Conjugated polymer lasers: emission characteristics and gain mechanism

The photoluminescence emission from a conjugated polymer blend system is investigated. Line narrowing which can be attributed to amplified spontaneous emission (ASE) is observed upon increasing the excitation density. Pump-probe experiments reveal a spectrally broad positive gain, supporting this notion. The gain dynamics are investigated on a picosecond timescale. A laser based on the polymer blend system is realized by placing the material into an external resonator. The laser emission is characterized with respect to its coherence, tunability and polarization. The dependence of the laser emission on pump polarization and pump wavelength gives insight into the nature and the dynamics of the excited states involved in the lasing process. A model for the gain mechanism in conjugated polymer lasers is proposed based on our measurements.