Department of Physics, National University of Singapore, Singapore 117542.
Nano Lett. 2011 Jul 13;11(7):2622-7. doi: 10.1021/nl200587h. Epub 2011 Jun 8.
We present a quantum perturbation theory on two-photon absorption (2PA) in monolayer and bilayer graphene which is Bernal-stacked. The theory shows that 2PA is significantly greater in bilayer graphene than monolayer graphene in the visible and infrared spectrum (up to 3 μm) with a resonant 2PA coefficient of up to ∼0.2 cm/W located at half of the bandgap energy, γ(1) = 0.4 eV. In the visible and terahertz region, 2PA exhibits a light frequency dependence of ω(-3) in bilayer graphene, while it is proportional to ω(-4) for monolayer graphene at all photon energies. Within the same order of magnitude, the 2PA theory is in agreement with our Z-scan measurements on high-quality epitaxial bilayer graphene deposited on SiC substrate at light wavelength of 780 and 1100 nm.
我们提出了一种关于双层和单层 Bernal 堆垛石墨烯中双光子吸收（2PA）的量子微扰理论。该理论表明，在可见和红外光谱（高达 3μm）中，双层石墨烯的 2PA 比单层石墨烯大得多，在半带隙能量处具有高达约 0.2cm/W 的共振 2PA 系数，γ(1) = 0.4eV。在可见光和太赫兹区域，双层石墨烯中的 2PA 表现出与光频率的 ω(-3) 依赖关系，而在所有光子能量下，单层石墨烯的 2PA 与 ω(-4) 成正比。在相同数量级内，该 2PA 理论与我们在 SiC 衬底上外延生长的高质量双层石墨烯在 780nm 和 1100nm 光波长下的 Z 扫描测量结果一致。
