Recently, a research team led by Professors Yun Lai, Ruwen Peng, and Mu Wang from the School of Physics at Nanjing University has made new progress in the study of high-density photonic integration. They demonstrate, for the first time, that multiple independent photonic channels with zero spacing can be realized by introducing deep-subwavelength metallic perturbations on the surfaces of a dielectric slab — a novel zero-spacing waveguide system. This behavior arises from perturbation-engineered suppression of supermode index splitting, achieved by selectively modifying the refractive index of the symmetric mode while leaving that of the antisymmetric mode nearly unchanged. This new principle of flexibly tuning the coupling between zero-spacing waveguides via perturbation engineering opens a broad avenue for the development of future ultra-high-density photonic chips. This work was published in the journal Physical Review Letters, entitled "Zero-Spacing Photonic Channels via Perturbation Engineering" (Phys. Rev. Lett. 137, 073802 (2026)). The first author is Dr. Wenjie Ji (currently a lecturer at Suzhou City University) and this work is in collaboration with Professor Jie Luo from Soochow University.

Figure 1. Schematic of zero-spacing waveguides via perturbation engineering. (a) Modulation of the symmetric mode by metal perturbations. (b) A dielectric slab suffering from crosstalk. (c) Deep-subwavelength metal perturbations isolate adjacent channels without physical cladding, enabling ultra-dense photonic integration.

Publication link: https://doi.org/10.1103/3q3v-hw8n