Amplified spontaneous emission (ASE) from optically pumped thin film wave guides of a fluorene-based copolymer, poly(2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl )imino)-1,4-phenylene)) (TFB), which has a high hole mobility and a low ionization potential in comparison with those of fluorene-based copolymers, has been observed. The net gain spectra and the loss coefficient of TFB wave guides are measured as gain media for use in solid-state organic lasers. A maximum net gain of 15.5 cm(-1) and a low loss coefficient of 12.1 cm(-1) are obtained at the ASE wavelength of 459 nm. (c) 2004 Elsevier B.V. All rights reserved.