We propose a method to realize topological rainbow concentrator based on synthetic dimension. This work is published in Physical Review Letters.
Synthetic dimension provides a new platform for realizing topological photonic devices. We realize a topological rainbow concentrator by constructing a synthetic dimension. The synthetic dimension is constructed using a translational degree of freedom of the nanostructures inside the unit cell of a two-dimensional photonic crystal. The translational deformation induces a nontrivial topology in the synthetic dimension, which gives rise to robust interface states at different frequencies. The topological rainbow can trap states with different frequencies, controlled by tuning the spatial modulation of interface state group velocities. The operation frequency as well as the bandwidth of the topological rainbow can be easily tuned by controlling the band gap of the photonic crystal.
Our work provides a universal method for the realization of topological rainbow concentrators based on the notion of synthetic dimension, and it will enable practical applications such as topological routers and optical information processing.
Fig. 1. Topological rainbow concentrator constructed in the synthetic dimension.