Excitation Dynamics in Disubstituted Polyacetylene

We studied the excitation dynamics in films of disubstituted polyacetylene, a degenerate ground-state conjugated polymer, using psec transient and steady-state spectroscopies. The polymer is found to support charged and neutral topological soliton excitations concurrent with a strong intrinsic photoluminescence band with quantum efficiency, $\eta \simeq 50\%$. This leads to stimulated emission in thin films and lasing in cylindrical $\mu$ cavities. The seeming contradiction of a degenerate ground-state polymer with high $\eta$ is explained by the lowest excited-state ordering.