Directional Scattering of Semiconductor Nanoparticles Embedded in a Liquid Crystal

Real-time measurement of the liquid-crystal optic-axis angle and effective refractive index distribution based on a common-path interferometer

A common-path interferometer for the real-time measurement of the liquid-crystal (LC) optic-axis angle and effective refractive index distribution is proposed. This method involves adding a polarizer and polarization camera to a general optical microscope. This requires only single-exposure imaging without changing any optical elements, and greatly simplifies the measurement process and system. In addition, the measurement results are unaffected by light-source power fluctuations or a non-uniform spatial distribution. Therefore, this method is suitable for measuring the LC optic-axis angle and effective refractive index of electrically controlled LC devices. Finally, the feasibility and validity of the proposed method are verified by simulation and experimentation.

Recent Advances in Adaptive Liquid Crystal Lenses

An adaptive-focus lens is a device that is capable of tuning its focal length by means of an external stimulus. Numerous techniques for the demonstration of such devices have been reported thus far. Moving beyond traditional solutions, several new approaches have been proposed in recent years based on the use of liquid crystals, which can have a great impact in emerging applications. This work focuses on the recent advances in liquid crystal lenses with diameters larger than 1 mm. Recent demonstrations and their performance characteristics are reviewed, discussing the advantages and disadvantages of the reported technologies and identifying the challenges and future prospects in the active research field of adaptive-focus liquid crystal (LC) lenses.

Silicene Quantum Dots: Synthesis, Spectroscopy, and Electrochemical Studies

Organically functionalized silicene quantum dots (SiQDs) were synthesized by chemical exfoliation of calcium silicide and stabilized by hydrosilylation with olefin/acetylene derivatives forming Si-CH₂-CH₂- or Si-CH═CH- interfacial bonds. Transmission electron microscopy and atomic force microscopy measurements showed that the resultant SiQDs were ca. 2 nm in diameter and consisted of ca. four atomic layers of silicon. The structure was further characterized by ¹H and ²⁹Si NMR and X-ray photoelectron spectroscopic measurements. In photoluminescence measurements, the SiQDs exhibited a strong emission at 385 nm and the intensity varied with the interfacial linkage. In electrochemical measurements, both ethynylferrocene- and vinylferrocene-functionalized SiQDs exhibited a pair of well-defined voltammetric peaks at +0.15 V (vs Fc⁺/Fc) in the dark for the redox reaction of the ferrocene/ferrocenium couple; yet under UV photoirradiation, an additional pair of voltammetric peaks appeared at -0.41 V, most likely because of the redox reaction of ferrocene anions formed by photoinduced electron transfer from the SiQD to the ferrocene metal centers.

Electromagnetic polarization-controlled perfect switching effect with high-refractive-index dimers and the beam-splitter configuration

Sub-wavelength particles made from high-index dielectrics, either individual or as ensembles, are ideal candidates for multifunctional elements in optical devices. Their directionality effects are traditionally analysed through forward and backward measurements, even if these directions are not convenient for in-plane scattering practical purposes. Here we present unambiguous experimental evidence in the microwave range that for a dimer of HRI spherical particles, a perfect switching effect is observed out of those directions as a consequence of the mutual particle electric/magnetic interaction. The binary state depends on the excitation polarization. Its analysis is performed through the linear polarization degree of scattered radiation at a detection direction perpendicular to the incident direction: the beam-splitter configuration. The scaling property of Maxwell's equations allows the generalization of our results to other frequency ranges and dimension scales, for instance, the visible and the nanometric scale.

Traditional metallic communication elements suffer from substantial losses in the visible and near-infrared. Here, Barreda et al. show in a proof of principle in the microwave regime that a pair of high-index dielectric spheres can operate as a perfect switch in a beam-splitter configuration.