Coupling between surface plasmon polariton and planar waveguide modes in the biosensor based on metal–insulator–metal/planar waveguide structure

In this paper, we propose a high performance biosensor which allows the coupling between surface plasmon polariton (SPP) mode in metal–insulator–metal waveguide and planar waveguide (PWG) mode. The reflection curve exhibits a sharp dip originated from PWG mode when there is a weak coupling between SPP and PWG modes. The strong coupling between SPP and PWG modes results in asymmetric Fano resonance and plasmon-induced transparency. The sensitivities of PWG mode dip and Fano resonance achieve 9733 and 7050 RIU−1, respectively, which are enhanced by 2∼3 orders of magnitude compared to those of conventional surface plasmon resonance sensors.