We present a new computational method that excites guided phonon modes in nanoscale waveguides at a specific frequency and wavenumber. The method uses nonequilibrium molecular dynamics and Fourier analysis of particle displacements to extract mode shapes from single frequency excitations consisting of superposed spatial modes. These mode shapes are used to excite the waveguide inlet boundary so that single phonon modes are generated in the structure. Mode shapes and phonon spectra for a silicon planar waveguide with rigid wall boundaries are calculated to demonstrate the viability of the technique. This method improves upon molecular dynamics techniques that activate all possible phonon modes and are thus not able to isolate the contribution of any single phonon excitation. Application of our method will enable the computational investigation of single phonon mode propagation in nanostructures of varying geometry.

Various non-invasive glucose monitoring methods using near-infrared spectroscopy have been investigated although no method has been successful so far. Our previous study has proposed a new promising method utilizing numerically generated absorbance spectra instead of the experimentally acquired absorbance spectra. The method suggests that the correct estimation of the optical properties is very important for numerically generating the absorbance spectra. The purpose of this study is to measure the change in the optical properties of the skin with the change in the blood glucose level in vivo. By measuring the reflectances of light incident on the skin surface at two distances from the incident point, the optical properties of the skin can be estimated. The estimation is a kind of the inverse problem based on the simulation of light propagation in the skin. Phantom experiments have verified the method and in vivo experiments are to be performed.

In order to predict the skin colors, we need to analyze the reflection spectra of the skins. For the diffuse reflection, it is essential to know the skin optical properties that describe the propagation of light in the skin. We measure the absorption coefficient μ a , scattering coefficient μ s , scattering phase function p(θ) and refractive index n of human skins in this study. We attempt to build a measurement system which can accurately measure the optical properties of the skin samples with a size of as small as 5 mm and a thickness of as thin as 50 micrometer in the visible wavelength range with the wavelength step of 50 nm. Then we measured the optical properties of stratum corneum obtained from a cultured model of human epidermis and those of epidermis obtained from human skin. The effect of the exposure of epidermis to sunlight on the optical properties is discussed.