Metasurfaces for Compact, Next-Generation Polarimetric Remote Sensing of Aerosols and Clouds

Aerosols – suspensions of solid or liquid droplets in air – present a unique challenge in atmospheric science and are, together with their interactions with clouds, key sources of uncertainty in global climate models. Light's polarization state upon scattering from aerosols and clouds is known to carry information that can aid in determination of their mean size, droplet size uniformity, shape, and absorption properties. However, the current instrumentation for polarimetry (the measurement of light's polarization state) is bulky and/or reliant on moving parts. Metasurfaces – subwavelength spaced arrays of nanophotonic phase shifters, an emergent optical technology – have recently been shown to implement polarization imaging with all polarization analysis handled by a single optical element and thus hold promise for a new class of polarization instrumentation for remote sensing. To date, no past, current, or planned Earth Science airborne/spaceborne polarimeter has measured light's circular polarization. Metasurfaces easily yield information on the circular polarization of light, therefore, the utility this seldom-measured quantity can have for aerosol and cloud remote sensing will be investigated. The proposed IIP-ICD effort will evaluate whether metasurface-based polarimetry can achieve the accuracy mandated for cutting-edge aerosol and cloud remote sensing applications by partnering resources and personnel from Harvard University, leaders in the development of metasurfaces for polarimetric imaging, with aerosol and cloud remote sensing expertise at NASA GSFC. Our team proposes to examine the scientific feasibility of metasurfaces in this realm, whose compactness (when paired with this requisite accuracy) could enable a compact, next-generation remote sensing platform for application onboard a CubeSat. As part of this project we will fabricate several metasurface polarization camera prototypes in three wavelength bands relevant for aerosol and cloud remote sensing (550, 670, and 870 nm), characterize their accuracy, and investigate future applications of metasurfaces in polarimetry, advancing the technology from TRL 2 at entry and TRL 4 upon exit. Finally, the proposed effort will explore the utility of using new metasurface enabled observations of circular polarization for Earth Science applications; maturation of the technology has the potential to be cross-cutting with the Planetary Science community, as chirality, a potential indicator of complex biological life, contributes to the circular polarization signal.

Increase scientific understanding of natural phenomena using remote sensing

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