Download file (1.77 MB)
Download as zip (1.18 MB)

Collection

Citation

Description:

Optical nonlinearities of bound electrons reveal information about both the in-plane rotational and out-of-plane inversion symmetries of a crystal. In the van der Waals material hexagonal boron nitride (hBN) both these symmetries and the linear vibrational properties have led to the rich physics of mid-infrared phonon-polaritons. However, the role of strong electron-phonon nonlinearities requires further study. In this work, we investigate both theoretically and experimentally the rich interplay of ionic anharmonicity and symmetry in phonon-polariton mediated nonlinear optics. We show that large enhancements (>30×) of third-harmonic generation occur for incident femtosecond pulses that are resonant with the hBN phonons. In addition, we predict and observe transient sub-picosecond duration second-harmonic signals during resonant excitation, which in equilibrium is forbidden by symmetry. This surprising result indicates that inversion symmetry breaking of the crystal can be optically induced and controlled via phonon interactions by both the power and polarization of the pump laser.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Polar crystals, optical nonlinearities, hexagonal boron nitride

Date published: 2023-11-24

Publisher: Springer Science and Business Media LLC

Journal:

• Nature Communications (ISSN: 20411723) vol. 14 issue. 1 7685

Funding:

• National Science Foundation PHY-2110615
• National Science Foundation PHY-2110615
• National Science Foundation PHY-2110615
• U.S. Department of Energy DE-SC0019443
• U.S. Department of Energy DE-SC0019443

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1038/s41467-023-43501-x

Related item:

Other identifier(s):

Contact agent:

Updated at: 2025-02-11 12:30:15 +0900

Published on MDR: 2025-02-11 12:30:16 +0900