Fig. 1. Lenses used in a THz communication system. (a) Conventional THz lens made by Teflon; (b) 3D printed THz multilevel lens.

Fig. 2. Design, optimization, fabrication, and characterization process of 3D-printed THz multilevel diffractive lens. (a) Optimization flow; (b) multilevel lens profile designed using theoretical calculation; (c) 3D printer (RAISE3D N2) was used in the fabrication. (d) The multilevel diffractive lens is fabricated using 3D printing technology. (e) Configuration for focusing characterization experiments. PSO, particle swarm optimization; DE, differential evolution; GD, gradient descent.

Fig. 3. Simulation and experiment results of THz lenses. (a), (b) Structures of the 6-level lens and 21-level lens, respectively; (c), (d) simulation results of the 6-level lens and 21-level lens, respectively; (e), (f) experiment results of the 6-level lens and 21-level lens, respectively; (g) BER tested through the THz communication system, comparing the performance of Teflon and two different multilevel 3D printed PLA lens; (h) picture of the THz communication system used; (i), (j) eye contour of the THz communication system using Teflon and 21-level 3D printed PLA lens, respectively.

Fig. 4. Simulation and experiment results of high NA THz lens. (a) Structure of high NA THz multilevel lens; (b) power distribution of the lens on the x–y plane and r–z plane; (c) experiment results of multilevel lens received around focal length; (d), (e) illustration of simulation and experiment results along the r coordinate and z coordinate, respectively.

Fig. 5. Simulation results of THz chromatic and achromatic multilevel lens. (a), (b) Simulation results ranging from 0.11 to 0.17 THz of the chromatic and achromatic lens, respectively; (c) structure of the achromatic lens optimized; (d), (e) simulation results ranging from 0.11 to 0.17 THz on z coordinate of both chromatic and achromatic lens, respectively.