Dissipative solitons in parity-time symmetric laser cavities

Abstract: The generation of optically coherent ultrashort pulses by mode-locked lasers has revolutionized advancements in modern science and technology. These pulses often arise from the formation of dissipative solitons, which emerge due to a balance between energy excitation and dissipation. Harnessing the concept of parity-time (PT) symmetry to control this balance, we demonstrate a new type of laser dissipative solitons hosted in linearly coupled ring cavities. Our experiments are performed in a laser where the linear hybridized modes are in the PT-symmetric phase. We experimentally observe the formation of short pulses, stabilized by the selective breaking of the PT-symmetry by the Kerr nonlinearity. Our results unlock new possibilities for passive mode-locking by showing spontaneous pulse formation in PT-symmetric lasers without the need for additional intricate components such as saturable absorber or non-reciprocal and polarisation sensitive elements.