A five-band metamaterial absorber (MMA) based on a simple planar structure is proposed. It utilizes different areas of a single unit cell to match impedance, and produces different absorptive frequencies. Numerical calculation shows that the MMA has five different absorption peaks at 3.78 GHz, 7.66 GHz, 10.9 GHz, 14.5 GHz and 16.7 GHz, and their absorption rates reach 95.5%, 98.6%, 95.7%, 96.6% and 99.8%, respectively. The proposed structure is polarization insensitive for transverse electric (TE) and transverse magnetic (TM) incident waves. Also, the absorptive characteristics over large incident angles are examined. In addition, we analyze the absorption mechanism by the surface current density and power flow density distributions. This simple structure provides a way to design multi-band MMA, and also saves the cost of fabrication.

研究了一种新型全光纤可调光衰减器,设计了耦合特性检测装置。基于耦合波理论,分析了衰减量与改变参量之间的关系,讨论了波长微损耗特性。实验结果表明,调节两光纤锥横向间距u可以实现衰减量的大幅度调节,衰减量接近30 dB;调节纵向耦合长度L可以实现衰减量的微调,衰减量可达37 dB;此可调光衰减器可以获得<0.2 dB的波长微损耗。利用此结构的衰减器能够较理想地削弱或控制光信号,在对气体进行浓度测量和组分识别时,利用波长微损耗特性能够确保气体浓度测量的可靠性和单值性。