Hybridizing whispering gallery modes and plasmonic resonances in a photonic metadevice for biosensing applications [Invited]

Measuring the shift in the resonance wavelength of a high-Q dielectric whispering gallery mode resonator in the presence of a modified dielectric environment is a prime sensing strategy. To improve the sensitivity, means have to be identified that push the mode profile outside the resonator to enhance its interaction with the environment. Here, we study theoretically and numerically a photonic metadevice consisting of gold nanoparticles at a high concentration deposited on top of a microdisk resonator. Careful spectral tuning of the plasmonic resonance relative to the whispering gallery mode increases the sensitivity to a notable extent at an acceptable simultaneous decrease of the quality factor. Contrary to comparable approaches that rely on thin metallic films, which require in their fabrication an unprecedented precision, our metamaterial-inspired approach is robust against fabrication imperfection as the only critical parameter is the nanoparticle density.