Amplified spontaneous emission in optically pumped neat films of a polyfluorene derivative

We report the emissive properties of a fluorene-based polymer, PF-1SOR, in planar asymmetric waveguides under optical pumping. A laser beam homogenizer setup was applied to achieve the flat-top intensity profile of the excitation light. Amplification of deep blue light via stimulated emission (SE) occurred at an energy threshold of 11 μJ cm−2 and the amplified spontaneous emission (ASE) peak could be tuned from 411 to 423 nm. A net gain coefficient of 19.8 cm−1 was obtained by means of the modified variable stripe length (VSL) method. The PF-1SOR thin films delivered a remarkably low loss coefficient of 1.5 cm−1, among the lowest ever reported for a single component polymer waveguide.