posted on 2024-02-22, 10:33authored byChen Wang, Yong Tan, Yongzheng Wen, Shiqiang Zhao, Kaixin Yu, Jingbo Sun, Ji Zhou
The nonlinearities at terahertz (THz) frequencies have
been recognized
as key and promising approaches to advance the development of high-frequency
THz sources via the harmonic generation process, which lies at the
core of THz technology. However, the high-performance nonlinear THz
materials possessing extreme conversion efficiency, high-volume on-chip
integration, and room-temperature operation are still seemingly missing.
Here, we propose a nonlinear metasurface for efficient THz third-harmonic
generation (THG) based on the nonperturbative nonlinearity of doped
silicon. By integrating aluminum grating, the significantly enhanced
local field drives the intrinsic nonlinearity of silicon to the nonperturbation
regime, where the conversion efficiency of THz THG approaching maximum
can be achieved under moderate pump from table-top sources at ambient
temperature. The measurements demonstrate that the nonlinear responses
of metasurfaces are ∼1000 times stronger than the plain silicon
film. Such a platform also allows us to experimentally obtain the
nonlinear susceptibilities of silicon at perturbation and nonperturbation
regimes, which are crucial for understanding the essences of nonlinear
THz–matter interactions but scarcely available for most materials
in this part of the spectrum. Our findings may open an avenue toward
CMOS-compatible, room-temperature, and efficient THz sources and nonlinear
electronics.