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A detailed analysis of the optical waveguide modes in organic light emitting diodes (OLEDs) is presented. The modes are compared with respect to their electric field profile, attenuation coefficient and optical confinement factor. The first transversal electric (TE) mode is best suited for an optimized energy transfer from emitting dipoles. The transversal magnetic (TM) modes are characterized by a large plasmon character with high absorption. The propagation constants of distinct modes have been measured in test devices by grating coupling. [Copyright &y& Elsevier]

We present measurements of amplified spontaneous emission (ASE) in films of spiro-sexiphenyl and higher branched spiro starburst compounds of the 1st and 2nd generation. Gain narrowing is observed at threshold intensities of approximately 3.2 μJ/cm2 when pumped with 500 ps pulses at 337 nm. A comparison of ASE peak wavelengths, linewidths and degradation kinetics in air is presented for the different spiro compounds. The ASE lines are the 1-0 fluorescence transitions of the three compounds at 419, 428 and 443 nm, respectively, with linewidths of approximately 3 nm. The dependence of ASE threshold on film thickness is explained in terms of waveguide optics. The lowest threshold is achieved for monomode films (100–150 nm). Photo-degradation effects occur in air atmospheres but can be suppressed in oxygen-free environments. [Copyright &y& Elsevier]