Design and Simulation of a Terahertz Frequency Filter Based on Plasmonic SIS Waveguide Coupled with a Split Ring Resonator for Refractive Index Sensing Applications

Terahertz waveguides and resonators have brought numerous applications from biomedical to modern communications. In this paper, we have demonstrated numerically a straight semiconductor-insulator-semiconductor(SIS) waveguide attached to a split ring resonator, which acts as a terahertz frequency filter and can be used for refractive index sensing. The device's transmission properties have been studied using the finite element method. To fix the third dimension of the device, that is the depth of the waveguide the effective mode index and power density calculations are done for the propagating mode. The frequency tuning of the filter is achieved by changing the geometric parameters of the waveguide and resonator system such as ring radii and split width. Both the symmetric and antisymmetric modes of the split ring show almost the same rate of change of resonance frequency with the change in geometric parameters. To demonstrate the importance of the split position, the transmittance is studied by placing the split at different positions on the ring. We obtained the same transmittance for the split at left and right positions, whereas the split at the top and bottom shows different transmittance similar to the transmittance of a ring resonator. The symmetric and antisymmetric modes of the split ring are calculated for refractive index sensing and the highest sensitivity of 0.741 THz/ refractive index unit (RIU) for the symmetric mode as expected.

Automated summary

This paper presents a terahertz frequency filter consisting of a split ring resonator and a semiconductor-insulator-semiconductor (SIS) waveguide. The device's transmission properties are studied using the finite element method, and the frequency tuning of the filter is achieved by changing the geometric parameters. The importance of the split position is demonstrated by studying the transmittance at different positions on the ring.