Plasmon‐Coupled GaN Microcavity for WGM Lasing and Label‐Free SERS Sensing of Biofluids

Abstract A signal amplification strategy is always required to improve sensing performance, especially for mass‐prepared, miniature and highly sensitive testing equipment. Herein, an on‐chip integrated biosensor combining microcavity lasing and surface enhanced Raman scattering (SERS) for label‐free biochemical analysis is developed. The gallium nitride (GaN) microrings array is fabricated as a whispering gallery mode microlaser based on totally internal wall reflection, and gold nanoparticles (AuNPs) are further assembled on the cavity surface to confine the optical field synergistically. The improvement of lasing capability indicates the strong light‐matter interaction that is conducive to superior response of biomolecules. As a functional example, a GaN/AuNPs substrate is employed in a urine assay, which avoids the shortcomings of requiring specific reactive reagents on different display modules. Ultimately, the chip not only realizes a wide range of pH (3.6–7.8) identification depending on the ultra‐sensitivity feedback of lasing to the refractive index of liquids, but also significantly enhances SERS signals to enable real‐time determination of the biomolecules in human urine. Even the lowest levels of creatinine (0.02%) can be quantitatively detected in less than a minute; thus this work with dual‐mode spectral analyses realizes rapid diagnosis for urinary systems, as well as provides a more accurate reference for the screening of other diseases.