High-performance optical sensing based on electromagnetically induced transparency-like effect in Tamm plasmon multilayer structures

We present a novel kind of optical sensor based on the electromagnetically induced transparency (EIT)-like effect in a Tamm plasmon multilayer structure, which consists of a metal film on a dielectric Bragg grating with alternatively stacked TiO₂ and SiO₂ layers and a defect layer. The defect layer can induce a refractive-index-sensitive ultranarrow peak in the broad Tamm plasmon reflection dip. This nonintuitive phenomenon in analogy to the EIT effect in atomic systems originates from the coupling and destructive interference between the defect and Tamm plasmon modes in the multilayer structure. Taking advantage of this EIT-like effect, we achieve an ultrahigh sensing performance with a sensitivity of 416 nm/RIU and a figure of merit (FOM) of 682 RIU⁻¹. The numerical simulations agree well with the theoretical calculations. Additionally, the spectral line shape can be effectively tailored by changing the defect layer thickness, significantly promoting the dimensionless FOM from 0.76 × 10⁴ to more than 2.4 × 10⁴. Our findings will facilitate the achievement of ultrasensitive optical sensors in multilayer structures and open up perspectives for practical applications, especially in gas, biochemical, and optofluidic sensing.