All-dielectric phonon-polariton nonlinear nanoantennas for terahertz-photonics.

Arregui Leon U., Rocco D., Carletti L., Peccianti M., Maci S., Della Valle G., De Angelis C.
  Lunedì 12/09   14:00 - 19:00   Aula D - Marianna Ciccone   II - Fisica della materia   Presentazione
The Terahertz (THz) spectrum offers the potential of a plethora of applications, ranging from imaging to wireless communications and THz-photonics. The latter framework would greatly benefit from the development of optical-to-THz wavelength converters. Exploiting Difference Frequency Generation in a nonlinear all-dielectric nanoantenna, we propose a compact solution to this problem. By means of a near-infrared pump beam (at $\omega_{1}$), the information signal in the optical domain (at $\omega_{2}$) is converted to the THz band (at $\omega_{3} = \omega_{2}-\omega_{1}$). We numerically reveal an efficiency of up to $2 \cdot$ 10^$-7 {W^{-1}}$ from a single AlGaAs nanopillar, 8 orders of magnitude higher than that obtained from plasmonic split-ring nanoresonators; such a high value can be ascribed to the large bulk $\chi^{(2)}$ of AlGaAs as well as to the presence of phononic resonances at the THz region. The approach is particularly suitable for launching surface waves when integrated in a THz metasurface platform, and paves the way to further engineer the nonlinear emission pattern.