We investigate optical nonlinearities that are induced and enhanced due to the strong phonon resonance in hexagonal boron nitride. We predict and observe large sub-picosecond duration signals due to four-wave mixing (FWM) during resonant excitation. The resulting FWM signal allows for time-resolved observation of the crystal motion. In addition, we observe enhancements of third-harmonic generation with resonant pumping at the hBN transverse optical phonon. Phonon-induced nonlinear enhancements are also predicted to yield large increases in high-harmonic efficiencies.
@article{arxiv.2107.11959,
title = {Phonon-Enhanced Nonlinearities in Hexagonal Boron Nitride},
author = {Jared S. Ginsberg and M. Mehdi Jadidi and Jin Zhang and Cecilia Y. Chen and Nicolas Tancogne-Dejean and Sang Hoon Chae and Gauri N. Patwardhan and Lede Xian and Kenji Watanabe and Takashi Taniguchi and James Hone and Angel Rubio and Alexander L. Gaeta},
journal= {arXiv preprint arXiv:2107.11959},
year = {2023}
}