3-D Printed Terahertz Planar Edge Focal Symmetric GRIN Lens With Planar Focal Surface for Enhanced Beam-Steering Based on Ray Optics

A terahertz planar gradient-refractive-index (GRIN) lens with wide-angle beam-steering is designed in this work. By calculating the relative permittivity (ϵ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub>) distribution of an edge focal lens and then applying symmetry, a novel edge focal symmetric GRIN lens with wide-angle scanning capability is realized. By studying parameters such as the lens thickness, focal length, relative permittivity at the focal point, and the output angle, a relative permittivity distribution has been obtained that can significantly enhance the scanning performance of the lens. The proposed lens is capable of achieving good scanning performance and supporting dual-polarization functionality with a planar feed. The proposed lens is fabricated using high-precision 3D printing technology to validate the designed gradient-index distribution. A lens was designed to validate the proposed design approach and measured at a frequency of 220 GHz. The results demonstrate that the proposed lens, featuring a planar focal surface, achieves a wide beam scanning range of ±41° in vertical polarization and ±39° in horizontal polarization. Moreover, the lens has a maximum aperture efficiency of 39.86%.