Techniques, systems, and devices are disclosed to provide on-chip integrated gas sensor based on photonic sensing. For example, a sensing device is provided to include an optical comb generator that produces an optical comb of different optical comb frequencies in a mid-infrared (MIR) spectral range to interact with a sample under detection, the optical comb generator including a substrate, an optical resonator formed on the substrate and an optical waveguide formed on the substrate and coupled to the optical resonator, and an optical detector that detects light from the sample at the different optical comb frequencies.