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Summary form only given. Electroluminescence from conjugated polymers has opened new doors for the application of organic materials in electrically pumped light-emitting devices. Because photoluminescence line narrowing and stimulated emission in a variety of conjugated polymers have been reported recently, the prospects of electrically pumped polymer lasers are exciting. As the active material, we use the semiconducting conjugated polymer BEH:PPV [poly-2,5-bis(2'-ethylhexyloxy)-1,4-phenylenevenylene]. For laser applications, the active material has to be combined with an optical feedback structure. To form a high quality planar cavity, we use a pair of dielectric mirrors that contain a stack of alternating quarter-wave layers of low and high refractive-index materials. The mirrors are characterized by low losses and high reflectivities in the gain region of the polymer. A 200-nm film of BEH:PPV is spin-coated onto one of the dielectric mirrors. We excite with 100-fs optical pulses into the /spl pi/-/spl pi/* absorption band of BEH:PPV (555 nm). we compare the emission spectra from the polymer in the cavity with the emission of a single BEH:PPV layer without a cavity for three pump intensities. For all these intensities, the excitation is high enough to obtain optical gain and stimulated emission in the polymer layer. The emission spectrum of the polymer layer without cavity shows a narrow emission band that is typical for excitation above the threshold for stimulated emission.