High-Q photonic crystal surface-mode cavities on crystalline SOI structures

High-Q side-coupled surface-mode cavities in two-dimensional (2D) photonic crystals on crystalline silicon-on-insulator (SOI) structures are demonstrated. One of the surface-mode cavities has the measured system Q factor and intrinsic Q factor of 6200 and 13,400, respectively. The experimental results show that the value of system Q factor is ten times and the intrinsic Q factor six times higher than those of similar structures on amorphous SOI structures, respectively, due to the intrinsic material loss is much lower for crystalline silicon. The Q factors of cavities can be further improved by spin-on-glass overlayers, for increasing the structural symmetry. After the spin-on-glass process, the system Q factor and the intrinsic Q factor become nearly twice higher. Meanwhile, the drop wavelengths are largely red-shifted.