Jelver Line, Cox Joel D
POLIMA─Center for Polariton-driven Light-Matter Interactions, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Danish Institute for Advanced Study, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Nano Lett. 2024 Oct 30;24(43):13775-13782. doi: 10.1021/acs.nanolett.4c04048. Epub 2024 Oct 17.
The linear electronic dispersion relation of graphene endows the atomically thin carbon layer with a large intrinsic optical nonlinearity, with regard to both parametric and photothermal processes. While plasmons in graphene nanostructures can further enhance nonlinear optical phenomena, boosting resonances to the technologically relevant mid- and near-infrared (IR) spectral regimes necessitates patterning on ∼10 nm length scales, for which quantum finite-size effects play a crucial role. Here we show that thermoplasmons in narrow graphene nanoribbons can be activated at mid- and near-IR frequencies with moderate absorbed energy density, and furthermore can drive substantial third-harmonic generation and optical Kerr nonlinearities. Our findings suggest that photothermal excitation by ultrashort optical pulses offers a promising approach to enable nonlinear plasmonic phenomena in nanostructured graphene that avoids potentially invasive electrical gating schemes and excessive charge carrier doping levels.
石墨烯的线性电子色散关系赋予了这种原子级薄的碳层较大的固有光学非线性，这在参量和光热过程方面均有体现。虽然石墨烯纳米结构中的等离激元可以进一步增强非线性光学现象，但要将共振提升到技术上相关的中红外和近红外（IR）光谱范围，就需要在约10纳米的长度尺度上进行图案化，而量子有限尺寸效应在其中起着关键作用。在此，我们表明，窄石墨烯纳米带中的热等离激元可以在中红外和近红外频率下以适度的吸收能量密度被激活，而且还能驱动可观的三次谐波产生和光学克尔非线性。我们的研究结果表明，超短光脉冲的光热激发为在纳米结构石墨烯中实现非线性等离激元现象提供了一种有前景的方法，该方法避免了潜在的侵入性电门控方案和过高的电荷载流子掺杂水平。
