Structural colors of pearls

The luster is the most important characteristic of pearls, whose colors depend on periodic structures of aragonite crystal layers and conchiolin sheets. We here propose an optical model for analyzing the structural colors of pearls that includes the transmission, reflection, and scattering of light in pearls. Unlike other structural color materials, internal light scattering and its transmission are the keys to understanding the optical properties of pearls. The appearance of pearls is determined by the superposition of transmitted and reflected light. The transmission and reflection spectra of pearls calculated using the proposed model show good agreement with experimental results. We also demonstrate the rendering of images of pearls using the calculated spectra. Furthermore, the appearance of pearls with different layer thicknesses are predicted by calculation based on the optical model.

Coherent characterisation of a single molecule in a photonic black box

Extinction spectroscopy is a powerful tool for demonstrating the coupling of a single quantum emitter to a photonic structure. However, it can be challenging in all but the simplest of geometries to deduce an accurate value of the coupling efficiency from the measured spectrum. Here we develop a theoretical framework to deduce the coupling efficiency from the measured transmission and reflection spectra without precise knowledge of the photonic environment. We then consider the case of a waveguide interrupted by a transverse cut in which an emitter is placed. We apply that theory to a silicon nitride waveguide interrupted by a gap filled with anthracene that is doped with dibenzoterrylene molecules. We describe the fabrication of these devices, and experimentally characterise the waveguide coupling of a single molecule in the gap.

Windows-based computational algorithms for 1D MPC and thin-film analysis

The development of magnetic photonic crystals (MPC) has been a rapidly evolving research area since the late 1990s. Magneto-optic (MO) materials and the techniques for their characterization have also continually undergone functional and property-related improvements. MPC Optimization is a feature-rich Windows software application designed to enable researchers to analyse the optical and magneto-optical spectral properties of multilayers containing gyrotropic constituents. A set of computational approaches, and a custom software package have been described, designed to enable the design and optimization of 1D magnetic photonic crystals in terms of the achievable combinations of Faraday rotation, transmission, and reflection spectra. 

Windows-based computational algorithms for 1D MPC and thin-film analysis

The development of magnetic photonic crystals (MPC) has been a rapidly evolving research area since the late 1990s. Magneto-optic (MO) materials and the techniques for their characterization have also continually undergone functional and property-related improvements. MPC Optimization is a feature-rich Windows software application designed to enable researchers to analyse the optical and magneto-optical spectral properties of multilayers containing gyrotropic constituents. A set of computational approaches, and a custom software package have been described, designed to enable the design and optimization of 1D magnetic photonic crystals in terms of the achievable combinations of Faraday rotation, transmission, and reflection spectra. 

Влияние дефектов на поглощение терагерцового излучения в монокристалле CdSiP-=SUB=-2-=/SUB=-

Measurements of the transmission and reflection spectra of a CdSiP2 single crystal, performed in the temperature range from 80 to 300 K using pulsed terahertz and infrared Fourier spectroscopy, revealed a significant impact of post-growth defects on absorption in the THz range. It was found that this absorption is weakly dependent on temperature, in contrast to the previously obtained results for another crystal of the chalcopyrite family with s significantly lower concentration of defects. When cooling, the intrinsic absorption mechanisms were minimized and the contribution of defects to absorption was extracted

Pulsed Laser Annealing Effect on Optical and Structural Properties of ZnS/ZnSe Heterostructures

Studies of pulsed laser annealing (PLA) on semiconductor thin films were performed to examine changes of the optical and structural parameters due to the laser heat. Thin films of ZnS/ZnSe were deposited on quartz substrates at a pressure of 8.2*10-6 mbar using PVD technique. These thin films were annealed at different laser powers using CO2 pulsed laser. Transmission and reflection spectra were recorded before and after the annealing process. A decrease in the transmission and reflection spectra after annealing is observed. The absorption coefficient, refractive index, damping coefficient and dielectric constant were calculated before and after the annealing process. Changes in the optical parameters are found after the annealing process. The energy band gaps of ZnS and ZnSe have been determined. Upon annealing, an increase in the absorption coefficient is observed which is due to an improvement in the granular nanostructure of the ZnS/ZnSe thin films. XRD patterns of the prepared samples were obtained before and after the annealing procedure and revealed an enhancement in the crystallite structure upon annealing.

Оптические свойства многослойных пленочных структур BaTiO-=SUB=-3-=/SUB=-/SiO-=SUB=-2-=/SUB=-, сформированных золь--гель-методом

Multi-layer film structures BaTiO_3/SiO_2 with a thickness of ~1 μm containing up to 14 pairs of layers were synthesized by the sol–gel method with sequential heat treatment. It is shown that the synthesized structures are X-ray amorphous. The formation of bands in the transmission and reflection spectra caused by interference effects is demonstrated. A more regular structure exhibits a photon band gap (opacity band) in the visible range with main minimum at 636 nm and corresponding maximum in the reflection spectra. Dispersion characteristics of barium titanate films with different concentrations of initial sols were studied and an increase in the refractive index with an increase in the concentration of sol was demonstrated. For a sol with a concentration of 60 mg/mL, the refractive index in the spectral range of 390–1600 nm is 1.88–1.81. The prospects of sol–gel technology for the formation of BaTiO_3/SiO_2 structures for nanophotonics and solar radiation converters are discussed.

Электродинамические характеристики alpha-лактозы моногидрата в терагерцовом диапазоне-=SUP=-*-=/SUP=-

Using methods of infrared, terahertz, and submillimeter spectroscopy, experimental transmission and reflection spectra of α-lactose monohydrate have been obtained at room temperature in the frequency range from 5 to 5000 cm^–1. The experimental spectra of dense pressed tablets and powdered samples have been analyzed in terms of the model of a classical oscillator. Certain parameters of absorption bands of the resonant and quasi-relaxation types are markers by which components can be selected in heterogeneous pharmacological and organic preparations using the methods of coherent submillimeter and pulsed terahertz spectroscopy.