Giant All-Optical Modulation of Second-Harmonic Generation Mediated by Dark Excitons


Wang Y., Das S., Iyikanat F., Dai Y., Li S., Guo X., ...More

ACS Photonics, vol.8, no.8, pp.2320-2328, 2021 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 8 Issue: 8
  • Publication Date: 2021
  • Doi Number: 10.1021/acsphotonics.1c00466
  • Journal Name: ACS Photonics
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Compendex, INSPEC
  • Page Numbers: pp.2320-2328
  • Keywords: Second-Harmonic Generation, Dark Excitons, Bright Excitons, Transition Metal Dichalcogenides Monolayers, Ultrafast Optical Modulation, Optically-Modulated Excitonic Strength
  • Dokuz Eylül University Affiliated: No

Abstract

All-optical control of nonlinear photonic processes in nanomaterials is of significant interest from a fundamental viewpoint and with regard to applications ranging from ultrafast data processing to spectroscopy and quantum technology. However, these applications rely on a high degree of control over the nonlinear response, which still remains elusive. Here, we demonstrate giant and broadband all-optical ultrafast modulation of second-harmonic generation (SHG) in monolayer transition-metal dichalcogenides mediated by the modified excitonic oscillation strength produced upon optical pumping. We reveal a dominant role of dark excitons to enhance SHG by up to a factor of ∼386 at room temperature, 2 orders of magnitude larger than the current state-of-the-art all-optical modulation results. The amplitude and sign of the observed SHG modulation can be adjusted over a broad spectral range spanning a few electronvolts with ultrafast response down to the sub-picosecond scale via different carrier dynamics. Our results not only introduce an efficient method to study intriguing exciton dynamics, but also reveal a new mechanism involving dark excitons to regulate all-optical nonlinear photonics.