Fast and ultrafast response of aligned organic nanofibers - Towards organic nanolasers

Systematic investigations of luminescence lifetimes of organic phenylene nanofibers are presented as a function of intrinsic parameters such as morphology or bleaching factor as well as extrinsic parameters such as substrate material, coating or excitation intensity. By varying either one of these parameters, the decay times of the electronic excitation can be varied. This should have a (strong influence on the efficiency of nanolasing, which is observed by increasing the excitation intensity of a femtosecond pump laser. Lasing action starts at pump fluences as low as a few μJ/cm2 per pulse. In ensemble measurements, the number of lasing modes depends strongly on the density of contributing nanofibers. In spatially resolved measurements, the nonlinear optical response of individual nanofibers is investigated. This enables us to make a correlation between the morphological features of the nanofibers. as deduced from atomic-force microscopy, and their lasing properties.