Imaging with an ultra-thin reciprocal lens

TL;DR

This paper introduces an ultra-thin reciprocal lens that uses momentum-space-variant phase modulations to achieve imaging without traditional ray bending, enabling simpler, alignment-free imaging with potential for advanced wave modulation.

Contribution

The work presents the first realization of an ultra-thin reciprocal lens based on a photonic crystal slab, demonstrating a novel imaging mechanism that does not require geometric center alignment.

Findings

Successfully demonstrated imaging with the reciprocal lens

Characterized the ray shifting behavior of the lens

Showed direct production of upright real images

Abstract

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 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 realized an ultra-thin reciprocal lens based on a photonic crystal slab. We characterized the ray shifting behavior of the reciprocal lens and demonstrated imaging. Our work gives an alternative mechanism for imaging, and provides a new way to modulate electromagnetic waves.