Ternary comb-like silicon photonic crystal: Oxidation, intrinsic modes, reflection windows and contrastivity
A ternary photonic crystal - A/B/A/C periodic structure is investigated analytically and numerically in the framework of transfer matrix formalism. The influence of oxidation to photonic gaps and positions of reflection windows for (SiO2/Si/SiO2/Air)N structure is calculated. It was shown that intrinsic optical contrastivity has a non-monotone behavior during the process of oxidation of silicon. The found results will allow to determine the optimal regimes of oxidation to obtain needed photonic device properties.
Optical contrastivity of complicated materials: finite layered structures
Abstract
We define the intrinsic optical contrastivity of a complicated layered
structure as the relative total gap taken inside the total
internal reflection region over a chosen range of frequencies. The notion
introduced for ordered 1D systems retains its meaning for 2D and 3D ordered optical
systems, as well as for disordered structures. The parametric maps of contrastivity and
sensitivity are calculated for 1D comb matrices based on glass, silicon, and microporous
silicon with various fillings, comb sizes, and densities of a gaseous filling. The
existence of areas on a parametric map which are highly sensitive to deviations in the
contrastivity is shown for different materials. In the case of a gaseous filling of voids
between the matrix material layers, the areas of a very high sensitivity are also found.

Characterization of a tube-in-shell thermosyphon heat exchanger for solar water heating
Performance of a double-wall, natural convection, two-pass, tube-in-shell heat exchanger designed for use in a solar water heating system is measured. The heat exchanger is mounted along the length of a solar water storage tank. Flow of cold water on the shell side of the heat exchanger is driven solely by buoyancy forces. Hot side fluid is pumped. Flow rate, pressure drop and temperature data needed for a semi-empirical model of the heat exchanger are obtained. Performance is measured for forced convection, hot side volumetric flow rates of 0.016, 0.032 and 0.079 l/s. Temperature difference between hot and cold fluid at the inlets is varied from 0 to 75 degC. Measured values include thermosyphon and forced flow rates, temperature differences across the beat exchanger, vertical temperature distribution in the storage tank, and pressure drop due to shear on the thermosyphon side of the heat exchanger. Heat exchanger effectiveness and overall heat transfer area product (UA) are calculated. Thermosyphon mass flow rates are on the order of 0.01 kg/s. Although the low flow rates create thermal stratification of the water storage tank, they restrict energy transfer in the heat exchanger.