Microbubble‐Integrated Polymer Fiber Lasers for Multispectral Sensing on Chip

Abstract Photonic fibers have been developed into microlasers for various applications for its outstanding optical properties serving as a whispering‐gallery‐mode (WGM) resonator. Meanwhile, photonic fibers made from polymers are gaining attention due to their strong flexibility and cost‐effectiveness. However, their inherently low refractive index typically results in lower performance for polymer fiber‐based WGM microlasers in aqueous environments, limiting their use in biological applications. In this study, microbubbles are embedded within PMMA fiber, creating the flexible PMMA fiber microbubble laser. This structure led to a remarkable improvement in the microlaser's Q‐factor, increasing it ≈200‐fold and enabling stable functionality within aqueous biological environments. The fiber microbubble laser is further integrated into a microfluidic chip for multiplexed biomarker analysis in serum, achieving a detection limit for Immunoglobulin G (IgG) as low as 6.11 attomolar (aM). This microlaser can have promising applications in fundamental biological research is believed, marking a significant advancement in biosensing technology.