Fluorene-based conjugated polymer optical gain media

We report a detailed investigation of the optical gain properties of a series of semiconducting polyfluorenes with photoluminescence emission spectra that span the entire visible spectrum. Stimulated emission was demonstrated at low pump pulse energies (greater than or equal to 0.1 muJ for 10 ns, 10 Hz pulses) in the blue, green and red parts of the spectrum via amplified spontaneous emission (ASE) measurements on asymmetric slab waveguides. These structures exhibit large net gains g less than or equal to 74 cm(-1), and corresponding gain cross-sections sigma greater than or equal to 7 x 10(-16) cm(2), together with very low loss coefficients, alpha greater than or equal to 3.2 cm(-1). The spectral location of the maximum waveguide amplification can be widely tuned (Deltalambda greater than or equal to 30 nm) by controlling the allowed propagating modes or by blending the active emitter with a second larger optical gap polyfluorene. Our results confirm that fluorene-based polymers are attractive gain media for use in highly tuneable solid-state polymer lasers and amplifiers. (C) 2003 Elsevier B.V. All rights reserved.