Phase and Polarization Imaging Meta-Sensor Arrays

Nontechnical description: Optical image sensors are a foundational technology used in countless scientific, industrial, military, and consumer-product applications. Traditionally, the operation of these devices is limited to the measurement of the optical intensity incident on their illumination window. Light, however, possesses multiple other degrees of freedom besides intensity, including local direction of propagation (related to phase gradient) and polarization, that also contain important information of interest but generally require extremely complex and bulky systems for their detection. The proposed research will address this limitation by developing a new type of image sensor arrays that can directly measure, in a single shot and with standard imaging optics, the spatial distribution of the incident optical intensity, phase, and polarization. These systems could dramatically increase our ability to visualize objects under conditions of limited intensity contrast and to extract maximum information from the resulting images, especially in situations where miniaturization and speed are paramount. Thus, they could have a broad enabling impact on multiple applications of machine vision, ranging from biomedical microscopy and endoscopy to remote sensing and autonomous navigation. The proposed activities will also promote multidisciplinary training of a skilled workforce in nanophotonics, semiconductor nanofabrication, and image sensing technologies. Technical description: The proposed devices consist of standard silicon photodetectors coated with specially designed dielectric metasurfaces that introduce a sharp dependence of responsivity on illumination angle and polarization at visible wavelengths. The work plan will focus on the design, fabrication, and characterization of these metasurfaces, their integration within commercial CMOS sensor arrays, and the development of specialized computational protocols for image reconstruction with these systems. Two different super-pixel configurations will be demonstrated: (1) a phase-imaging meta-sensor (PIMS) array capable of single-shot quantitative phase reconstruction; and (2) a phase- and polarization-imaging meta-sensor (P2IMS) array providing the additional capability of full-Stokes polarimetry to allow for a complete measurement of the incident optical field. These activities will advance the science and technology of metasurfaces in a novel fashion, by exploring their direct integration within image sensor arrays to control the optical response of individual devices on a pixel-by-pixel basis. At the same time, this project will also promote new developments in computational imaging by merging reconstruction protocols that are traditionally used for quantitative phase imaging with full-Stokes polarimetry. The proposed image sensors are also compatible with wafer-scale manufacturing in a CMOS foundry, which adds to their promise for a widespread technological impact in the broad field of machine vision. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.