Accordingly, PhC devices in SOI are realized by creating a lattice of air-holes in silicon, which can by achieved by anisotropic etching, of a high resolution patterned surface, into the silicon device layer (top layer of the SOI wafer). The refractive-index modulation, depth, and length of the device are the main parameters that are used to determine the optical properties of devices based on a photonic bandgap. Thus, stringent control of these parameters necessitates high-resolution lithography and high-aspect-ratio etching. While high aspect ratio etching technology is common in the micro- electromechanical systems (MEMS) industry, they typically use sophisticated etching systems.
