Multi-Narrowband Tunable Plasmonic Induced Transparency for Sensing

We propose and numerically investigate infrared multi-narrowband tunable plasmonic induced transparency and its application as plasmonic sensor. Quasi-guided modes can be excited in Al
₂
O
₃
/SiO
₂
slab waveguide by the plasmonic periodic E shaped metallic nanostructures, which leads to multiple Fano-shaped transmission. The designed nanoparticle/slab waveguide/Si substrate structure exhibits multi-narrowband transparency and high reflectivity, which is easy to prepare and integrate. We further demonstrate electric tunability of multi Fano resonances by the introduction of larger-area graphene in the wavelength range 2000–3000 nm. Considering the multiple narrow bands and electric tunning performances of this structure, it is suitable to be utilized as a sensor. It shows that the figure of merit (FOM*) of the sensor can reach 66548 within the refractive index range 1.3-1.39. Moreover, the plasmonic sensor can also be used as a multiband optical switch with modulation depth up to 70%.