We report on experimental studies of terahertz (THz) radiation transmission through grating-gate graphene-channel transistor nanostructures and demonstrate room temperature THz radiation amplification stimulated by current-driven plasmon excitations. Specifically, with increase of the dc current under periodic charge density modulation, we observe a strong red shift of the resonant THz plasmon absorption, its complete bleaching, followed by the amplification and blue shift of the resonant plasmon frequency. Our results are, to the best of our knowledge, the first experimental observation of energy transfer from dc current to plasmons leading to THz amplification. We present a simple model allowing for phenomenological description of the observed amplification phenomena. This model shows that in the presence of dc current the radiation-induced correction to dissipation is sensitive to the phase shift between THz oscillations of carrier density and drift velocity, and with increase of the current becomes negative, leading to amplification. The experimental results of this work as all obtained at room temperature, pave the way towards the new 2D plasmons based, voltage tuneable THz radiation amplifiers.

中文翻译：

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栅栅石墨烯结构在室温下太赫兹辐射的放大

我们报告了通过栅栅石墨烯沟道晶体管纳米结构进行太赫兹（THz）辐射传输的实验研究，并证明了由电流驱动的等离子体激元激发的室温THz辐射放大。具体而言，随着周期性电荷密度调制下直流电流的增加，我们观察到谐振THz等离子体激元吸收发生了强烈的红移，它的完全漂白，接着是谐振等离子体激元频率的放大和蓝移。据我们所知，我们的结果是对从直流电流到等离子激元的能量转移（导致太赫兹放大）的首次实验观察。我们提出了一个简单的模型，允许对观察到的扩增现象进行现象学描述。该模型表明，在存在直流电流的情况下，辐射引起的耗散校正对载流子密度和漂移速度的太赫兹振荡之间的相移很敏感，并且随着电流的增加变为负值，从而导致放大。这项工作的实验结果都是在室温下获得的，这为基于新型2D等离子体激元，电压可调THz辐射放大器的发展铺平了道路。