Impact of fabrication disorder on lasing near a stationary inflection point

Traditional lasing and control theory are applied to the investigation of a third-order exceptional point of degeneracy (EPD), associated with a stationary inflection point (SIP) of the Bloch dispersion relation. Specifically, we consider the case of a three-path periodic optical waveguide with distributed Bragg reflectors. We characterize the resonances and the field amplitude enhancement of a lossless and gainless waveguide operating near a SIP. Afterward, the gain is introduced, and the lasing threshold is identified as the peak of the transfer function. The SIP enhances light–matter interactions in active (with gain) media for low-threshold lasing with an inverse cubic scaling of the lasing threshold with device length. The impact of fabrication disorder and other non-idealities on the anomalous lasing threshold scaling with device length is studied, and we show that the scaling is maintained even in the presence of modal index variations. This shows promise for the practical realizability of SIP-based low-threshold lasing devices.