双层石墨烯的单光子与双光子吸收理论研究

Theoretical Research of Single-Photon and Two-Photon Absorption in Bilayer Graphene

采用紧束缚模型描述双层石墨烯的电子能带结构，得到相应的本征值和本征函数,并利用入射光子与电子相互作用的微扰理论分别计算单光子吸收（SPA）和双光子吸收（TPA）系数，系统地分析了入射光子能量和电子弛豫时间对双光子吸收的影响。计算结果表明：双层石墨烯的单光子吸收系数随入射光波长呈分段性变化，当入射光波长大于3100 nm时，单光子吸收系数为常数，约为2.1×108 m^-1；双层石墨烯的双光子吸收在红外波段（波长约为3100 nm）处有一个很强的共振吸收峰，吸收系数的量级为10^-4 m/W。研究结果为双层石墨烯在光子学和光电子学方面的应用提供理论指导。

The tight-binding model is employed to describe the band structure of bilayer graphene, obtaining the corresponding eigenvalue and eigenfunction. It is easy to simulate the single-photon absorption（SPA） and two-photon absorption （TPA） coefficient in bilayer graphene theoretically using the second-order perturbation theory of the electron-photon interaction. The TPA which is affected by the incident photon energy and electronic relaxation time is analysed systematically. The results show that the SPA coefficient of bilayer graphene changes sectionally with the wavelength and approximates 2.1×108 m^-1 when the wavelength is longer than 3100 nm. The TPA coefficient of bilayer graphene appears a giant resonance absorption peak in the infrared （wavelength is about 3100 nm） region. The results will provide theoretical guidance for the application of bilayer graphene in the field of photonics and optoelectronics.