Engineering rainbow trapping and releasing in ultrathin THz plasmonic graded metallic grating strip with thermo-optic...

In this paper, we propose an ultrathin THz plasmonic metallic strip based on graded grating structure with thermo-optic material, which exhibits a strong engineering of trapping and releasing electromagnetic waves in terahertz regimes. The dispersion properties of the ultrathin spoof slow-wave plasmonic graded grating waveguide are characterized using the finite element method, and the propagation characteristics of the grating structures are thoroughly analyzed by the dispersion curves, electric field magnitude distribution, and electric field vertical distribution. The gradient grating waveguide is demonstrated to be an ideal slow-wave system for trapping and releasing surface plasmon polaritons (SPPs) waves through tuning the refractive index of the thermo-optic material. The reflected location for the SPPs waves on the graded corrugated metal strip at 1.1 THz at different temperatures are compared. It is proved that such ultrathin gradient grating waveguide provides an excellent performance for trapping and releasing surface waves at THz, which permits applications for future optical communications.