Experimental Demonstration of Ultrafast THz Modulation in a Graphene-Based Thin Film Absorber through Negative Photoinduced Conductivity

Anna C. Tasolamprou, Anastasios D. Koulouklidis, Christina Daskalaki, Charalampos P. Mavidis, George Kenanakis, George Deligeorgis, Zacharias Viskadourakis, Polina Kuzhir, Stylianos Tzortzakis, Maria Kafesaki, Eleftherios N. Economou, Costas M. Soukoulis

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16 Citations (Scopus)

Abstract

We present an experimental demonstration and interpretation of an ultrafast optically tunable, graphene-based thin film absorption modulator for operation in the THz regime. The graphene-based component consists of a uniform CVD-grown graphene sheet stacked on an SU-8 dielectric substrate that is grounded by a metallic ground plate. The structure shows enhanced absorption originating from constructive interference of the impinging and reflected waves at the absorbing graphene sheet. The modulation of this absorption, which is demonstrated via a THz time-domain spectroscopy setup, is achieved by applying an optical pump signal, which modifies the conductivity of the graphene sheet. We report an ultrafast (on the order of few ps) absorption modulation on the order of 40% upon photoexcitation. Our results provide evidence that the optical pump excitation results in the degradation of the graphene THz conductivity, which is connected with the generation of hot carriers, the increase of the electronic temperature, and the dominant increase of the scattering rate over the carrier concentration as found in highly doped samples.

Original languageEnglish
JournalACS Photonics
DOIs
Publication statusPublished - 1 Jan 2019

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Keywords

  • experimental grapheme absorber
  • flat optics modulation
  • grapheme photoexcitation
  • hot carrier generation
  • THz graphene
  • ultrafast THz tunable grapheme metasurface

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biotechnology
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering

Cite this

Tasolamprou, A. C., Koulouklidis, A. D., Daskalaki, C., Mavidis, C. P., Kenanakis, G., Deligeorgis, G., Viskadourakis, Z., Kuzhir, P., Tzortzakis, S., Kafesaki, M., Economou, E. N., & Soukoulis, C. M. (2019). Experimental Demonstration of Ultrafast THz Modulation in a Graphene-Based Thin Film Absorber through Negative Photoinduced Conductivity. ACS Photonics. https://doi.org/10.1021/acsphotonics.8b01595