Owing to the inherent robustness to fabrication flaws or imperfections, topological photonics has provided a defect-tolerant strategy for the design of chip-integrated photonic devices. A multi-waveguide array is one of the most popular systems for demonstrating topological photonics and can be designed by adjusting couplings between adjacent waveguides based on Su-Schrieffer-Heeger model. However, the current strategies for generating topological photonics modes on a chip require bulky structures, which is against high-density optical integration.
The team of Prof. Lin Chen from Wuhan National Laboratory for Optoelectronics provides a metasurface-enabled coupler to convert the propagating waves into the aimed photonic topological modes on a chip. With carefully designed metasurfaces loading on waveguide arrays, the transverse momentum mismatch between the topological modes and vertically incident light can be compensated. By carefully arranging the numbers, the locations and the orientation angles of metasurface units upon each waveguide, and the intensity and phase distributions of the topological modes can be matched.
The meta-coupler arrays for the generation of topological interface mode and topological symmetrical/anti-symmetrical edge modes are designed and numerically demonstrated. The working bandwidth of these meta-coupler arrays are all larger than 40 nm, and the working angle ranges are all larger than 10 degrees. The presented strategy for generating topological modes can also be universally extended to produce arbitrary supermodes in waveguide arrays.
Recently, this work, titled as “Meta-coupler arrays linking propagating waves and photonic topological modes on a chip”, was published in Optics Letters.
Paper link: https://doi.org/10.1364/OL.453234
Fig. 1. Schematic of the proposed meta-coupler for generating photonic topological modes.
(a) Generating a topological interface mode; (b) Generating a topological edge mode.
Fig. 2. The generated topological interface mode.
(a) Distribution of the Ey. (b) Mode purity and coupling efficiency versus wavelength.
