Thesis Defense In Chemistry, Presented by Chun-Ying Huang
Polarization Waves in Two-dimensional Ferroelectrics
Two-dimensional (2D) van der Waals (vdW) ferroelectrics are promising for on-chip nonline- ar photonics, yet their development is hindered by a limited material library. In this presentation, I establish the 2D vdW ferroelectric NbOL 2 as a highly efficient, integrable terahertz (THz) source. NbOl 2 exhibits a giant second-order nonlinear susceptibility in the ferroelectric phase, enabling THz wave generation via optical rectification comparable to commercial bulk ZnTe. Leveraging the vdW integrability, we construct a near-field THz probe for sub-diffraction-limit spectroscopy by stacking NOl 2 on top of a target sample. Furthermore, I will report the observation of an anomalous narrowband THz emission from submicron NbOl 2 flakes. I will elucidate its origin as the radiation of polarization waves-the collective excitation of the ferroelectric order-and demonstrate its chemical tunability via halogen substitution. Overall, this work advances NbOl 2 for scalable THz photonics and uncovers the polarization waves of 2D ferroelectrics.
Zoom Link: https://columbiauniversity.zoom.us/j/93436362807?pwd=zSvtmrBAEZqxMHvydFeHJNxcGeFOrh.1
Meeting ID: 934 3636 2807
Passcode: 748013
