Experimental demonstration of high space compression by optical spaceplates

The large physical size of optical imaging systems is one of the greatest constraints on their use, limiting the performance and deployment of a range of systems from telescopes to mobile phone cameras. Spaceplates are nonlocal optical devices that compress free-space propagation into a shorter distance, paving the way for more compact optical systems, potentially even thin flat cameras. Here, we demonstrate an engineered optical spaceplate and experimentally observe the highest space compression ratios yet demonstrated in any wavelength region, up to $R=176\pm 14$ , which is 29 times higher than any previous device. Our spaceplate is a multilayer stack, a well-established commercial fabrication technology that supports mass production. The versatility of these stacks allows customization of the spaceplate's bandwidth and angular range, impossible with previous optical experimental spaceplates made of bulk materials. With the appropriate choice of these two parameters, multilayer spaceplates have near-term applications in light detection and ranging (LIDAR) technologies, retinal scanners, endoscopes, and other size-constrained optical devices.