Resonance-Based Optical Gas Sensors

Gas sensors play a critical role in numerous human activities. Their necessity continues to grow across diverse fields as technological advancements drive demand for precision agriculture and bioengineering among other applications. Among existing sensor technologies, optical gas sensors stand out due to their ability to operate remotely in high-risk environments while remaining unaffected by electromagnetic interference. Resonance-based optical sensors offer targeted gas detection through the functionalization of their sensitive surfaces. This work focuses on reviewing the state of the art in resonance-based optical gas sensors (ROGS), addressing their fundamental principles, recent advances in fabrication processes, waveguide designs, and materials employed both for resonance generation and as sensitive coatings. Additionally, the review examines achieved sensitivity, emerging applications, and key developments in the field, including those efforts on improving ROGS performances by means of artificial intelligence (AI) techniques. The study encompasses optical sensors leveraging Surface Plasmon Resonance (SPR), Lossy Mode Resonance (LMR), and Hyperbolic Mode Resonance (HMR)—the latter representing a notable breakthrough in recent years as a particular case of Bloch Surface Waves (BSWs).