Thouless Pumping of Superposition Modes in Photonic Lattices by Employing Multiple Energy Bands

Abstract

Thouless pumping enables the topological transport of particles or waves governed by a topological invariant, which is especially useful for integrated photonic applications. Photonic Thouless pumps typically make use of one energy band to realize the topological transport of light localized in a single site, which however hinders them from applications for manipulating superposition modes localized in multiple sites. Here, this problem is tackled by engineering multiple energy bands of the Thouless pump. By constructing a superposition mode that occupies multiple energy bands with the same Chern number, topological transport of superposition modes localized in multiple sites can be realized. A femtosecond laser written photonic lattice featuring the off-diagonal Aubry-André-Harper model is experimentally employed to demonstrate the topological transport of light localized in up to four waveguides. The proposed superposition mode based Thouless pump is promising for applications such as on-chip robust optical routing with high capacity.