Tuneability of the ASE in thin organic films

We show that the amplified spontaneous emission (ASE) in poly[2-methoxy, 5- (2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) can be tuned by contr olling the film thickness and the excitation intensity, For sufficiently th in films the peak position of the ASE is determined by the cut-off waveleng th for the waveguide and is shifted to shorter wavelengths with decreasing film thickness. Increasing excitation intensity causes a blue-shift of the emission spectra, We also show that excitation wavelength has no effect on the position of the ASE.