Imaging with an Ultrathin Reciprocal Lens

• Published in: Physical review. X 2023-09, Vol.13 (3), p.031039, Article 031039
• Main Authors: Liu, Wenzhe, Chen, Jingguang, Li, Tongyu, Zhang, Zhe, Guan, Fang, Shi, Lei, Zi, Jian, Chan, C. T.
• Format: Article
• Language: English
• ISSN: 2160-3308; 2160-3308
• DOI: 10.1103/PhysRevX.13.031039

Imaging is of great importance in everyday life and various fields of science and technology. Conventional imaging is achieved by bending light rays originating from an object with a lens. Such ray bending requires space-variant structures, inevitably introducing a geometric center to the lens. To overcome the limitations arising from the conventional imaging mechanism, we consider imaging elements that employ a different mechanism, which we call reciprocal lenses. This type of imaging element relies on lateral ray shifting, enabled by momentum-space-variant phase modulations in periodic structures. As such, it has the distinct advantage of not requiring alignment with a geometric center. Moreover, upright real images can be produced directly with a single reciprocal lens as the directions of rays are not changed. We realize an ultrathin reciprocal lens based on a photonic crystal slab. We characterize the lateral ray shifting behavior of the reciprocal lens and demonstrate imaging. Our work gives an alternative mechanism for imaging and provides a new way to modulate electromagnetic waves.