Plasmonic Metasurface CFA for SPAD Imager

OSA Optica publishes a paper "Ultralow-light-level color image reconstruction using high-efficiency plasmonic metasurface mosaic filters" by Yash D. Shah, Peter W. R. Connolly, James P. Grant, Danni Hao, Claudio Accarino, Ximing Ren, Mitchell Kenney, Valerio Annese, Kirsty G. Rew, Zoë M. Greener, Yoann Altmann, Daniele Faccio, Gerald S. Buller, and David R. S. Cumming from Glasgow University, Heriot-Watt University, UK and Boise State University, USA.

"We have fabricated a high-transmittance mosaic filter array, where each optical filter was composed of a plasmonic metasurface fabricated in a single lithographic step. This plasmonic metasurface design utilized an array of elliptical and circular nanoholes, which produced enhanced optical coupling between multiple plasmonic interactions. The resulting metasurfaces produced narrow bandpass filters for blue, green, and red light with peak transmission efficiencies of 79%, 75%, and 68%, respectively. After the three metasurface filter designs were arranged in a 64×64 format random mosaic pattern, this mosaic filter was directly integrated onto a CMOS single-photon avalanche diode detector array. Color images were then reconstructed at light levels as low as approximately 5 photons per pixel, on average, via the simultaneous acquisition of low-photon multispectral data using both three-color active laser illumination and a broadband white-light illumination source."