Ultrafast gain and excited-state absorption in luminescent polymers: pump-wavelength invariance

We report ultrafast pump-and-probe results for solutions and films of luminescent conjugated polymers. Both photoinduced absorption (PA) and stimulated emission (SE) features were recorded in the excited-state spectrum. The time evolution of the photoexcitations responsible for SE and PA were monitored as a function of the pump wavelength. We find that the PA and SE spectral features and decay dynamics of the excited state are independent of the pump wavelength. This insensitivity to pump wavelength is important for polymer-based photonic applications such as photopumped lasers and ultrafast holographic switches.