Wave phase analysis for computing density of states, group velocity, and lateral shift in a 1D quasiperiodic...

In this paper, by considering wave phase analysis, the density of modes, group velocity, and lateral shift in one-dimensional multilayer are theoretically computed by using the transfer matrix method in the terahertz domain. The proposed structure is based on the Fibonacci sequence constituted of uniaxial indefinite medium and SiO₂ layers. It is found that for both TE and TM beams, around an angle of 90º, the lateral shift is highly negative, while it is positive at the rest of the angles. Also, for non-vertical angles, a positive peak is observed about an angle of 60º (near the Brewster angle). Our numerical analysis shows that at angles less than about 10º, the lateral shift is negative for the TM mode. It is shown that for both polarizations the density of states (the group velocity) has maximum (minimum) value near the band gap edges, while inside the band gap it becomes minimum (maximum). Superluminal and subluminal cases can be defined here.