A novel system for the modulation of amplified emission based on a polyfluorene/diarylethene (namely F8BT/DTP) blend is shown. The high sensitivity of amplified spontaneous emission (ASE) is exploited to achieve efficient emission modulation with a low-intensity control signal. Modulation is then characterized by photoluminescence (PL) lifetime measurements, photocurrent experiments, and density functional theory calculations. This system can also act as a photocurrent switch based on the same principle. This technique may represent a useful tool for fluorescence quenching and sensing as well as find application in organic photonics.