Used in optical computing and computational imaging, diffractive optical processors and metasurfaces are flourishing within the computing industry. The demonstrations of these materials are constrained to 2D implementations and longer wavelengths due to the fabrication challenges of nanoscale features in 3D diffractive architectures. Researchers at the UCLA Samueli School of Engineering and the Optical Systems Division at Broadcom Inc. have developed a broadband, polarization-insensitive unidirectional imager that operates in the visible spectrum, capable of high-efficiency image transmission in one direction while effectively suppressing image formation in the reverse direction. This device incorporates diffractive structures fabricated through wafer-scale lithography on high-purity fused silica, offering high optical transparency, thermal stability, and ultra-low loss. The researchers demonstrated that their nano-fabrication approach, along with deep learning-based inverse design, enables visible image formation in only one direction, transmitting images from the input field of view to the output field of view — while blocking and distorting image formation in the reverse direction. According to the researchers, the work represents the first demonstration of broadband unidirectional imaging in the visible spectrum, achieved with nanoscale, polarization-insensitive diffractive features that were optimized using deep learning. The developed fabrication process leverages methods compatible with semiconductor manufacturing, opening the potential to optoelectronic components. This work marks significant advancement towards future advances in computational imaging, optical sensing, and optical information processing, with potential applications in compact multispectral imagers and optical privacy protection. This research was published in Light Science & Applications (www.doi.org/10.1038/s41377-025-01971-2).
