Sensitivity Enhancement of Silicon Strip Waveguide Ring Resonator by Incorporating a Thin Metal Film

In this work, we proposed a metal-assisted silicon strip waveguide design for highly sensitive refractive index sensing applications. To prove the superiority of our proposed design, we make a fair comparison with the standard silicon strip waveguide of comparable geometry. In metal-assisted waveguide structure, a thin SiO
₂
layer is sandwiched between gold and silicon strip waveguide. The transmission spectrum and E-field distribution of these structures are simulated using 3D-Finite Element Method (FEM). In the first part of the paper, we demonstrated the enhancement of the evanescent field in the upper cladding region of a straight strip waveguide which makes it an ideal candidate for evanescent field gas absorption sensor. In the second part, we designed a metal-assisted silicon strip waveguide ring resonator of radius 1.5 μm and verified its higher sensitivity, Q-factor and figure of merit compared to standard ring resonator. The maximum sensitivity of 300 nm/RIU is obtained which is ~67% higher than the sensitivity of a standard ring resonator design when sandwiched SiO
₂
layer is equal to 50 nm in our proposed design. We believe that our study will provide new favourable circumstances to design sensors with improved sensitivity.