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.

Simple model for estimating band edge wavelengths of selective reflection from cholesteric liquid crystals for oblique incidence.

A simple model for estimating band edge wavelengths of selective reflection from cholesteric liquid crystals (CLCs) for oblique incidence is proposed. The proposed model and calculation method are based on a geometrical optics model and Bragg's law. Average refractive indices and Bragg angles in a CLC for the short- and long-wavelength edges of a reflection band are calculated using the model.

Luminescent color control of Langmuir-Blodgett film by emission enhancement using a planar metal layer.

A metal enhanced emission of more than 20-fold is observed from a Langmuir-Blodgett (LB) monolayer on a planar aluminum layer with a polymer spacer. The spectral change of the metal enhanced emission using the metal layer is discussed experimentally and theoretically. Finite-difference time-domain simulations and transfer matrix calculations have been performed to investigate the cause of the enhancement.

Wavelength and bandwidth tunable photonic stopband of ferroelectric liquid crystals.

The chiral smectic C phase of ferroelectric liquid crystals (FLCs) has a self-assembling helical structure which is regarded as a one-dimensional pseudo-photonic crystal. It is well known that a stopband of a FLC can be tuned in wavelength domain by changing temperature or electric field. We here have demonstrated an FLC stopband with independently tunable wavelength and bandwidth by controlling temperature and incident angle.

Effective viscosity for nematic-liquid-crystal viscosity measurement using a shear horizontal wave.

We investigate the effective viscosity of a nematic-liquid-crystal (NLC) for viscosity measurement using a shear horizontal (SH) wave propagating through a glass substrate loaded with the NLC. The phase measurement of the SH wave determines the NLC viscosity because SH wave propagation depends on loaded material viscosity. Using this viscosity measurement, we can also determine the viscosity anisotropy of the NLC with director reorientation.