twisted PCF, such as periodical transmission dips, optical activity discontinuity, and circular dichroism, are successfully reproduced in a simulation. We reveal unique properties related to circular dichroism and optical activity in the twisted PCF. Through Stokes parameter evaluation, the polarization state of the input light in the twisted PCF is investigated in detail and the transition from linearly polarized that to circularly polarized light is demonstrated. Furthermore, the optical activity discontinuity is confirmed near the transmission dip.

Terahertz angle-insensitive 90° polarization rotator using chiral metamaterial

Transmission characteristics of helically twisted photonic crystal fiber is theoretically investigated by using recently developed beam propagation method for helicoidal system. Experimentally reported features of twisted PCF, such as periodical transmission dips, optical activity discontinuity, and circular dichroism are successfully reproduced in the simulation.

A complementary Y-shaped chiral metamaterial (CYCMM) is proposed for the realization of giant optical activity and circular polarization with strong circular dichroism (CD) simultaneously for terahertz (THz) waves. It is demonstrated that the proposed CYCMM can achieve 90° linear polarization rotation around 2.13 THz and a giant CD effect at 2.38 THz through full-wave simulations. The mechanism of the giant CD effect and optical activity is illustrated by simulated surface current distribution. Due to strong optical activity and the CD effect, the proposed CYCMM is useful for the development of integrated terahertz spectroscopic and imaging devices.

Optical activity, a foundational part of chemistry, is not restricted to chiral molecules although generations have been instructed otherwise. A more inclusive view of optical activity is valuable because it clarifies structure-property relationships however, this view only comes into focus in measurements of oriented molecules, commonly found in crystals. Unfortunately, measurements of optical rotatory dispersion or circular dichroism in anisotropic single crystals have challenged scientists for more than two centuries. New polarimetric methods for unpacking the optical activity of crystals in general directions are still needed. Such methods are reviewed as well as some of the 'nourishment' they provide, thereby inviting to new researchers. Methods for fitting intensity measurements in terms of the constitutive tensor that manifests as the differential refraction and absorption of circularly polarized light, are described, and examples are illustrated. Single oriented molecules, as opposed to single oriented crystals, can be treated computationally. Structure-property correlations for such achiral molecules with comparatively simple electronic structures are considered as a heuristic foundation for the response of crystals that may be subject to measurement.

Optical rotatory dispersion and circular dichroism properties of yeast mitochondrial DNA's

During the past decade there has been a considerable resurgence of interest in the optical rotatory dispersion and circular dichroism of coordination compounds.1 In addition, there also has been a considerable renewal of interest in the Pfeiffer effect during this same period of time.2-8 This coincidental renewal of interest in these fields is most fortunate, because it is possible to apply optical rotatory dispersion and circular dichroism techniques to the study of the Pfeiffer effect with fruitful results (vide infra).

An analysis of optical rotatory dispersion and circular dichroism of RNA is described which leads to an estimate of the degree of base pairing. By the use of new standards for the double‐helical parts of the molecule, based on data for two‐stranded viral RNA species, a good fit between calculated and observed curves can be achieved. Where data are available the results of analyses of optical rotatory dispersion and circular dichroism in general show satisfactory consistency.

Optical effects are observed in regularly dyed crystals that serve to mimic optical rotation and circular dichroism by rotating the azimuth and increasing the ellipticity of linearly polarized light traversing the samples. However, these effects to which we give the names optical rotatory scattering and circular dichroic scattering do not transform upon rotation of the sample like intrinsic optical rotation and intrinsic circular dichroism. We ascribe this behavior to new scattering consequences that arise here in crystals of K2SO4 containing oriented azo dyes that have been arranged and overgrown in particular growth sectors. Requisite for the apparent optical rotation and circular dichroism is a bias in the inclination of the induced dipoles with respect to the principal light propagation modes of the medium. This unique situation is a consequence of the anisotropy of growth that is unlikely to occur in other dye-doped systems such as polymers or liquid crystals.

Surveys of many of the techniques in nucleic acid chemistry are found in some recent review articles (1–6). A new book by Haschemeyer and Haschemeyer (7) is an excellent text for nearly all the biophysical techniques. In this chapter, we deal briefly with four techniques that have found rather widespread use in recent years: 1. Optical activity [optical rotatory dispersion (ORD) and circular dichroism (CD)] 2. Nuclear magnetic resonance (NMR) 3. Ultracentrifugation 4. Fiber X-ray diffraction

THE optical activity generated by the interaction of small ligands with proteins, visible as extrinsic optical rotatory dispersion (ORD) Cotton effects or circular dichroism (CD) bands, has been used extensively to study the binding of ligands to non-antibody proteins1,2. We describe here the use of circular dichroism to monitor the binding of DNP-lysine to a mouse IgA myeloma protein with high affinity for dinitrophenylated haptens3–5.

The Molecular Basis of Optical Activity: Optical Rotatory Dispersion and Circular Dichroism. By E. Charney. Pp.376. (Wiley: New york and chichester, UK, 1979.) £18.30, $39.90.