Probing the origin of highly-efficient third-harmonic generation in plasmonic nanogaps

Published

Journal Article

© 2018 Optical Society of America. Plasmonic structures can precisely localize electromagnetic energy to deep subwavelength regions resulting in significant field enhancement useful for efficient on-chip nonlinear generation. However, the origin of large nonlinear enhancements observed in plasmonic nanogap structures consisting of both dielectrics and metals is not fully understood. For the first time, here we probe the third harmonic generation (THG) from a variety of dielectric materials embedded in a nanogap plasmonic cavity. From comprehensive spectral analysis of the THG signal, we conclude that the nonlinear response results primarily from the dielectric spacer layer itself as opposed to the surrounding metal. We achieved a maximum enhancement factor of more than six orders of magnitude compared to a bare gold film, which represents a nonlinear conversion efficiency of 8.78 × 10−4%. We expect this new insight into the nonlinear response in ultrathin gaps between metals to be promising for on-chip nonlinear devices such as ultrafast optical switching and entangled photon sources.

Full Text

Duke Authors

Cited Authors

  • Shen, Q; Hoang, TB; Yang, G; Wheeler, VD; Mikkelsen, MH

Published Date

  • August 6, 2018

Published In

Volume / Issue

  • 26 / 16

Start / End Page

  • 20718 - 20725

Electronic International Standard Serial Number (EISSN)

  • 1094-4087

Digital Object Identifier (DOI)

  • 10.1364/OE.26.020718

Citation Source

  • Scopus