An optically pumped waveguide structure has been fabricated with methyl substituted conjugated laddertype poly(paraphenylene) as the active material. The choice of the device parameters allows one to observe a high directionality, a small beam divergence, a complete linear polarization, and a linewidth with an upper limit of 1.7 nm at a considerable low threshold of 3 kW/cm2 at room temperature.

We present femtosecond pump-probe measurements, both conventional and electric field-assisted, on organic light-emitting devices based on para-hexaphenyl. The dominant triplet exciton generation mechanism is assigned to nongeminate bimolecular recombination of photogenerated, spin-1 2 polarons. This process is active within a few hundred femtoseconds after photoexcitation and involves about 20% of the initially excited states. At higher photoexcitation densities, we observe an additional triplet generation mechanism, which occurs in the 10-ps time domain, due to fusion of singlet excitons and subsequent fission into correlated triplet pairs. The latter decay on the 10 2 -ps time scale by geminate recombination. ͓S0163-1829͑99͒01721-X͔

We demonstrate single-mode laser emission at 490 nm from a stable cavity based on a methyl-substituted poly-(para-phenylene)-type ladder polymer. The laser emission is characterized by a well-defined excitation fluence threshold, a high directionality, and a drastic spectral narrowing. The laser generates picosecond pulses of excellent amplitude stability.

We report on a comprehensive characterization of the ultrafast emission processes in films of methylsubstituted poly͑para-phenylene͒-type ladder polymer, by femtosecond frequency up-conversion and pumpprobe spectroscopy. We found that bimolecular recombination mechanisms mainly govern the ultrafast emission processes, at high excitation fluences, in films with thickness well below cutoff for waveguiding of the emitted light. Amplified spontaneous emission strongly affects emission processes ͑spectral narrowing, luminescence and gain temporal dynamics͒ in films with superior optical confinement properties.

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