Ultrasensitive terahertz modulation by silicon-grown MoS₂ nanosheets

Two-dimensional (2D) materials play more and more important roles these days, due to their broad applications in many areas. Herein, we propose an optically-pumped terahertz (THz) modulator, based on Si-grown MoS₂ nanosheets. The broadband modulation effect has been proved by THz time domain spectroscopy and numerical simulation. The modulation depth of this Si-grown MoS₂ nanosheet can reach over 75% under the low pumping power of 0.24 W cm^-2, much deeper than that of bare silicon. By theoretical models and simulation, it is proved that the broadband modulation effect can be described as a free carrier absorption for THz waves in the Drude form. Importantly, by a catalyst mechanism in the Si-grown MoS₂, it is concluded that the MoS₂-Si heterostructure enables the MoS₂ to catalyze more carriers generated on the Si surface. This novel 2D material has a high effective modulation on THz waves under a low pumping power density, which affords it a promising potential in THz applications.