The
influence of the annealing conditions on the thermally stimulated
photoinduced molecular reorientation of a photoinactive liquid crystalline
polymethacrylate with phenyl aldehyde and benzoic acid side groups
(P1) doped with 4-methoxyaniline, which forms photoalignable
4-methoxy-N-benzylideneaniline (MNBA) side groups in situ, was investigated. Light exposure and subsequent
thermal stimulation under a N2 atmosphere realized sufficient
cooperative molecular reorientation (D > 0.7),
but
the simultaneous thermal hydrolysis of the MNBA groups under humid
air lowered the molecular reorientation performance. By contrast,
subsequent thermal hydrolysis of MNBA after molecular reorientation
introduced different aromatic amines into the reoriented P1 film, which regulated the birefringence and photofunctionality of
the oriented film.
Abstract:A vector vortex coronagraph (VVC) is one of promising means for imaging extremely faint objects around bright stars such as exoplanets. We present a design of an achromatic VVC, in which an axially-symmetric half-wave plate (AHP) is placed between crossed polarization filters (circular polarizer and analyzer). The circular polarizer and the analyzer are both composed of a polarizer and a quarter-wave plate (QWP). We demonstrate, via Jones calculus and Fourier analysis, that the achromatic stellar elimination can theoretically be realized by optimal polarization filters, even when chromatic AHP and QWPs are used. We carried out laboratory demonstrations of the designed VVC using a photonic-crystal AHP. As a result, we observed achromatic coronagraphic performance, a light suppression level of 7 × 10 −5 , over a wavelength from 543 nm to 633 nm.
To overcome a trade-off issue between stability and flexibility in generation of ring-shaped optical lattices, we proposed and demonstrated a novel generation method by using axially-symmetric polarization elements. While two optical vortices were coaxially generated, electrically-controlled phase difference between them by an electro-optic modulator enabled a precise rotation of the lattice. Our method has a capability to fulfill both the high-stability and the rapid-rotation. c
The Vector Vortex Coronagraph (VVC) is one of the most attractive new-generation coronagraphs for ground-and space-based exoplanet imaging/characterization instruments, as recently demonstrated on sky at Palomar and in the laboratory at JPL, and Hokkaido University. Manufacturing technologies for devices covering wavelength ranges from the optical to the mid-infrared, have been maturing quickly. We will review the current status of technology developments supported by NASA in the USA (Jet Propulsion Laboratory-California Institute of Technology, University of Arizona, JDSU and BEAMCo), Europe (University of Liège, Observatoire de ParisMeudon, University of Uppsala) and Japan (Hokkaido University, and Photonics Lattice Inc.), using liquid crystal polymers, subwavelength gratings, and photonics crystals, respectively. We will then browse concrete perspectives for the use of the VVC on upcoming ground-based facilities with or without (extreme) adaptive optics, extremely large ground-based telescopes, and space-based internal coronagraphs.
An in situ exchange of oriented mesogenic side groups containing Schiff base moieties realized birefringence control of photoalignable liquid crystalline polymers between 0.13 and 0.44. Both thermal hydrolysis of the oriented side groups and in situ condensation using phenyl amine derivatives with a high inherent birefringence vary the birefringence and thermal stability of oriented films without distortion of the oriented structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.