Wang Chenglong, Guo Xiang, Wu Xidong
College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, 310027, China.
School of Information and Electronic Engineering, Zhejiang University of Science and Technology, Hangzhou, 310023, China.
Sci Rep. 2024 Oct 30;14(1):26169. doi: 10.1038/s41598-024-76467-x.
Controlling the nonlinear relationship between surface plasmon polariton (SPP) mode index and chemical potential of graphene can be used in the field of active transformation optics. Here, we propose an electrically tunable 2D Graded Photonic Crystal (GPC) lens based on graphene SPP platform. Our platform comprises a graphene monolayer integrated into a back-gated structure with nano-patterned gate insulators. When the chemical potential of the graphene surface is designed to operate in the nonlinear region, the designed GPC lens can be continuously transformed between a Maxwell's fish-eye lens and a Luneburg lens by tuning the gate voltage. The range of the lens background chemical potential for allowing this transformation is systematically studied. To compensate for the significant errors inherent in the conventional effective medium theory (EMT) during the homogenization of photonic crystals (PCs), we propose a generalized effective medium theory (GEMT). The validity and accuracy of this approach are verified through comparisons with true values (based on rigorous eigenvalue solutions) and EMT values. Due to its advantages of on-site controls and easy fabrication characteristics, the proposed graphene GPC provides a new way for practical on-chip light manipulation.
控制表面等离激元极化激元（SPP）模式折射率与石墨烯化学势之间的非线性关系可应用于有源变换光学领域。在此，我们提出一种基于石墨烯SPP平台的电可调二维梯度光子晶体（GPC）透镜。我们的平台包括集成到具有纳米图案化栅极绝缘体的背栅结构中的单层石墨烯。当石墨烯表面的化学势设计为在非线性区域工作时，通过调节栅极电压，所设计的GPC透镜可以在麦克斯韦鱼眼透镜和伦伯格透镜之间连续变换。系统地研究了允许这种变换的透镜背景化学势范围。为了补偿光子晶体（PCs）均匀化过程中传统有效介质理论（EMT）固有的重大误差，我们提出了一种广义有效介质理论（GEMT）。通过与真实值（基于严格的本征值解）和EMT值进行比较，验证了该方法的有效性和准确性。由于其具有现场控制和易于制造的优点，所提出的石墨烯GPC为实际的片上光操纵提供了一种新方法。
