Chen Shanshan, Zhang Weixuan, Yang Bing, Wu Tong, Zhang Xiangdong
Beijing Key Laboratory of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China.
School of Physical Science and Information Engineering, Liaocheng University, Shandong, 252059, China.
Sci Rep. 2019 Apr 3;9(1):5551. doi: 10.1038/s41598-019-42092-2.
We theoretically demonstrate that tunable exceptional points (EPs) can be realized by using graphene-embedded one-dimensional (1D) photonic crystals with optical pumping in the terahertz (THz) frequency range. By tuning the Fermi level of graphene sheet, the energy band are altered significantly and the EP appears. In particular, multiple EPs at different frequencies can be selectively produced via subtly adjusting the band structure. Furthermore, topological features of these EPs, such as crossing and anti-crossing of the real and imaginary parts of the eigenvalues, have been analyzed in detail. We expect that tunable EPs can provide an instructive method to design active optical devices based on photoexcited graphene sheets in the THz frequency range.
我们从理论上证明，通过在太赫兹（THz）频率范围内对嵌入石墨烯的一维（1D）光子晶体进行光泵浦，可以实现可调谐的奇异点（EPs）。通过调节石墨烯片的费米能级，能带会发生显著变化，奇异点随之出现。特别地，通过巧妙调整能带结构，可以选择性地产生不同频率的多个奇异点。此外，还详细分析了这些奇异点的拓扑特征，如本征值实部和虚部的交叉与反交叉。我们期望可调谐奇异点能够为在太赫兹频率范围内基于光激发石墨烯片设计有源光学器件提供一种有指导意义的方法。
