Tailoring surface plasmon-exciton polariton for high-performance refractive index monitoring

Abstract

We report coupling between surface plasmon polariton (SPP) and surface exciton polariton (SEP) as hybrid mode; surface plasmon exciton polariton (SPEP) that can be utilized for highly sensitive and accurate refractive index monitoring. The proposed structure comprises of a thin layer of organic semiconductor; J-aggregate cyanine dye (5,5′,6,6′-tetrachloro-1,10-diethyl-3, 30-di(4-sulfobutyl) benzimidazolo-carbocyanine (TDBC)) having, strong dipole moment resulting from linear chain-like structure, over plasmon active metal coated on prism. It is found that due to SPEP excitation, the sensitivity of the proposed refractometer is ∼84% higher as compared to that of conventional plasmonic sensor at λ = 532 nm and has high tolerance towards 10 nm of metal thickness. The wavelength dependent performance analysis of SPEP modes reveals that for high energy SPEP (mode-1 at λ = 532 nm), sensitivity as well as figure of merit (FOM) of the proposed refractometer is ∼80% and ∼200% respectively higher than low energy SPEP (mode-2 at λ = 633 nm). We believe that the study will open a new window for a diverse range of biochemical and gaseous sensing applications.