Terahertz broadband beam-steering Dirac semimetal-coding metasurface based on a genetic algorithm.

In this paper, a reflective terahertz broadband coding metasurface based on a genetic algorithm using Dirac semimetals as tunable materials is presented, which can realize flexible control of beam steering in the frequency range of 1.49-1.63 THz. First, the three-layer coding metasurface unit with the top layer of the Dirac semimetal pattern is designed using the electrically tunable dielectric constant of Dirac semimetals, which is capable of 2-bit coding in the frequency range of 1.49-1.63 THz. Then, the array arrangements of the coding metasurface are reverse-designed using a genetic algorithm. The results show that not only can both single- and multi-beams be realized at continuous arbitrary angles in the range of an elevation angle of 30° and an azimuth angle of 360°, but also the elevation angle and azimuth angle of each beam in the multi-beam can be controlled independently, which improves the flexibility of terahertz beam steering. Moreover, the steering range of the single-beam elevation angle is further expanded to 39° by employing the Fourier convolution addition rule. Therefore, the proposed terahertz broadband beam-steering Dirac semimetal-coding metasurface has certain application prospects in the fields of terahertz broadband communications and antennas.