High resonant transmission contrast filter based on the dual side-coupled cavities plasmonic structure

By using indirect coupling between two side-coupled cavities, we propose a method to enhance the resonant transmission contrast ratio in the lossy metal–dielectric–metal waveguide cavity system. We find that the dual side-coupled cavity structure has higher on-resonance transmission contrast ratio than the single side-coupled cavity structure for involving more coherent interfering paths. The filter operating around the wavelength of 1550 nm is analyzed based on coupled-mode theory, and the optimal on-resonance transmission contrast condition is obtained. Numerical experiments confirm the enhancement of the resonant contrast.