Gradual cross polarization conversion of transmitted waves in near field coupled planar terahertz metamaterials

In this work, we examine gradual cross polarization conversion using two coupled circular split ring resonators (SRRs) in the terahertz (THz) frequency regime. In the proposed geometry, a metamolecule (unit cell) is comprised of two circular split ring resonators having a single split gap. One resonator is rotated with respect to the other from 0 degrees to 180 degrees in the steps of 15 degrees and thereby, co- and cross-polarization components of the transmitted terahertz are investigated. The cross polarization component is observed to be maximum when resonator split gaps are orthogonal to each other; however, in the co polarization resonance, a strong split is observed. Based upon the angle of rotation between the resonators, the study reveals that the cross polarization conversion can be tuned from minimum to maximum and then back to the minimum. We have employed a semi-analytical model to understand the polarization conversion arising from the coupling between the resonators and found that it corroborates numerical findings. The ability to control linear polarization conversions can be significant in the development of THz polarimetric devices. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement