Tuneable infrared perfect absorber based on spatially separated double-layer graphene

Graphene plasmons are widely used for light trapping and absorption engineering in optoelectronic devices. They are less lossy than the plasmons of conventional materials like gold and silver and can be tuned by electrostatic or chemical doping. We use a theoretical model to numerically demonstrate a novel absorber based on spatially separated double-layer graphene that can achieve perfect absorption and is electrically tuneable in the infrared range. Electrodes are placed on the upper and lower graphene sheets, and the depth of the dielectric between them is sufficiently low to achieve a high Fermi level with a low bias voltage. This absorber facilitates the tuning of the Fermi level compared to graphene nanoribbons/disks and does not require periodic dielectric/metal arrays to excite the plasmons. When the resonant wavelength is 10 μm, the total thickness of the device is less than 2 μm, and the required bias voltage is low. Therefore, the absorber has promising applications in infrared photodetectors, sources, and other photodevices that will benefit from these device integration and miniaturization advantages and require absorption enhancement.