Metasurface folded lens system for ultrathin cameras.

Slim cameras are essential in state-of-the-art consumer electronics such as smartphones or augmented/virtual reality devices. However, reducing the camera thickness faces challenges primarily due to the thick lens systems. Current lens systems, composed of stacked refractive lenses, are fundamentally constrained from becoming thinner due to the presence of empty spaces between lenses and the excessive volume of each lens. Here, we present a lens system using metasurface folded optics to overcome these pervasive issues. In our design, metasurfaces are arranged horizontally on a glass wafer and direct light along multifolded paths inside the substrate. This approach achieves an ultra-slim lens system with a thickness of 0.7 millimeters and 2× thinner relative to the EFL, thereby overcoming the inherent limitations of conventional optical platforms. It delivers quasi-diffraction-limited imaging quality with a 10° field of view and an number of 4 at an operational wavelength of 852 nanometers. Our findings provide a compelling platform for compact cameras using folded nano-optics.