基于硅基石墨烯的全光控太赫兹波强度调制系统研究

在太赫兹通信等系统中需要利用太赫兹波调制器对信号进行调制.基于GaAs 等传统半导体材料设计和制作的调制器在太赫兹波段的响应过低,因而很难应用于太赫兹系统.为了弥补传统调制技术在带宽和调制深度不够的缺点,设计了一种全新的基于硅基石墨烯的全光控太赫兹强度调制系统.该调制系统利用材料中光生载流子对太赫兹波的吸收特性,通过调节照射到材料上的可见光光强来改变光生载流子浓度,从而实现对太赫兹波强度调制.从理论和实验两方面对这种新型太赫兹强度调制系统的调制深度和调制带宽进行了研究.研究结果表明,在泵浦光功率密度为18 mW/mm2时,该调制系统能在实验使用的THz-TDS 测试系统(0.1~2.5 THz)的整个频谱范围内进行有效的调制,调制深度可达到12 %.且随着泵浦光能量的增大,调制深度增大.

Graphene-on-silicon based all-optically-driven terahertz wave intensity modulation

Most of terahertz (THz) systems and their application require THz modulator to modulate THz signals. Photoelectric modulators at present are made and producted by semiconductor-based, such as GaAs, materials. But unfortunately, due to their limited response to THz wave, these modulators based on traditional semiconductors are not suitable for THz systems. To overcome the limitation on modulation bandwidth and depth, a new scheme of THz wave intensity modulation system was proposed, which was based on all optically tuned graphene on silicon(GOS). This new modulation system was realized by photo-induced free carrier, which can absorb THz waves. By controlling light intensity which incident on modulator, photo-induced carrier density could be tuned, and even transmitted THz wave intensity was modulated. In this work, the fundamental properties of this THz intensity modulator was theoretically and experimentally studied , such as modulation depth and bandwidth. Our experiment results also show that it has a wide modulation bandwidth, which can modulate efficiently THz wave in THz-TDS of frequency range from 0.1 to 2.5 THz, and the typical modulation depth is 12 % at an optical pump fluence of 18 mW/mm2. what's more, the modulation depth increases with increasing optical pump fluence.