Gain‐Assisted Active Spoof Plasmonic Fano Resonance for High‐Resolution Sensing of Glucose Aqueous Solutions

Abstract Fano resonance has received much attention in recent years due to its promising applications in surface enhanced phenomena, sensing, and nonlinear optics. However, it is challenging to achieve both high quality (Q) factor and high intensity using the Fano resonance. Different from active switching/tuning of plasmonic Fano resonances, gain‐assisted active spoof plasmonic Fano resonance is for the first time proposed to enhance both the Q factor and resonance intensity significantly, in which a subwavelength amplifier chip is incorporated into a passive plasmonic structure composed of two stacked corrugated metal rings. Experimental results show that the Q factor of the Fano resonance is increased from 49 to 2802, and the resonance intensity is improved from 19.89 to 37.42 dB. The high performance of the active plasmonic structure makes the limit of detection reach to 10 mg dL⁻¹, and thus the minute change of glucose aqueous solutions has been successfully detected.