Dielectric waveguide vertically coupled to all-silicon photodiodes operating at telecommunication wavelengths

We present a method for detecting light in the 1550 nm wavelength window based on a silicon nitride waveguide that is vertically coupled to a silicon photonic crystal cavity. The absorption in silicon arises from deep-levels created by ion implantation, thereby providing excellent CMOS compatibility. We demonstrate a responsivity of 0.108 A/W at −10 V reverse bias with a dark current of 9.4 nA. Our work demonstrates one of the smallest wavelength selective photodectors realised to date. By cascading such detectors we also demonstrate a two-channel demultiplexer.