Elimination of Spatial Hole Burning in Microlasers for Stability and Efficiency Enhancement

Optical gain and loss are considered as a pair of feuds. It is widely believed that optical loss is the most detrimental factor in laser systems that decreases the laser efficiency. The hitherto approach is to minimize or even avoid any loss in designing any laser systems. From an opposite vantage point, however, we demonstrate that harnessing additional optical losses enables an energy-efficient microlaser with a robust single-mode lasing action even in the nonlinear regime above lasing threshold. This is due to elimination of the undesired spatial hole burning effect by tailoring the complex index modulations at an exceptional point (EP), thereby spatially maximizing the interaction of optical gain material with light field in a homogeneous fashion. Approximately 2x enhancement in the laser slope efficiency is observed, enabled by elimination of spatial hole burning. This result is expected to reposition a strategic role of optical losses in laser systems, advancing fundamental laser physics and promising novel technologies in energy-efficient photonic systems.