A simple approach to transient-gain measurements in neat polymer films

Summary from only given. We have developed a simple transient-gain technique with the aim of measuring the decay time of the gain at the peak of the spectral gain curve. To do so we excite the neat polymer film across a pencil-shaped region 2 mm long with a femtosecond pulse at such a power level that the spontaneous emission along the stripe gets weakly amplified. After some delay we reexcite this stripe with an equally strong probe pulse of exactly the same spatial and temporal profile. We measure the time-integrated signal emitted by the stripe upon this dual-pulse excitation as a function of the interpulse delay.