基于离轴级联超表面的轨道角动量解复用系统设计

Design of an orbital angular momentum demultiplexing system based on off-axis cascaded metasurfaces

设计超表面系统时,实际制作的超表面效率与理论设计效率相差较大,常会存在超表面调制效率不足产生的杂散光,这些杂散光作为背景噪声在级联超表面系统中的影响会逐级放大,影响系统功能。为了降低有限效率的超表面对系统性能的影响,本文提出了一种基于离轴级联超表面的轨道角动量解复用系统设计方法。这一工作通过加入离轴相位设计,有效消除了级联超表面系统中因超表面效率降低所产生的杂散光。利用FDTD(时域有限差分)仿真软件进行计算和验证,结果表明,离轴级联超表面系统能有效减少因调制效率不足而产生的杂散光,与同轴系统相比,实现了最大串扰降低4.15 dB以及平均80%的杂散光消除,展现出较大的性能优势。

When designing metasurface systems,the actual efficiency of the metasurface is much different from the theoretical design efficiency.This can lead to stray light caused by insufficient modulation efficiency of the metasurfaces,which acts as background noise and is magnified in cascaded metasurface systems step by step,affecting system functionality.To reduce the impact of metasurfaces with limited efficiency on system performance,this paper proposes a design method for an orbital angular momentum demultiplexing system based on off-axis cascaded metasurfaces.By incorporating an off-axis phase design,the stray light generated by the reduced efficiency of the metasurface in a cascaded metasurface system is effectively eliminated.Using FDTD(finite difference time domain)simulation software for calculation and validation,the results demonstrate that the off-axis cascaded metasurface system can effectively reduce stray light caused by insufficient modulation efficiency.Compared to the on-axis system,it achieves a maximum reduction in crosstalk of 4.15 dB and an average of 80%stray light elimination,showing a significant performance advantage.