Metasurface color filter arrays with a high efficiency and low color error

Conventional digital cameras combine absorbing color filter arrays with microlenses to achieve color imaging and improve efficiency. Such cameras require multi-step and multi-material fabrication processes. Several recent efforts have investigated metasurface-based color routing to combine focusing with filtering in a single functional layer with an improved efficiency. These approaches require high-refractive index materials and deep sub-micron fabrication to realize the metasurfaces. We present here an alternative, 2.5 dimensional metasurface that simultaneously provides both color filtering and focusing, but requires only a low-refractive index polymer and micron-scale patterning such that it is suitable for replication by molding. Unlike Bayer filters, this metasurface produces six independent spectra focused on nine monochrome pixels yielding both a high efficiency and low color error. These metasurfaces could be more photo-stable and thermally stable than dye-based filters and less expensive to produce than conventional arrays or metasurface color routers. Here, we characterize a metasurface-based focusing color filter array prototyped using two-photon lithography whose efficiencies are competitive with Bayer filters and whose color error is comparable to the limit of human perception.