Impedance-controlled Laser Dynamics in Near-Zero Index Media

Abstract

Near-zero-index (NZI) media have been explored for controlling spontaneous emission, but their impact on stimulated emission and lasing properties remains unexplored within their different classes, i.e., epsilon-near-zero (ENZ), mu-near-zero (MNZ), or epsilon-and-mu-near-zero (EMNZ). Here, we show theoretically that lasing emission depends on the class of NZI medium and can be controlled through its impedance. The major difference, as compared to conventional laser media, arises from the incorporation of dispersive electric and magnetic properties in the derivation of the Maxwell Boch equations. In this framework, the analysis of laser rate equation reveals that the ENZ class, with high impedance, can reduce the lasing threshold through enhanced electric-field interaction. Numerical simulations further show that the NZI class also governs the spectral response: whereas ENZ and MNZ classes suffer from multimode emission, the EMNZ class preserves single-mode emission.