Ultrafast dynamics of reconfigurable mode switching of polariton condensates revealed in a tunable ZnO microcavity

Mode switching in exciton-polariton condensates represents a significant phenomenon that illustrates the non-Hermitian properties and out-of-equilibrium dynamics of exciton-polaritons. In this research, we experimentally demonstrate controllable mode switching in a tunable ZnO microrod cavity at room temperature, where increasing pump power drives the condensate from one lower polariton branch to another of higher energy. This unconventional up-switching is explained by an imbalance in the densities of the active excitonic reservoirs, governed by both loss and relaxation efficiency. Ultrafast spectroscopy reveals a several-picosecond delay between the condensates, providing direct evidence for this mechanism. Our results provide important insights into the fundamental physics of Bose-Einstein condensation in dissipative systems, enable control of polariton condensation through reservoir engineering, and open routes to room-temperature polaritonic devices exploiting nonlinear switching.