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.

rPET detectors design and data processing
Small animal PET systems based on rotating planar detectors posses some interesting advantages for high sensitivity, high resolution imaging. We have designed the rPET detectors based on MLS crystals assembled on a 30times30 matrix optically coupled to a flat-panel PS-PMT. Weighted position readout circuits pre-process the 64 signals from the 8times8 anodes matrix, which are digitized using a charge-integrating converter. The amplification electronics, including the trigger output for coincidence detection, and the high voltage supply are integrated in a three PCBs stack that forms the base attached to the back of the PMT. The whole assembly is enclosed in a light tight, lead (Pb) shielded aluminum box. The detectors are mounted on a rotating gantry with more than 180 degrees rotation span. The digitized events are screened and histogramed, and a modified center of gravity algorithm removes from the position calculation those signals with poor signal to noise ratio. Apparent mean crystal size on the 511 keV field-flood images is 0.6 mm, mean peak-to-valley ratio is better than 8, and intrinsic resolution is 1.5 mm at the central row, with the energy window wide open. Sensitivity (CPS) for a pair of these detectors set in coincidence at 160 mm distance is 1%