Thermo-optically tunable linear photonic crystal microcavities in advanced SOI CMOS technology

Abstract

We demonstrate linear photonic crystal (PhC) microcavities with thermo-optic tuning capability realized in the IBM 45nm (12SOI) silicon-on-insulator CMOS microelectronics fabrication process. The PhC microcavities can be used as efficient integrated optical wavelength add-drop filters. The cavity is created in the monocrystalline silicon transistor body layer of the CMOS process, with a resonance wavelength of 1520 nm. The cavity device layer is doped to lower the electrical resistance so that current sent through it generates local heating with reasonable drive voltages. The dissipated heat increases the temperature of the cavity and, because of the high thermo-optic coefficient of silicon, increases the index of refraction, shifting the resonance wavelength. This method should be more effective than an adjacent metal or polysilicon heater because the hot spot is right in the middle of the optical mode of the cavity.