Abstract
We first report a simple nanoplasmonic sensor for both universal and slow-light sensing in a Fano resonance-based waveguide system. A theoretical model based on the coupling of resonant modes is provided for the inside physics mechanism, which is supported by the numerical FDTD results. The revealed evolution of the sensing property shows that the Fano asymmetric factor p plays an important role in adjusting the FOM of sensor, and a maximum of ~4800 is obtained when p = 1. Finally, the slow-light sensing in such nanoplasmonic sensor is also investigated. It is found that the contradiction between the sensing width with slow-light (SWS) and the relevant sensitivity can be resolved by tuning the Fano asymmetric factor p and the quality factor of the superradiant mode. The presented theoretical model and the pronounced features of this simple nanoplasmonic sensor, such as the tunable sensing and convenient integration, have significant applications in integrated plasmonic devices.
Highlights
Since the surface plasmons (SPs) can overcome the diffraction limit and manipulate light in nanoscale domain, they provide possibility for nanodevices with extraordinary properties, high miniaturization and integration[1]
Huang et al reported an enhanced sensor in a plasmonic waveguide[14], and Wen et al studied the sensing with slow light in a fiber Bragg grating[15]
We show a nanoplasmonic sensor based on the Fano resonance in a MDM waveguide systematically, it can be applied for both the universal and the slow-light sensing
Summary
Since the surface plasmons (SPs) can overcome the diffraction limit and manipulate light in nanoscale domain, they provide possibility for nanodevices with extraordinary properties, high miniaturization and integration[1]. Large amount of researches have been devoted to generating the Fano resonances and studied the related sensing properties in various plasmonic structures[6,7,8,9,10], such as nanoparticle clusters[6], metamaterials[7], and non-concentric cavity[8] in the past several years As another special property of the Fano resonance, the light speed in a Fano system can be significantly slowed down due to the steep phase dispersion[11,12], which can enhance the light intensity by reason of the pulse compression. Still little attention is paid to the theoretical research on tuning both the universal and the slow light sensing properties in cavity coupled MDM waveguide system. The superradiant cavity couples with the subradiant cavity through the evanescent field of SPs
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