Experimental demonstration of 3D printed terahertz polarization-insensitive flat devices based on low-index meta-gratings

Abstract

Dielectric meta-gratings have achieved tremendous success in realizing high-efficiency wavefront control in terahertz range. Here, several efficient, polarization-insensitive, low-cost devices are investigated numerically and experimentally. First, an anomalous deflector based on a low-index polymer acrylonitrile butadiene styrene meta-grating is designed and measured around 0.1 THz. By breaking the distance limitation between the fixed bars and bending the terahertz beam into the T-1 diffraction order through the optimization of quadrumer unit cell, the efficiencies for 37◦ deflection under normal excitation reach 67.1% (56.4%) with the S-(P-) polarized terahertz wave, which are in good agreement with the simulated 71.8% (63.7%). Next, with regard to the concept of bending light by the proposed meta-grating array, a method for designing a terahertz flat lens is proposed and experimentally demonstrated with long focal length and polarization insensitivity. The proposed flat lens can achieve the measured numerical aperture of 0.604 (collection angle of 37.2◦.) and focusing efficiency of 50.3% with normal incident of linear polarized terahertz wave at 0.1 THz. Also, a focal spot with the focusing distance of 65.9 mm is achieved. These designs can be manufactured by 3D printing at low cost, and provide promising applications in imaging, communication, information processing and materials science.