Ultrafast light-emission processes in poly( para -phenylene)-type ladder polymer films

We report on a comprehensive characterization of the ultrafast emission processes in films of methyl-substituted poly(para-phenylene)-type ladder polymer, by femtosecond frequency up-conversion and pump-probe spectroscopy. We found that bimolecular recombination mechanisms mainly govern the ultrafast emission processes, at high excitation fluences, in films with thickness well below cutoff for waveguiding of the emitted light. Amplified spontaneous emission strongly affects emission processes (spectral narrowing, luminescence and gain temporal dynamics) in films with superior optical confinement properties.