Rough Quasi‐Conformal Mapping for Realizing Omnidirectional Light Wave Manipulation in Lower‐Index Meta‐Lens

Abstract Transformation optics is crucial for realizing low‐profile lenses with exceptional wave‐bending capabilities. However, conventional designs result in highly anisotropic and non‐uniform refractive indices, complicating practical implementation. Although quasi‐conformal methods mitigate anisotropy, the transformed index remains excessively large, posing challenges for terahertz material selection. This article introduces a different transformation strategy that sacrifices local angle preservation, reducing the maximum index to a commercially available material level. Besides, a semicircular meta‐lens capable of near‐omnidirectional plane wave focusing, with a maximum index of only 2.86, is demonstrated based on the proposed strategy. The work offers a general and practical solution for achieving low‐profile, low‐index, and high‐performance transformation lenses, which can be extended to millimeter‐wave and visible light.