单层与双层石墨烯的光学吸收性质研究*
Optical absorptions in monolayer and bilayer graphene
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摘要: 采用紧束缚模型分别描述单层、双层石墨烯的能带结构,利用光子-电子相互作用的二阶微扰理论分别计算单光子和双光子吸收系数.计算结果表明:单层石墨烯单光子吸收系数为常数,约为6.8×107 m?1,即单层石墨烯对入射光的吸收率约为2.3%;双层石墨烯的单光子吸收比单层石墨烯的单光子吸收强,且随入射光波长呈分段性变化.单层石墨烯的双光子吸收系数与波长λ4成正比;双层石墨烯双光子吸收系数在红外波段(~3100 nm处)有一个很强的共振吸收峰.研究结果可为石墨烯材料在光电子器件的研究和制作方面提供指导.Abstract: We theoretically simulate one-photon and two-photon absorption spectra for monolayer and bilayer graphene employing the second-order perturbation theory of the electron-photon interaction. The tight-binding model is used to describe the band structure of graphene. The results show that one-photon absorption coefficient of monolayer graphene is a constant about 6.8 × 107 m?1, demon-strating that the absorptivity of incident light in monolayer graphene approximates to 2.3%. The one-photon absorption coefficient of bilayer graphene changes sectionally with the wavelength and is greater than that of monolayer graphene. The two-photon absorption coefficient of monolayer graphene is proportional toλ4 . The two-photon absorption coefficient of bilayer graphene exhibits a giant resonance absorption peak in the infrared (~3100 nm) region. Our results will provide theoretical guidance for the application of graphene in the research field of optoelectronic devices.
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