Dynamics of photoexcitation and stimulated optical emission in conjugated polymers: A multiscale quantum-chemistry and Maxwell-Bloch-equations approach

We present a general microscopic theory of intense optical pulse propagation in conjugated polymers. The multiscale theory is based on a combination of density-functional theory on the molecular level and many-particle vibronic density matrices which act as a source in Maxwell's equations. The resulting equations are solved nonperturbatively in the light field to study optical amplification and lasing. We illustrate our approach using a polyfluorene material of particular current interest containing a small component of planar (beta-phase) chromophores. Significant reshaping of amplified light pulses is found, stemming from the interplay between light propagation and the excitation of numerous vibrational modes. Furthermore a rich dynamic is observed in the amplified spontaneous emission regime with oscillatory structures rooted in the dynamical population and depopulation of lattice modes.