Monolithic integration of photonic stack onto CMOS imager for absorption spectroscopy

Herein, we report about the monolithic integration of a unique photonic stack on top of a CMOS imager using a dedicated fabrication process. The system key components consists of silicon nitride (SiNy) optical waveguides, sloped input mirror, grating in/out-couplers, and copper-based vertical mirrors defining the resonator boundaries. The stack is optimized for operation in the NIR range (800–900nm). Up to the authors' knowledge, this is the first demonstration of a fully integrated photonic stack including a sloped metal mirror combined with SiNy waveguide technology. The photonic build-up can be used for various applications among them is absorption spectroscopy as demonstrated hereafter.