Meta-optic Spectropolarimeter For Heliophysics Imaging

Spectropolarimetric measurements show great promise for heliophysics in many wavelength regimes, including for observing hydrogen-alpha (H-alpha) emissions in solar flares, or UV features of the K-corona. Recently, under NASA contract 80NSSC22CA172, Nanohmics and Professor Andrea Alù’s research group at the City University of New York (CUNY) demonstrated the potential of multifunction meta-optics that can focus light and can also analyze both spectrum and polarization state for light in the deep red, NIR, and SWIR. To adapt this metamaterial technology to H-alpha and other visible (VIS) spectral bands used for heliophysics missions, Nanohmics proposes to develop a VIS band, low-SWaP imaging spectropolarimeter using an ultrathin, light-weight, microfabricated multifunction meta-optic. The proposed imaging spectropolarimeter combines a single multifunction meta-optic with a commercial off-the-shelf (COTS) focal plane array (FPA). It will collect polarization, spectral, and one-dimensional (1D) imaging data simultaneously at video rates and hyperspectral resolution. Its mass and volume will be approximately 1/10 of that of existing spectropolarimeters. The core metamaterial-based optic performs polarization, wavelength, and spatial discrimination with no moving parts. In Phase I, the team will demonstrate the feasibility of low-SWaP, high-performance heliophysics-suited sensors by fabricating a brassboard imaging spectropolarimeter using a single multifunction meta-optic. Laboratory testing will advance the brassboard to TRL 4. In Phase II, the team will advance the brassboard to the prototype stage (TRL 5) through ruggedization and testing. Longer term, the proposed technology can be integrated into NASA heliophysics missions, e.g., CubeSats and other SWaP-constrained vehicles. Meta-optic fabrication using standard CMOS microfabrication techniques will reduce costs and provide a rapid route to commercialization.
Benefits: By providing imaging, polarimetry, and spectroscopy in a compact low-cost package, the proposed sensor is ideal for measurements on heliophysics missions – initially in red wavelengths to investigate H-alpha, but extensible to cover other VIS spectral bands. Combining polarization and spectral data will enable detailed investigation of regions of the chromosphere, including imaging across flare origin and reconnection spots along the solar limb. Inspiration for this project is to improve upon measurements from the solar Zurich IMaging POLarimeter (ZIMPOL) instrument, which measured spectrum and polarization across VIS bands of the solar spectrum, viewing the solar limb. With the addition of positional imaging, the spectropolarimeter will provide an understanding of the chromosphere’s polarization features, particularly solar flare kernels. Spectropolarimeter operation centered on the H-alpha line (656 nm) is a first step toward other VIS sub-bands, given its prominence in astrophysics as a consistent emission line across stars and gas clouds; a strong and reliable indicator. Subsequent advances through VIS will enable further spectropolarimetric studies of particle acceleration processes. The spectropolarimeter can also advance into the ultraviolet (UV) to study the K-corona layer and the Lyman-alpha band, to better understand magnetic field topography and reconnection points. Longer term, the team proposes integration of the multi-band imaging spectropolarimeter and multifunction meta-optic technologies into a range of instruments for NASA heliophysics missions, including CubeSats and other SWaP-constrained vehicle payloads. The advanced capabilities and low SWaP of meta-optics sensors will make them valuable for many applications in the petroleum, chemical, pharmaceutical, electric power, and microelectronics sectors. These commercial applications may include defense; security; vehicle autonomy; agriculture; food processing, oceanography; water resource monitoring; waste management, water treatment; monitoring of terrestrial sources of industrial gas emissions; emissions compliance control for refineries and factories; and intelligence, surveillance, and reconnaissance (ISR) for the Department of Defense (DoD) and Homeland Security (DHS). Low-cost, low-SWaP spectropolarimeters can be installed throughout these facilities and/or carried by UASs or SmallSats to collect data that can be used to increase safety, efficiency, and environmental compliance. Nanohmics intends to aggressively commercialize the low-SWaP spectropolarimeter and its component multifunction meta-optic technology, as it has done with other optical and imaging innovations. The single meta-optic, microfabricated using standard CMOS processes, performs the function of multiple conventional optical elements, reducing complexity and production cost while increasing robustness and space-readiness.