Near-zero-index ultra-fast pulse characterization

Wallace Jaffray, Federico Belli, Enrico Giuseppe Carnemolla, Catalina Dobas, Mark Donald Mackenzie, John C. Travers, Ajoy Kumar Kar, Matteo Clerici, Clayton DeVault, Vladimir M. Shalaev, Alexandra Boltasseva, Marcello Ferrera

Research output: Contribution to journalArticlepeer-review

Abstract

Transparent Conducting Oxides (TCOs) are highly doped wide-bandgap materials whose Fermi-level sits into the conduction band, thus promoting both electric conductivity and optical transparency at the same time. Recently, it has been shown that TCOs exhibit giant optical nonlinearities in the near-infrared window where the linear index approaches zero. The nonlinear response of these materials is extremely high, pointing in the direction of transformative new photonic technologies. However, despite a few remarkable proves of concepts, a "killer" nonlinear optical application for these compounds has yet to be found. Because of the absorptive nature of the typically used intraband transitions, it is natural to consider out-of-plane device configurations with a short optical path which also provide additional advantages in terms of phase matching. In this direction, we propose an alternative frequency-resolved optical gating (FROG) scheme for the characterization of ultrafast optical pulses that exploits the remarkable near-zero-index nonlinearities of aluminium zinc oxides thin films. Besides the most obvious technological advantages in terms of manufacturability and cost, our system is demonstrated to outperform commercial modules in key metrics, such as operational bandwidth, sensitivity, and robustness. This general performance enhancement comes with the additional benefit to allow for simultaneous self-phase-matched second- and -third harmonic generation. Because of the widespread use of FROG systems and the fundamental importance of novel methodologies to characterise ultra-fast events, our solution could be of fundamental use for numerous research labs and industries.
Original languageEnglish
JournalNature Communications
Publication statusAccepted/In press - 15 Apr 2022

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