Observation of topological bound states in the continuum in photonic non-Hermitian trimer lattices

We report the first, to the best of our knowledge, experimental observation of non-Hermiticity-induced topological bound states in the continuum in photonic trimer lattices. Using femtosecond laser direct writing technology, we fabricate a series of photonic trimer lattices with precisely tailored loss, enabling systematic investigation of the non-Hermiticity-driven topological phase transition from trivial to nontrivial states. Remarkably, these edge states embed but do not hybridize with bulk states, exhibiting counterintuitive localized properties akin to bound states in the continuum. Our work not only broadens the scope of topological photonic materials but also unveils exciting prospects for future exploration of other remarkable bound states in the continuum.