Flat band meta-optics for compact photodiodes

Sub-wavelength structuring of semiconductors has recently provided a powerful tool to engineer the dispersion of the light. Such structures, commonly known as meta-optics can achieve a non-trivial relation between the energy and momentum of photons. One particular possibility is to create a dispersion-free flat band, which allows a resonator to maintain the same resonance frequency for different incidence angles. In this work, we utilize a flat band meta-optic to create a photodiode which has a critically coupled absorption for a wide angular range (±18°). By implementing a lens-based concentrator, the size of the photodiode can remain small while collecting large amounts of light, which results in high resolution, low energy consumption, and fast operation speed of the photodiode.