Tunable Bragg reflector with parallel bulk Dirac semimetals at terahertz frequencies

Abstract

We propose numerically a terahertz Bragg reflector with two parallel bulk Dirac semimetals (BDSs) sheets separated by alternated dielectric gratings using the finite-difference time-domain (FDTD) method. The transmission of the proposed reflector can be tuned via not only varying the permittivity of the dielectric grating but also changing the period number of the unit cells. By adjusting the separation distance of the parallel BDS sheets, we can derive another degree of freedom to tune the Bragg band gap. In addition, the transmission spectra can also be freely tuned by means of alkaline metal doping. At last, the defect resonant mode is realized in the Bragg reflector. Our proposed Bragg reflector will have potential prospects in designing integrated photonic circuits at terahertz frequencies.