On-Chip Biosensing and Gas Sensing by Photonic Slot Waveguides: A Review

Photonic slot waveguides enhance light–matter interactions by confining the optical field in regions with a low refractive index, making them highly effective for detecting a wide range of biological and chemical analytes. This article reviews the application of photonic slot waveguides in biosensing and gas sensing, showcasing their ability to be integrated into on-chip platforms often intended for point-of-care testing with enhanced sensitivity and specificity. In biosensing, these waveguides are particularly suited for applications in medical diagnostics and environmental monitoring, allowing for the detection of biomarkers and other biological molecules with high sensitivity. For gas sensing, photonic slot waveguides have been employed effectively in the near-infrared and mid-infrared spectrum to detect various gases, including hazardous and greenhouse gases, which is crucial for both industrial safety and environmental protection. This review also explores the potential of these waveguides in noninvasive diagnostic methods, such as liquid biopsy, breath analysis, and breath biopsy, which offer new avenues for early disease detection and monitoring. By summarizing recent advancements and outlining future directions, this review underscores the transformative potential of photonic slot waveguides in advancing on-chip sensing technologies across multiple fields.