Nanophotonic technology has emerged to seamlessly integrate state-of-the-art optical devices on microchips by leveraging the existing complementary metal-oxide semiconductor infrastructure to fabricate photonic integrated circuits at a low cost. Photonic integrated circuits offer attractive solutions in data capacity, latency, and power consumption by incorporating hundreds of discrete optical components onto a compact chip. Moreover, the usage of optical microcavities with high quality factors enhances the light-matter interaction while maintaining small footprints for both linear and nonlinear photonic applications. This dissertation focuses on silicon and silicon carbide based photonic devices for sensing, electro-optic modulation, and signal processing.