Dissipative soliton molecules in active random metamaterials

Self-organization of radiation in random media is a key to controlling the optical energy flow and constitutes the basis of innovative cavity-free laser designs. Here, we theoretically demonstrate the existence of robust temporal dissipative soliton molecules in a graphene-based active disordered metamaterial. We observe that localized pulses with single and multiple peaks can coexist inside this metamaterial for a wide range of gain parameters, thereby exhibiting optical bistability. We further investigate the stability of such bound states under perturbation by analyzing their interaction force, finding stable tri-soliton molecule states with a periodically oscillating relative phase and a stable bi-soliton molecule. Our results offer a paradigm for mode-locking in active random metamaterials and pave the way for versatile applications such as multilevel encoding in optical communications, future designs of low-cost cavity-free lasers, and optical amplifiers.