Reversible Conversion of Odd/Even One-Way Modes in Magneto-Optical Photonic Crystal Double-Channel Waveguides

Abstract

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 Al2O3 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 Al2O3 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.

Topological slow light waveguide in photonic valley-locked heterostructures

“…The results of finite element method (FEM) calculations prove that the topological slow-light waveguide mode (TSWM) with large n g of 100 can support topological properties, including valley locking and being immune to backscattering. Importantly, compared to previous work on topological slow light [22][23][24][25][26][27][28][29], our method provides an efficient way to achieve slow-light mode with high flux transport, which is easy for integration with conventional photonic crystal waveguides. Our findings may find topological slow light applications such as optical buffers, the processing of optical signals, optical delay lines and so on.…”

“…Recently, slow-light mode in topological waveguides has received more and more attention, which can achieve topologically protected transport. Some methods for topological slow light have been proposed in previous reports, including strong coupling between edge states in gyromagnetic photonic crystals [22,23], band winding in high-momentum space [24,25] and VPC-based interface modification [26][27][28]. However, these slow-light waveguides are based on topological edge states, which are localized along a single domain wall.…”