Abstract: A pixel for an image sensor is disclosed that includes a photodiode, a thin-film layer and a reflective layer. The photodiode includes a first side and a second side that is opposite the first side, and receives incident light on the first side. The thin-film layer is formed on the first side of the photodiode and provides a unidirectional phase-shift to light passing from the photodiode to the thin-film layer. The thin-film layer has a refractive index that less than a refractive index of material forming the photodiode. The unidirectional phase-shift may be a unidirectional it phase shift at a target near-infrared light wavelength. The reflective layer is formed on the second side of the photodiode and reflects light passing from the photodiode to the reflective layer toward the first side of the photodiode. The reflective layer may be a thin-film layer, a Distributed Bragg Reflector layer, or a metal.

Abstract: A lens system having reduced physical size. The lens system includes multiple metalenses, lenses with metasurfaces, that integrate the lens and the free space and compress them into multiple layers of metasurfaces, significantly reducing the overall volume and weight of the imaging system while increasing its efficiency. The lens system also provides for tools that can accurately model 3D multilayer metasurfaces, carry out inverse design to find the optimal and fault-tolerant structure, fabricate the metasurfaces with multi-project wafer service, assemble them with a 3D-printed holder, and characterize the performance of the resulting ultra-compact imaging system.