Design and Optimization of the Multifunctional Rectangular Cavity Band-Pass Filter Based on the Surface Plasmon Polariton

A novel multifunction filter based on the model of Fabry-Perot (F-P) resonant cavity is proposed in this paper. This filter is comprised of a rectangular cavity (400nmx200nm) and two narrow silicon baffles (40nmx50nm) which are placed next to the cavity separately. Its transmission characteristics are calculated by the numerical simulation software COMSOL Multiphysics which is based on the finite element method (FEM). The results show that with the increase of silicon baffles' length, an apparent red-shift of the transmission peak is observed. Moreover, not only a band-pass filter that the transmission peak can reach almost 90 % but also an excellent flat-top filter can be obtained by properly adjusting the other structural parameters of the rectangular cavity. Meanwhile, the simulation results are verified by the impedance matching (IM) model. The filter proposed in this paper performs well, possesses two functions, and provides a new option for the development of nano-optical devices.