Abstract
As single-photon imaging becomes progressively more commonplace in sensing applications such as low-light-level imaging, three-dimensional profiling, and fluorescence imaging, there exist a number of fields where multispectral information can also be exploited, e.g., in environmental monitoring and target identification. 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.
Highlights
Single-photon imaging is a rapidly expanding field of research with emerging applications in three-dimensional profiling [1], kilometer-range depth profiling [2], three-dimensional imaging of moving targets [3], astrophysics [4], and fluorescence lifetime imaging (FLIM) [5]
A closer analysis of the design reveals that destructive interference between quasi-cylindrical waves (QCWs) [56,57,58,59] and surface plasmon polaritons (SPPs) oscillating on the surface produces a dip in transmission, aiding out-of-band rejection, while a high transmission is observed due to constructive coupling between the QCW, SPPs, and localized surface plasmon resonance (LSPR)
We have demonstrated plasmonic metasurface wavelength filters comprising nanocircles and nanoellipses that achieve ultrahigh transmission efficiency for blue, green, and red light by simultaneously enhancing three optical phenomena: LSPR, SPPs, and QCWs
Summary
Single-photon imaging is a rapidly expanding field of research with emerging applications in three-dimensional profiling [1], kilometer-range depth profiling [2], three-dimensional imaging of moving targets [3], astrophysics [4], and fluorescence lifetime imaging (FLIM) [5]. Plasmonic metasurfaces [20] have gained prominence in this field due to their ability to simultaneously, and individually, control the phase [21,22,23,24], momentum [25], amplitude [26], optical nonlinearities [24,27,28], wavefront steering [29,30], and polarization [23,31] of light Such plasmonic metasurfaces have considerable utility in the realization of compact photonic devices [32]— fabricated by exploiting tunable resonant properties controlled by near-field coupling [33]. Polarization insensitivity with 60% transmission has been achieved using circular nanoholes [52] in a metal–insulator–metal configuration, but this design required a complex, multistage fabrication approach and had large out-of-band transmission (poor rejection ratios)
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