Single-Wall-Carbon-Nanotube-VSe2 Nanohybrid for Ultrafast Visible-To-Near-Infrared Third-Order Nonlinear Optical Limiters

An ideal third-order nonlinear optical material, which can efficiently absorb and refract light over a broad spectral range, is of both fundamental and technological significance as it enables many helpful functionalities in photonics. However, the optical nonlinearities are rather weak due to their perturba-tive nature and are limited to electronic resonances, thus restricting the response to a narrow spectral range. A charge-coupled donor-acceptor material pair can enhance the nonlinear optical response and cir-cumvent the narrow spectral range limitation. However, such studies on potential material pairs remain largely unexplored. Here, we report the experimental observation of ultrafast third-order nonlinear optical response spanning the entire visible-to-near-infrared (400-900 nm) region in single-wall-carbon-nanotube (SWCNT)-VSe2 nanohybrid in the strong coupling regime, enabled by efficient charge transfer. Compared to control systems, the measured nonlinear absorption and refraction of the nanohybrid show unprece-dented or many-fold enhancements. Further, our density-functional theory and Bader-charge analysis show the strong electronic coupling of the nanohybrid in which the electrons are transferred from VSe2 to SWCNT, verified by steady-state and time-resolved photoluminescence measurements. The physics of the ultrafast nonlinear optical response is well captured by our five-level rate-equation model both qualita-tively and quantitatively. Using the nanohybrid, we design a liquid cell-based optical limiter with an order of magnitude better device performance parameters, such as the optical limiting onset (2.5-8.0 mJ cm-2) and the differential transmittance (0.42-0.62), compared to several other benchmark optical limiters in the femtosecond regime.

Automated summary

An experimental observation of ultrafast third-order nonlinear optical response spanning the entire visible-to-near-infrared region in SWCNT-VSe2 nanohybrid is reported. The strong electronic coupling and efficient charge transfer in the nanohybrid result in unprecedented enhancements in nonlinear absorption and refraction. The nanohybrid also demonstrates superior performance as an optical limiter.