Low-threshold amplified spontaneous emission and laser emission in a polyfluorene derivative

The amplified spontaneous emission (ASE) and lasing properties of a fluorene copolymer PF(3)Cz film waveguide were investigated under optical pumping. Low ASE and lasing threshold were observed at 59 W/cm(2)/pulse and 1.7 KW/cm(2)/pulse, respectively. The stimulated emission cross section of the PF(3)Cz film was estimated to be approximately 1.6x10(-16) cm(2) at the ASE peak of 448 nm. The absorption cross section was estimated to be 2.8x10(-16) cm(2) at the absorption peak lambda=370 nm. Gain and loss measurements at the ASE peak showed that the net gain coefficient reaches 26+/-1.7 cm(-1) when pumped at 1.4 KW/cm(2), and the loss coefficient of the waveguide was about 13+/-1.1 cm(-1).