Möbius Laser Cavity Soliton Microcomb

A highly promising approach to maintaining the integrity of a state under perturbations through nonlinear topological protection has been demonstrated in driven fibre loops [1]. This approach ensures that the state remains intact even in the presence of bifurcation induced by spontaneous symmetry breaking (SSB) in parametric generation. A key question is whether this topological protection can extend beyond parametric generation to complex states, such as lasing systems, that involve multiple nonlinear frequencies. A microresonator-filtered laser (Fig. 2a) offers flexibility in positioning the resonating laser modes within the microcavity (Fig. 2b) [2]. In a standard configuration, the Kerr microcavity aligns in group velocity with the lasing cavity. Lasing modes can be grouped as per their distinct detuning, enabling us to differentiate the stability and existence regions for specific groups of modes, which display different lasing thresholds. A simple method to move in this region is to adjust the laser cavity length so that the roundtrips of the two cavities are synchronised with different ratios. Their “birefringence”, quantified by FSR of the laser cavity, is a geometrical feature of the cavity and sets both a different carrier envelope offset (CEO) and lasing threshold for the two groups of modes. The two fields then have an effective opposite parity, i.e., a shift of π, thus realizing the Möbius topology.