Plasmonic Enhancement of Light-Matter Interactions in Graphene for Long-Wavelength Infrared Detection at room temperature.

The detection of long-wavelength infrared photons at room temperature is challenging due to low photon energy. The uncooled microbolometers suffer from low sensitivity, slow response, and complex fabrication processes. The Mercury Cadmium Telluride detectors require cryogenic cooling and intricate low-yield readout integrated circuit hybridization. The colloidal quantum-dot based detectors are hindered by high dark current and inefficient carrier transport. In this work, we present uncooled LWIR detection scheme based on nanopatterned graphene. Pristine graphene absorbs only a fraction of incident light, specifically 2.3%. Initially, we focus on the enhancement of light absorption by introducing nanopatterns in the graphene sheet, which excites localized surface plasmons around the edges. These plasmons, partially hybridized with graphene phonons and surface phonons of neighboring materials, enable control and tuning of the absorption spectrum (3um-14um) by adjusting nanopattern size and distance in a hexagonal or square lattice structure. The localized surface plasmons and an optical cavity increase graphene absorption to 100%. Then we engineer a photodetector by creating an asymmetric environment in the graphene sheet, patterning one side of the active area and leaving the other side unpatterned to take an advantage of the Seebeck effect in graphene. Our proposed detector exhibits high responsivity (10^4 V/W), detectivity (~10^9 Jones), and fast time response.