A plasmonic colour filter and refractive index sensor applications based on metal?insulator?metal square -ring cavities

In this paper, we proposed dual applications of a metal?insulator?metal (MIM) waveguide (WG) resonator design for filtering white light into individual colours and refractive index sensing applications. Six square -ring cavities of different sizes are side coupled to the MIM bus WG. By careful selection of the cavity size and distance between the bus WG and -ring cavities, the resonator can selectively couple to the intensity maxima of different photonic modes and, as a result, preferentially select any of the primary colours. The spectral characteristics of the resonator are comprehensively studied by varying the geometric parameters using the finite element method. This design can offer a sensitivity of 700?nm/RIU, with a figure of merit of 191.6.