Dual‐Modal Sensing Platform Based on Flexible GaN Microdisk Lasers on PDMS Substrate

Abstract Whispering gallery mode (WGM) micro‐nano resonant cavities have demonstrated significant potential in high‐sensitive sensing applications due to their compact footprint, rapid response, and high Q factor etc. Nevertheless, fabrication of high‐performance WGM devices suitable for multifunctional sensing remains challenging due to complicated fabrication process and material limitations. Furthermore, most existing devices are constrained to a single modal sensing capability and rigid substrate, limiting their multifunctionality and flexibility. This study presents an innovative approach to fabricating GaN‐based microdisks on flexible PDMS substrate via a secondary substrate transfer technique, overcoming critical fabrication challenges. The active microcavity achieves a Q factor up to 10 923. The lasing spectrum in green spectral region can be precisely tuned not only by modulating the strain in the PDMS substrate, but also by altering the refractive index of the surrounding material, showing dual‐modal sensing capability. Experimental results demonstrate that the sensitivity of sensing about the strain and the refractive index are 0.08 nm/mm ⁻¹ and 666.9 nm/RIU, respectively. The detection limit of the refractive index sensor is as low as 5.4 × 10 ⁻⁶ RIU. This study provides a novel dual‐modal flexible sensing platform which is promising in strain sensing, water quality monitoring, laser dynamic modulation, and tactile sensing.