Spaceplates: The Final Frontier in Compressing Optical Systems

Abstract

In the last decade, metalenses have become an increasingly popular topic of research, partly due to their ability to reduce the physical space that would otherwise by occupied by traditional lenses, thereby reducing the length of the optical system. However, metalenses do not reduce the largest contributor to optical system length: the propagation of the light between optical elements. We present a novel optic, which we call a “spaceplate,” that can replicate propagation distance of light greater than its thickness, without changing the magnification. We demonstrate the capabilities of spaceplates via proof of concept experiments that use two distinct types of spaceplate; the “low-index” spaceplate is based on Snell’s Law, while the “uniaxial” spaceplate utilizes the anisotropy of birefringent crystals. The 11 mm thick low-index spaceplate reduced light propagation by (4.7 ± 0.2) mm and the 15 mm thick uniaxial spaceplate reduced light propagation by (1.2 ± 0.2) mm. Future spaceplates, especially in conjunction with metalenses, could vastly decrease the length of optical systems, including imaging systems like cameras, and has the potential to make such systems monolithic.