title: Electrically tunable metasurface perfect absorbers for ultrathin mid-infrared optical modulators.
abstract: Dynamically reconfigurable metasurfaces open up unprecedented opportunities in applications such as high capacity communications, dynamic beam shaping, hyperspectral imaging, and adaptive optics. The realization of high performance metasurface-based devices remains a great challenge due to very limited tuning ranges and modulation depths. Here we show that a widely tunable metasurface composed of optical antennas on graphene can be incorporated into a subwavelength-thick optical cavity to create an electrically tunable perfect absorber. By switching the absorber in and out of the critical coupling condition via the gate voltage applied on graphene, a modulation depth of up to 100% can be achieved. In particular, we demonstrated ultrathin (thickness < λ0/10) high speed (up to 20 GHz) optical modulators over a broad wavelength range (5-7 μm). The operating wavelength can be scaled from the near-infrared to the terahertz by simply tailoring the metasurface and cavity dimensions.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Yu
authors.initials: Y
authors.lastname: Yao
authors.forename: Raji
authors.initials: R
authors.lastname: Shankar
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Kats
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.forename: Jing
authors.initials: J
authors.lastname: Kong
authors.forename: Marko
authors.initials: M
authors.lastname: Loncar
authors.forename: Federico
authors.initials: F
authors.lastname: Capasso
mesh_terms: D004560:Electricity; D004581:Electronics / Q000295:instrumentation*; D004867:Equipment Design; D006108:Graphite / Q000737:chemistry*; D007259:Infrared Rays; D055095:Optics and Photonics / Q000295:instrumentation*
chemical_list: D006108:Graphite
keywords: Metasurface perfect absorbers; electrically tunable; graphene; mid-infrared optoelectronics; optical modulators