Metalenses are essential components in terahertz imaging systems. However, without careful design, they show limited field of view and their practical applications are hindered. Here, a wide-angle metalens is proposed whose structure is optimized for focusing within the incident angles of ±25°. Simulation and experiment results show that the focusing efficiency, spot size, and modulation transfer function of this lens are not sensitive to the incident angle. More importantly, this wide-angle metalens follows the ideal Gaussian formula for the object-image relation, which ensures a wider field of view and better contrast in the imaging experiment.

Terahertz (THz) lenses have numerous applications in imaging and communication systems. Currently, the common THz lenses are still based on the traditional design of a circular convex lens. In this work, we present a method for the design of a 3D-printed multilevel THz lens, taking advantage of the benefits offered by 3D printing technology, including compact size, lightweight construction, and cost-effectiveness. The approach utilizes an inverse design methodology, employing optimization methods to promise accurate performance. To reduce simulation time, we employ the finite-difference time-domain method in cylindrical coordinates for near-field computation and couple it with the Rayleigh–Sommerfeld diffraction theory to address far-field calculations. This technology holds great potential for various applications in the field of THz imaging, sensing, and communications, offering a novel approach to the design and development of functional devices operating in the THz frequency range.