Study of the monolithic integration of sub-bandgap detection, signal amplification and optical attenuation on a silicon photonic chip

We report the development of a silicon integrated circuit that combines conventional electronic circuitry with all-silicon optical waveguides, detectors and modulators. The circuit functions as an optical channel power leveller by amplifying current from a photodetector and feeding that current back to a modulator on the same waveguide. This article describes the use of local oxidation of silicon (LOCOS) for optical waveguide fabrication, the use of deep diffused wells to ensure electrical isolation between the forward biased modulator and detector diodes, and defect-engineering of the photodiodes to give them sufficient responsivity at the operating wavelength of 1.55 μm.