The authors study laser dynamics in a polymer distributed feedback resonator by performing pump-probe experiments. They measured the population kinetics in the device under lasing operation with subpicosecond time resolution. By modeling the system with a set of coupled rate equations, which account for stimulated emission and nonradiative decays, they extract quantitative information on buildup time, photon lifetime, and pulse duration and give evidence of the feedback and loss mechanisms. They also investigate the influence of the grating length in the feedback and loss processes, and they show that lower pump energy thresholds can be achieved with short devices. (c) 2006 American Institute of Physics.