Li Junhao, Zhang Tian, Chen Lin
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China.
State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing, 100876, China.
Nanoscale Res Lett. 2018 Oct 25;13(1):338. doi: 10.1186/s11671-018-2750-8.
Benefiting from the large third-order nonlinear susceptibility of graphene and significantly enhanced field intensity of graphene plasmons (GPs), graphene has shown great potentials to enhance plasmonic third-harmonic generation conversion efficiency. However, it still lacks an effective configuration that can excite the fundamental frequency (FF) GPs and guide the generated third-harmonic frequency (THF) GPs simultaneously. Here, we have proposed a diffractive silicon grating underneath a graphene sheet to generate and transmit THF GPs. The FF GPs are efficiently excited by illuminating a normal-incidence plane wave due to guided-mode resonance and then are converted to the THF GPs with a large conversion efficiency, originating from the giant field intensity of the FF GPs. We numerically demonstrate that, a large third-harmonic generation conversion efficiency of 3.68 × 10 can be realized with a small incident power density of 0.19 MW/cm at 28.62 μm. Furthermore, the generated THF GPs can be efficiently guided along low-loss GP waveguides that are connected to both sides of grating section. Our results can stimulate making graphene-based light sources for mid- and far-infrared silicon photonics.
得益于石墨烯的大三阶非线性极化率以及石墨烯等离激元（GPs）显著增强的场强，石墨烯在提高等离激元三次谐波产生转换效率方面展现出巨大潜力。然而，它仍然缺乏一种能够同时激发基频（FF）GPs并引导所产生的三次谐波频率（THF）GPs的有效结构。在此，我们提出在石墨烯片下方设置一个衍射硅光栅来产生并传输THF GPs。由于导模共振，通过照射垂直入射的平面波可有效激发FF GPs，然后由于FF GPs的巨大场强，FF GPs以高转换效率转换为THF GPs。我们通过数值模拟证明，在28.62μm波长下，当入射功率密度低至0.19 MW/cm²时，可实现高达3.68×10⁻⁴的大三阶谐波产生转换效率。此外，所产生的THF GPs能够沿着连接到光栅部分两侧的低损耗GP波导高效地进行引导。我们的研究结果能够推动基于石墨烯的中红外和远红外硅光子学光源的制造。
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