THE ROLE OF AMPLIFIED SPONTANEOUS EMISSION IN THE ULTRAFAST RELAXATION DYNAMICS OF POLYMER-FILMS

We show that gain relaxation dynamics in thin films of methyl-substitu ted poly-(para-phenylene)-type ladder polymer, investigated by femtose cond pump-probe spectroscopy under high excitation fluence, is affecte d by amplified spontaneous emission (ASE), which provides for an effic ient excited state population depletion mechanism. The ASE influence o n the photoluminescence spectral narrowing is also investigated. A gen eral model which accounts for both excited state population dynamics a nd photoluminescence spectral evolution is presented. (C) 1998 Elsevie r Science B.V. All rights reserved.