Dynamically tunable Graded Index Photonic Crystal lens based on Dirac semimetal

In this paper, we design a graded-index photonic crystal based on Dirac semimetals and simulate the light propagation in the proposed structure using two-dimensional finite-difference time-domain method. The numerical results indicate that the designed GRIN PC has focusing capability for incident light at terahertz frequency range, and its focal distance can be tuned through changing the Fermi energy of the Dirac semimetal.