Enhanced Terahertz Generation From the Lithium Niobate Metasurface

The lithium niobate (LiNbO 3 ) metasurface is an attractive platform for nonlinear frequency conversion due to its excellent nonlinearity, high damage threshold, and strong enhancement of the driving field. Here, we demonstrated the nonlinear metasurface for terahertz (THz) generation from LiNbO 3 on an insulator. The THz electric field from the LiNbO 3 metasurface of 300 nm thickness is enhanced by more than one order of magnitude compared to the unstructured sample. The enhanced terahertz electric field is very selective in the excitation wavelength due to its resonant feature and is highly anisotropic with respect to the excitation polarization. The polarization direction of the THz electric field can be controlled by rotating the optical axis of the LiNbO 3 metasurface. By combining the nanofabrication technology of the LiNbO 3 metasurface and ultrafast nonlinear optics, our work paves the way for the design of new compact terahertz photonic devices that integrate THz emitters into LiNbO 3 -based chips with multifaceted capabilities.