Single channel high transmission optical band-pass filter based on plasmonic Nano-cavities

This paper is concerned with the investigation of an optical band-pass filter based on sub-wavelength surface plasmon polariton. The transmission characteristics are numerically analyzed by the finite difference time domain method and simulation results reveal that the structure has a band-pass filtering characteristic. The metal-insulator-metal plasmonic nanostructure is implemented by several vertical rectangular cavities across an optical waveguide. The metal and dielectric materials utilized for the realization of the filter are silver and air, respectively. Furthermore, the performance can be efficiently modified by tuning the geometric parameters such as the cavities' length and width and the coupling distance between them. The output transmission spectrum shows a single transmission peak over a wide wavelength range of 400 nm to 2000 nm while the full width at half maximum is about 200 nm. The high extinction ratio beyond 40dBc with the low insertion loss make this filter comparable to those of other proposed band-pass filters. Besides, the operating wavelength of this filter can be expeditiously tuned by adjusting the geometric parameters, mainly the length of the center cavity. The small footprint of the structure contributes to the achievement of wavelength selection systems for optical communications in ultra-dense plasmonic integrated circuits.