Observation of paired topological corner states in a femtosecond-laser-written T-graphene photonic lattice

We present the experimental observation of paired topological corner states in a femtosecond-laser-written T-graphene photonic lattice. We construct a nontrivial T-graphene lattice and directly observe the localized propagation of two distinct corner states. Notably, the paired topological corner states coexist in the same band gap and exhibit distinct phase distributions, differentiating them from those in conventional HOTIs. Through numerical simulations and calculations, we confirm that these corner states possess distinct propagation constants and are topologically protected by the unique band structure and lattice symmetry. This work not only establishes a new platform for exploring higher-order topological phenomena but also opens up possibilities for innovative light-manipulation techniques and the design of advanced photonic devices.