Design for the reconfigurable polarization rotator by inhibiting Fano resonance with graphene-metal grating structures

Abstract

In this paper, the Fano resonance associated with the integrated grating-enhanced transmissive cross-polarization rotator (TCPR) superimposed via two polarization plates operating in disparate frequency bands is observed. The metal resonance frequency dramatically impacts the Fano effect, which triggers alterations in polarization conversion ratio (PCR). Through the analysis for the surface current distributions, the spring vibrator model driven by external forces in two orthogonal directions is employed to figure out the internal mechanism of the Fano line shape in the PCR curve. Subsequently, the symmetrical lateral current branches on the two gold polarization sheets are accessible. The relative bandwidth (RBW) value and the operating region of the ultimate optimized TCPR are 84.6% and 0.563 THz–1.388 THz, respectively. In other words, the PCR band is expanded successfully. Intended to obtain the fabulous polarization switching behavior to enhance the reconfigurability, the gated voltagedriven graphene is doped in grating gaps with the chemical potential fluctuating uniformly between 0.01 and 0.50 eV. The proposed optimizations with the PCR and the final TCPR are distinguished from precedented instances in the RBW and tunability, which is universally applicable in multitudinous terahertz-controlled scenarios.