Brewster Lens With Perfect Wave Refraction

A unified Brewster effect condition is proposed as a guideline for the design of the reflectionless lens. Previously, most of the investigations on the Brewster effect are limited for the homogeneous isotropic medium and the condition is sensitive to the polarization states. Here, it is predicted both theoretically and numerically that an arbitrarily polarized electromagnetic wave can perfectly refract through an anisotropic plate. In particular, both TE- and TM-polarized incident waves can have an identical Brewster angle with total transmission at either normal or oblique incidence by adjusting the material anisotropy. As a proof of concept, we employ this unified theory into the design of a 2-D reflectionless lens with a simplified restriction condition. It is demonstrated that perfect wavefront shaping with no fundamental limits on its efficiency is obtained with the proposed topology. To illustrate practically the concept of Brewster lens, a three-layer cascaded lens is fabricated and measured with a thickness of 0.1λ and an aperture efficiency of 94.3%. A remarkable 10.3 dB gain increasement is obtained compared with its counterparts.