Numerical investigation of a small footprint plasmonic Bragg grating structure with a high extinction ratio

In this paper, miniaturized design of a plasmonic Bragg grating filter is investigated via the finite element method (FEM). The filter is based on a plasmonic metal-insulator-metal waveguide deposited on a quartz substrate. The corrugated Bragg grating designed for near-infrared wavelength range is structured on both sides of the waveguide. The spectral characteristics of the filter are studied by varying the geometric parameters of the filter design. As a result, the maximum ER and bandwidth of 36.2 dB and 173 nm are obtained at lambda(Bragg)=976 nm with a filter footprint as small as 1.0 x 8.75 mu m(2), respectively. The ER and bandwidth can be further improved by increasing the number of grating periods and the strength of the grating, respectively. Moreover, the Bragg grating structure is quite receptive to the refractive index of the medium. These features allow the employment of materials such as polymers in the metal-insulator-metal waveguide which can be externally tuned or it can be used for refractive index sensing applications. The sensitivity of the proposed Bragg grating structure can offer a sensitivity of 950 nm/RIU. We believe that the study presented in this paper provides a guideline for the realization of small footprint plasmonic Bragg grating structures which can be employed in filter and refractive index sensing applications.