Terahertz polarization controller based on electronic dispersion control of 2D plasmons

We numerically investigated the possibility of terahertz polarization controller based on electronic dispersion control of two dimensional (2D) plasmon gratings in semiconductor heterostructure material systems. Taking account of the Mikhailov's dispersive plasmonic conductivity model, the electromagnetic field emission properties of the gated 2D plasmon gratings were numerically analyzed with respect to the density (n) of electrons by using in-house Maxwell's FDTD (finite difference time domain method) simulator. When n is low under a constant drift-velocity condition, the fundamental plasmon mode is excited, being coupled with the radiative zeroth mode of transverse electric (TE) waves. When n exceeds a threshold level, the second harmonic mode of plasmon is predominantly excited, being coupled with the non-radiative first mode of TE waves. We numerically demonstrated that if a grating mesh of 2D plasmons is formed where two independent 2D plasmon gratings are combined orthogonally, the structure can act as a polarization controller by electronically controlling the two axial plasmonic dispersions.