Terahertz Surface Plasmon Refractometry of Composite Graphene Nanoparticle Films

Graphene is one of the most promising materials for terahertz (THz) plasmonics. Composite layers composed of graphene nanoparticles are easier to fabricate, and their composition variability allows for the customization of desired optical surface characteristics. This study is the first to apply THz surface plasmon refractometry methods to investigate composite films of graphene nanoparticles (with poly-34-ethylenedioxythiophene/ polystyrene sulfonate additive) with thicknesses of 35 and 400 nm. The Novosibirsk free-electron laser, generating monochromatic wavelength-tunable coherent radiation, was used as a THz radiation source. The measurement of the effective dielectric permittivity of the layers at wavelengths of 141 and 197 μm indicated their good conductive properties. Results of the comparison of permittivity for different thicknesses of graphene layers have revealed a complex mechanism of conductivity of the composite material, which differs significantly from the Drude model estimations. So, further thorough experimental research of this material is required. The main results suggest the potential application of composite graphene films hundreds of nanometers thick in plasmonic integrated circuits and THz frequency range communication lines.