Designing high-performance propagation-compressing spaceplates using thin-film multilayer stacks

TL;DR

This paper uses inverse-design methods to develop thin-film multilayer spaceplates that significantly miniaturize optical systems by compressing space with high efficiency, demonstrating record compression ratios with simple material stacks.

Contribution

It introduces a systematic inverse-design approach to optimize thin-film multilayer spaceplates, achieving high compression ratios and broadening practical applications.

Findings

Achieved a compression factor of R=5.5 at NA=0.42

Reached a record compression factor of R=340 at NA=0.017

Simple silicon and glass multilayer stacks can effectively function as spaceplates

Abstract

The development of metasurfaces has enabled unprecedented portability and functionality in flat optical devices. Spaceplates have recently been introduced as a complementary element to reduce the space between individual metalenses. This will further miniaturize entire imaging devices. However, a spaceplate necessitates a non-local optical response -- one which depends on the transverse spatial frequency component of a light field -- therefore making it challenging both to design them and to assess their ultimate performance and potential. Here, we employ inverse-design techniques to explore the behaviour of general thin-film-based spaceplates. We observe a tradeoff between the compression factor R and the numerical aperture NA of such devices; we obtained a compression factor of R = 5.5 for devices with an NA = 0.42 up to a record R = 340 with NA of 0.017. Our work illustrates that even simple designs consisting of realistic materials (i.e., silicon and glass) permit capable spaceplates for monochromatic applications.