2 research outputs found
Full Polarization Control of Optical Planar Waveguides with Chiral Material
Circularly
polarized (CP) light is attracting growing interest in photonics,
however it is not possible to use regular planar waveguides for the
transmission of such CP light. While keeping the planar geometry,
we conceived devices where the chirality of the propagation medium
overcomes the planar symmetry. Thus, we report on the fabrication
of chirowaveguides arising from the stacking of three layers of a
new hybrid chiral organic modified silica (OrMoSil). A flexible strategy
allows the control of the two main parameters impacting the ellipticity
of the propagated waves. First, the high chirality of the transparent
material is based on cheap and easy to access binaphthyl precursors
simply shaped as films by dip-coating. Second, the refractive index
(RI) contrast between the layers is finely tuned by TriEthOxySilane
(TEOS) doping. The polarization of the two fundamental guided modes
is measured on 2 cm long waveguides. We demonstrated that the polarization
can be modulated from linear to nearly circular (80% ellipticity)
depending on the RI contrast and the core thickness. These unprecedented
achievements in the area of both optical materials and guided optics,
open the way to fully integrated photonic devices dealing with CP
light propagation
Au<sub>10</sub>(SG)<sub>10</sub>: A Chiral Gold Catenane Nanocluster with Zero Confined Electrons. Optical Properties and First-Principles Theoretical Analysis
We
report facile synthesis of the Au<sub>10</sub>(SG)<sub>10</sub> nanoclusters,
where SG stands for glutathione, found to be promising
as a new class of radiosensitizers for cancer radiotherapy. The homoleptic
catenane structure with two Au<sub>5</sub>SG<sub>5</sub> interconnected
rings, among different isomer structures, gives the best agreement
between theoretical and experimental optical spectra and XRD patterns.
This catenane structure exhibits a centrosymmetry-broken structure,
resulting in enhanced second harmonic response and new characteristic
circular dichroism signals in the spectral region of 250–400
nm. This is the first determination of the nonlinear optical properties
of a ligated cluster with an equal Au-to-ligand ratio, thus without
a metallic core and therefore zero confined electrons. Insight into
the nonlinear and chiroptical efficiencies arising from interplay
between structural and electronic properties is provided by the TD-DFT
approach