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

Abstract

Travelling-wave lasing (amplified spontaneous emission) is reported for a series of triphenylamine-based poly(phenylene vinylene)-copolymers (TPA-PPVs) that have different substituents R at the vinylene double bond (R=H, CN, methoxyphenyl) 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 347.15nm, duration 35ps). The laser emission occurs in the wavelength region between 515 and 560nm. Optical parameters (refractive index spectra and absorption coefficient spectra) and spectroscopic parameters (absorption cross-section and stimulated emission cross-section spectra, fluorescence quantum distributions, internal fluorescence 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 repeat-unit. The lasing is characterised by measuring the spectral narrowing, the temporal shortening, the laser output energy versus input pump pulse energy, and the effective length of amplification. The obtained lasing parameters compare favourably well with those of previously studied MEH-PPV and TPD-PPVs. The laser threshold pump pulse energies are <650nJ. The effective lengths of amplification are about 1mm. The spectral widths of emission are <9nm.