Why Slot And Hybrid Plasmonic Waveguides Are Ideal Candidates For Sensing Applications?

In this paper, the modal characteristics of silicon-based optical waveguides (hereafter represented as WGs) such as ridge, rib, slot and the hybrid plasmonic WGs are discussed. For sensing applications, the geometric parameters of the WGs are optimized to evaluate the mode sensitivity (S-mode) and evanescent field ratio (EFR). For highly sensitive devices, these two parameters should be as high as possible to facilitate strong light-matter interaction. The analysis is performed via the finite element method (FEM) which demonstrate that EFR and S-mode follow the following order: Hybrid WG >= Slot WG > Ridge WG @ TE mode > Rib WG @ TE-mode > Ridge WG @ TM mode > Rib WG @ TM mode. Furthermore, refractive index sensor established on a ridge, slot and hybrid plasmonic WGs are studied. The numerical calculations have revealed that the best sensitivity of 167 nm/RIU, 233.3 nm/RIU and 333.3 nm/RIU is delivered by ring resonator designs constructed on ridge, slot and the hybrid plasmonic WG, respectively. We believe that these findings are quite beneficial to have a detailed analysis of different WG types to make a judicious selection of optical WG structure for sensing applications.