Electro-optical and optical-optical switching of dual microring resonator waveguide systems

We present design and simulation results on two types of inplane, resonant 2 x 2 optical switches in the strip-waveguided silicon-on-insulator (SOI) system. Both switches are intended for cascading into N x N matrices, and the intersecting strips in the second floating ring switch facilitate construction of an N x N crossbar cross-connect. We examine complex index perturbations of both rings due to electrical injection of free carriers into the rings or to the generation of electron-hole pairs induced by above-bandgap control light focused upon the rings. Switching behavior produced by free-carrier-plasma dispersion, Franz-Keldysh, quantum-confined Stark, Kerr, and thermooptic effects are investigated and compared at the 1.33, 1.55, and 10.6 mu m wavelengths. A study of design tolerances and their consequences shows that the 10.6 mu m wavelength is preferred from the standpoint of photolithographic feasibility and the stronger carrier-optic effect. The SOI high index contrast requires small coupling gaps for the 1.33 and 1.55 mu m wavelengths, which in turn necessitates a high photolithographic precision.