Today, CMOS Photonics technology has matured so that most waveguide based optical functions are vailable inside a CMOS die. While an integrated light source is still an outstanding problem, photodetection can be accomplished by the addition of pure germanium photodetectors to the CMOS process. These components have the potential to enable outstanding sensitivity levels when integrated monolithically with CMOS circuitry.
Gunn C, Masini G, Witzens J, & Capellini G (2006). CMOS Photonics Using Germanium Photodetectors. In SiGe and Ge: Materials, Processing, and Devices - (pp.17) [10.1149/1.2355790].