Yu Xinyue, Zhuang Suna, Chen Jianfeng, Li Zhi-Yuan, Liang Wenyao
School of Physics and Optoelectronics, South China University of Technology, Guangzhou 510640, China.
State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China.
Nanomaterials (Basel). 2022 Jul 17;12(14):2448. doi: 10.3390/nano12142448.
We have studied the transmission properties of odd/even one-way modes and their reversible conversion in a double-channel waveguide consisting of two magneto-optical photonic crystals (MOPCs) sandwiched with AlO PC. There exist two pairs of even and odd modes, i.e., M1(even)/M2(odd) or M3(odd)/M4(even) modes, for the double-channel waveguides with one- or two-stranded coupling layer of AlO rods, respectively. Among them, the M1, M2, and M3 modes are caused by the weak coupling strength of two sub-waveguides, while the M4 mode results from the strong coupling effect and supports dispersionless slow-light propagation. Furthermore, we realize the reversible conversion between odd and even modes (i.e., between M1 and M2 modes, or M3 and M4 modes) in the one- or two-stranded structure, respectively, by adjusting the length and position of the perfect electric conductor (PEC) defect properly to cause the desired significant phase delay along the upper and lower equivalent transmission paths. Additionally, we find that the robustness of the M1 even mode is poor because of extra excitations of counter-propagation modes near the right Brillouin boundary, while the other three modes have extremely strong robustness against PEC defects and their one-way transmittances are nearly 100%. These results hold promise for many fields, such as slow-light modulation and the design of topological devices.
我们研究了由夹有AlO光子晶体（PC）的两个磁光光子晶体（MOPC）组成的双通道波导中奇偶单向模式的传输特性及其可逆转换。对于分别具有单链或双链AlO棒耦合层的双通道波导，存在两对偶模和奇模，即M1（偶）/M2（奇）或M3（奇）/M4（偶）模式。其中，M1、M2和M3模式是由两个子波导的弱耦合强度引起的，而M4模式是由强耦合效应导致的，并支持无色散慢光传播。此外，我们通过适当调整理想电导体（PEC）缺陷的长度和位置，分别在单链或双链结构中实现了奇模和偶模之间（即M1和M2模式之间，或M3和M4模式之间）的可逆转换，以在上下等效传输路径上引起所需的显著相位延迟。此外，我们发现M1偶模的鲁棒性较差，因为在右布里渊边界附近存在反向传播模式的额外激发，而其他三种模式对PEC缺陷具有极强的鲁棒性，并且它们的单向透过率接近100%。这些结果在慢光调制和拓扑器件设计等许多领域具有应用前景。
