Interfacial Memory States Govern the Predictable Design of Strongly Driven 2 μm Heterostructure Ultrafast Lasers

Strong-field-driven 2 μm heterostructure passively mode-locked ultrafast lasers often exhibit unpredictable operational drift, yet its physical origin remains unclear. Existing theories usually treat nonlinear modulation as a static parameter independent of operational history, leaving out an intrinsic time variable required to describe continuous system evolution. By combining multiphysics thermo-mechanical calculations with cross-scale molecular dynamics simulations, it is shown that the interfacial atomic configuration of the MoS 2 /Ti 3 C 2 T x heterojunction accumulates operational history and undergoes progressive reconstruction under sustained optical-thermal driving. The evolution of local Mo–S, Ti–C, and terminal-group coordination environments further translates this atomic-scale history into a time-varying nonlinear response. Interfacial atomic evolution is therefore identified as an intrinsic time variable of heterostructure ultrafast lasers, while distinct interfacial memory states define a dynamic scale for the system’s dynamical stage and modulation drift. On this basis, a ResNet–MLP predictive framework is established to directly map interfacial atomic states to macroscopic laser output, achieving an R 2 of 0.856 and a minimum relative error of 2.2%. Experimentally, 2 μm passive mode-locking is obtained with a pulse width of 752 ps and a single-pulse energy of 10 nJ. These results establish heat-history-driven interfacial atomic evolution as the physical origin of operational drift in heterostructure ultrafast lasers.