Design of photonic crystal directional couplers for electro-optical wavelength switching in Si technology

Electro-optical wavelength switch in Si technology operating around = 1.55 µm and based on a photonic crystal directional coupler configuration was studied using Plane Wave Method and Finite Difference Time Domain simulations. Owing to the exploitation of slow wave supermodes, ultra-compact active devices (~ 20 µm) exploiting free carrier plasma dispersion effect in Si can be designed. Injection of input/output strip access waveguides with the photonic core area is optimized using tapering stages to gradually reduce light group velocity. With carrier injection around 1018 cm-3, the coupler configuration can be used as an optical switch of individual wavelengths or a multiplexer/demultiplexer device with active routing of wavelengths.