“…Though compact Raman sensors are available, on-chip Raman spectroscopy is ultimately desired because of its ability to be integrated into a complete and miniaturized device package. Among different platforms, photonic circuits have the advantages of integrating on-chip light sources, detectors, and wavelength demultiplexing components, − all in one module through grating couplers − and microresonators. − Thus, the material selection of the optical waveguide, the key element of photonic circuits, is critical and requires unique material features of high refractive index, low autofluorescence, and low Raman noise floor. In addition, a waveguide with proper design can form a strong evanescent field, which not only enhances the interaction between the excitation light and the analytes but can improve the Raman scattering efficiency to enable accurate Raman sensing. − …”