Degenerate band edge laser with enhanced local density of optical states for threshold reduction

A single longitude mode degenerate band edge (DBE) laser based on an asymmetric coupled periodic waveguides structure has been fabricated. Symmetry breaking enables the coupling of originally decoupled odd and even modes, and this degeneracy leads to the formation of the DBE. The occurrence of the DBE and the associated enhancement of the local density of optical states (LDOS) have been theoretically validated. Compared to lasers under regular band edge (RBE) conditions, DBE lasers achieved a 22% reduction in threshold current density in single-mode operation through the enhancement of LDOS, without significant loss in output power. Our findings have, to a certain extent, paved the way for achieving low-threshold operation in lasers with macroscopic resonators.