Graphene-based optical antennae for achieving an ultra-broad infrared radiation absorption and further guiding a spectral fluorescent conversion

We present a graphene-based optical antenna with a layered configuration. The basic structure is formed by orderly stacking the 10-, 20-, and 30-layer single-crystal graphene sheets on a common Cu substrate, where each adjacent graphene layer is strictly separated by a Si3N4 film. An average infrared (IR) radiation absorptivity of ~86.1% in an ultra-broad wavelength region of 1-25μm can be realized. Both the IR absorptivity of ~88.54% and a reflectivity variance of ~23.09% in a wide waveband of 1-15μm by directly applying a bias voltage varied in a range of 0-20V, are achieved. The ideal broadband IR absorption and its electrically adjusting characteristics can be attributed to an enhanced Fabry-Pérot resonance and the optimized impedance matching. The established graphene-based optical antenna is also utilized to guide a spectral conversion from an initial near-IR radiation with a central wavelength of 2.2μm and also a red beam with a central wavelength of 655 nm into the visible fluorescent irradiation with a central wavelength of 544nm. The measured pc-to-dc ratio through a graphene-based fluorescent conversion sensing module (GFCSM) constructed by directly coupling the graphene-based optical antenna with a conventional microchannel plate (MCP) and a fluorescent screen, is ~13.78 and ~31.13, respectively.