Nonlinear Dynamics in Semiconductor Ring Lasers: From Phase Turbulence to Solitons

The recent study of ring quantum cascade lasers [1] , [2] (QCLs, Fig. 1a ) revealed a new laser instability. It is triggered by phase turbulence akin to the wave instabilities that occur in other nonlinear systems such as fluids, superconductors and Bose-Einstein condensates. The choice of the ring geometry took inspiration from Kerr combs [3] , that are commonly generated in passive ring microresonators and have attracted great attention within the photonics community in the last years thanks to their rich physics.