AI 中文总结
本文发现少层石墨烯多型体在红外波段具有高效上/下转换能力，并通过不对称封装增强二阶非线性，为光纤内产生相关偏振光子对提供可能。
AI 中文摘要
具有破缺反演对称性的材料的光学非线性使得双光子过程成为可能，其中一对入射光子可以产生具有组合频率的上转换光子，或者高能光子可以分裂成一对相关的下转换光子。在此，我们确定了在红外光谱范围内提供上/下转换能力的少层石墨烯薄膜。对于混合堆叠四层（ABCB），即非中心对称的二维晶体，我们发现[ω1,ω2]光子对与能量为0.7eV<Ω=ω1+ω2<1.1eV的光子之间具有高效近共振上/下转换。我们还注意到，在0.7eV<Ω<0.9eV的光谱范围内，通过不对称封装，可以在菱面体三层和四层中增强显著的二阶非线性。对于涂覆少层石墨烯的光纤，这可能为“光纤内”生产具有相关偏振的光子对打开大门。
英文摘要
Optical nonlinearity of materials with broken inversion symmetry enables two-photon processes where an incoming pair of photons can generate an up-converted photon with the combined frequency, or a high-energy photon can be split into a correlated pair of down-converted photons. Here, we identify few-layer graphene films that offer up/down-conversion capability in the infrared spectral range. For mixed stacking tetralayers (ABCB), which are non-centrosymmetric 2D crystals, we find highly efficient nearly resonant up/down-conversion of [$ω_1,ω_2$] photon pairs into/from a photon with $0.7$eV$<Ω=ω_1+ω_2<1.1$eV. We also note that a pronounced second-order nonlinearity in the spectral range of $0.7$eV$<Ω<0.9$eV can be promoted in rhombohedral tri- and tetralayers by asymmetrical encapsulation. Potentially, for fibers coated with few-layer graphene, this opens the door for ``in fiber" production of photon pairs with correlated polarizations.
Comments6 pages, 3 figures
