Exceptional Topological Surface Laser
Band topology has been studied as a design principle of realizing robust
boundary modes. Here, by exploring non-Hermitian topology, we propose a
three-dimensional topological laser that amplifies surface modes. The
topological surface laser is protected by nontrivial topology around
branchpoint singularities known as exceptional points. In contrast to
two-dimensional topological lasers, the proposed three-dimensional setup can
realize topological boundary modes without judicious gain at the edge or
symmetry protection, which are thus robust against a broad range of disorders.
We also propose a possible optical setup to experimentally realize the
topological surface laser. Our results provide a general guiding principle to
construct non-Hermitian topological devices in three-dimensional systems.