Mid-infrared light is ideal for a number of practical applications, including night vision, chemical fingerprinting, and imaging or communication through scattering media. However, few practical techniques currently allow for active control of mid-infrared light beams. In the technology reported here, large amplitude, phase, and/or polarization modulation of infrared light can be achieved by electrically-tunable, metallic plasmonic antennas loaded with graphene. These antennas can dynamically modulate infrared light intensity with an on-off extinction ratio over 20 dB and phase over an extensive range with favorable modulation rate. Ultra-thin, flat optical components made of a two-dimensional array of such antennas can dynamically mold optical wavefronts into arbitrary shapes with fast speed. This has major implications for beam steering devices and spatial light modulators.
Plasmonic antenna resonance is reached when incident light waves match the natural frequency of collective electron oscillations in the antenna. The amplitude, phase and polarization of light scattered from the antenna can be largely modulated by adjusting the antenna's local environment, thus shifting its resonance. In this technology, graphene is used as the active medium to shift the optical resonance of metallic antennas due to graphene's highly tunable optical conductivity in the mid-infrared spectral range. Plasmonic antennas help mediate a very strong interaction between infrared light and thin graphene sheets, enabling large tuning of the optical properties of the graphene-metal plasmonic antennas. Modulation is instantaneous via optical scattering. These flat, lightweight optical devices can be built by using conventional planar micro- and nano-fabrication techniques.
The inventors provide firm evidence of graphene's tunability and graphene-metal antennas' light-modulation capabilities via finite-difference time-domain simulations and proof of principle experiments.
Tech Ventures Reference: IR CU13186
