Cui Wen Yi, Zhang Jingjing, Gao Xinxin, Cui Tie Jun
State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China.
Institute of Electromagnetic Space, Southeast University, Nanjing 210096, China.
Nanophotonics. 2021 Dec 1;11(9):1913-1921. doi: 10.1515/nanoph-2021-0539. eCollection 2022 Apr.
We propose an ultrathin reconfigurable Mach-Zehnder interferometer (MZI) for realizing dynamic frequency and amplitude modulations of spoof surface plasmon (SSP) signal. Active varactor diodes are integrated in the SSP unit cells on one of the MZI arms to introduce asymmetry to the MZI structure, which can control the interference patterns by varying bias voltages applied on the varactor diodes. We show that the spectral positions of multiple sharp interference dips are very sensitive to the change of diode capacitance, thereby allowing for good frequency modulation. We also demonstrate continuous amplitude modulation by tuning the varactor diodes at multiple selected frequencies. To verify the reconfigurable feature of the proposed SSP MZI, the frequency shift keying (FSK) and amplitude modulations have been experimentally demonstrated on the same structure. The modulation depth of the amplitude modulation can be further improved by designing geometrical parameters of the SSP structure, reaching a significant amplitude change from 0.88 to 0.05 in experiments.
我们提出了一种超薄可重构马赫-曾德尔干涉仪（MZI），用于实现欺骗表面等离子体（SSP）信号的动态频率和幅度调制。有源变容二极管集成在MZI一个臂上的SSP单元中，以引入MZI结构的不对称性，这可以通过改变施加在变容二极管上的偏置电压来控制干涉图样。我们展示了多个尖锐干涉凹陷的光谱位置对二极管电容的变化非常敏感，从而实现良好的频率调制。我们还通过在多个选定频率上调谐变容二极管来演示连续幅度调制。为了验证所提出的SSP MZI的可重构特性，在同一结构上通过实验演示了频移键控（FSK）和幅度调制。通过设计SSP结构的几何参数，可以进一步提高幅度调制的调制深度，在实验中实现了从0.88到0.05的显著幅度变化。
