Controlling terahertz surface plasmon polaritons in Dirac semimetal sheets

We theoretically investigate the dispersion and coupling characteristics of terahertz surface plasmons polaritons (SPPs) in bulk Dirac semimetals (BDS) sheets, which indicate that symmetric and anti-symmetric modes are attributed to the odd and even superpositions of the anti-symmetric eigenmode supported by the single-layer BDS sheet. Interestingly, the symmetric mode has better confinement than the eigenmode and anti-symmetric mode. By introducing two silicon bars, the highly-confined symmetric mode is modulated in resonance frequency and transmission intensity by the designed novel band-pass filter. Numerical results show good agreement with the theoretical analysis based on the coupled mode theory and the Fabry-Perot resonance theory. The developed Dirac semimetal plasmonic structures pave the way to the development of novel THz active devices for light modulation platform.