Travelling-wave lasing of triphenylamine-based poly(phenylene vinylene)

Travelling-wave lasing (amplified spontaneous emission) is reported for a s eries of triphenylamine-based poly(phenylene vinylene)copolymers (TPA-PPVs) that have different substituents R at the vinylene double bond (R=H, CN, m ethoxyphenyl) and slight modifications in the alkoxy side chains (dioctyl, MEH). Wave-guiding neat films on glass substrates are transversally pumped with picosecond laser pulses (wavelength 347.15 nm, duration 35 ps). The la ser emission occurs in the wavelength region between 515 and 560 run. Optic al parameters (refractive index spectra and absorption coefficient spectra) and spectroscopic parameters (absorption cross-section and stimulated emis sion cross-section spectra, fluorescence quantum distributions, internal fl uorescence quantum yields, and fluorescence lifetimes) of the polymers are determined. The lumophore size is extracted from fluorescence lifetime and fluorescence quantum yield measurement and found to be approximately one re peat-unit. The lasing is characterised by measuring the spectral narrowing, the temporal shortening, the laser output energy versus input pump pulse e nergy, and the effective length of amplification. The obtained lasing param eters compare favourably well with those of previously studied MEH-PPV and TPD-PPVs. The laser threshold pump pulse energies are < 650 nJ. The effecti ve lengths of amplification are about I mm. The spectral widths of emission are <9 nm. (C) 2001 Elsevier Science B.V. All rights reserved.