Mid-infrared pyroelectric detector with metasurface electrode for broadband enhanced absorption

Abstract

Pyroelectric photodetectors have continuously been an attractive candidate due to their noncryogenic and easy-to-fabricate specifics. Because the detectivity or resolution of the pyroelectric detector is closely related to the absorptivity to incident radiation, we propose a scheme for a metasurface-based pyroelectric detector (MPPD) by constructing its top electrode with an absorptive metasurface composed of nanogrid-patch units. The resonance modes of Fabry–Perot cavity, magnetic dipole and electric dipole are collectively leveraged for the mid-infrared MPPD with optimal broadband absorption plus three absorptive peaks at 3.13 μm, 3.94 μm and 4.8 μm. The mechanisms and field distributions of these resonance peaks are intensively explored and verified for configuration of the metasurface top electrode with optimized geometries. Finally, our scheme achieves an average absorptivity of 94.2% in the mid-infrared range of 3–5 μm, with its thermal response enhanced by 2.6 times that results in a significantly improved pyroelectric current for the detector.