We demonstrate that single layer graphene exhibits a strong nonlinear photon-mixing effect in the terahertz frequency regime. Up to room temperature, the third-order nonlinear current in graphene grows rapidly with increasing temperature. The third-order nonlinear current can be as strong as the linear current under a moderate electric field strength of 10 ~4 V/cm. Because of the unique Dirac behavior of the graphene quasi-particles, low Fermi level and electron fillings optimizes the optical nonlinearity. Under a strong-field condition, the strong-field-induced Dirac fermion population redistribution and nonequilibrium carrier heating effects further amplify the optical nonlinearity of graphene. Our results suggest that doped graphene can potentially be utilized as a strong terahertz photon mixer in the room-temperature regime.
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机译：我们证明了单层石墨烯在太赫兹频率范围内表现出强烈的非线性光子混合效应。在室温下，石墨烯中的三阶非线性电流随着温度的升高而快速增长。在10〜4 V / cm的中等电场强度下，三阶非线性电流可以与线性电流一样强。由于石墨烯准粒子的独特狄拉克行为，低费米能级和电子填充物优化了光学非线性。在强场条件下，强场诱导的狄拉克费米子种群的重新分布和非平衡载流子的加热效应进一步放大了石墨烯的光学非线性。我们的结果表明，在室温条件下，掺杂的石墨烯可以潜在地用作强太赫兹光子混合器。
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