Concentration dependence of amplified spontaneous emission in two oligo-( p -phenylenevinylene) derivatives

Amplified spontaneous emission (ASE) in optically pumped polystyrene (PS) films doped with two different oligo-( p -phenylenevinylene) derivatives (OPVs), with three (3-OPV) and five (5-OPV) monomer units is reported. It is observed that there is a maximum content of oligomer ( 25 wt. % for 3-OPV and 20 wt. % for 5-OPV) that can be introduced in the films, due to degradation (in 3-OPV) and ASE quenching (in 5-OPV). Optimal concentrations (with minimum pump-intensity thresholds for the observation of ASE) of 15 wt. % and 9 wt. % are measured for the trimer and the pentamer, respectively. The concentration dependence of the ASE threshold is discussed in terms of the optical absorption spectra. Gain coefficients are obtained by analyzing the dependence of the ASE with the length of the pump stripe. The results show that films based on 5-OPV appear to be more efficient and stable than those based on 3-OPV.