Electrically injected terahertz (THz) radiation sources are extremely appealing, given their versatility and miniaturization potential, opening the venue for integrated-circuit THz technology. In this work, we show that coherent THz frequency combs in the range 0.5 THz < ω/2π < 10 THz can be generated, making use of graphene plasmonics. Our setup consists of a graphene field-effect transistor with asymmetric boundary conditions, with the radiation originating from a plasmonic instability that can be controlled by direct current injection. We put forward a combined analytical and numerical analysis of the graphene plasma hydrodynamics, showing that the instability can be experimentally controlled by the applied gate voltage and the injected current. Our calculations indicate that the emitted THz comb exhibits appreciable temporal coherence (g⁽¹⁾(τ) > 0.6) and output irradiance (10⁸ Wm^–2). This makes our scheme an appealing candidate for a graphene-based THz laser source. Moreover, a mechanism for the instability amplification is advanced for the case of substrates with varying electric permittivity, which allows to overcome eventual limitations associated with the experimental implementation.

中文翻译：

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石墨烯场效应晶体管中的太赫兹激光梳

考虑到其多功能性和小型化潜力，电注入的太赫兹（THz）辐射源极具吸引力，这为集成电路THz技术开辟了场所。在这项工作中，我们表明利用石墨烯等离激元可以产生0.5 THz <ω/2π<10 THz范围内的相干THz频率梳。我们的装置由具有非对称边界条件的石墨烯场效应晶体管组成，其辐射源自可通过直流注入控制的等离激元不稳定性。我们提出了对石墨烯等离子体流体动力学的综合分析和数值分析，表明不稳定性可以通过施加的栅极电压和注入电流实验控制。我们的计算表明，发射的太赫兹梳具有明显的时间相干性（g ^（1）（τ）> 0.6）和输出辐照度（10 ⁸ W m ^–2）。这使我们的方案成为基于石墨烯的太赫兹激光源的有吸引力的候选方案。此外，针对具有变化的介电常数的基板的情况，提出了用于不稳定性放大的机制，这允许克服与实验实施相关的最终限制。