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Gain Dynamics in Conjugated Polymers at Room Temperature
Author(s) -
Spiegelberg Ch.,
Schülzgen A.,
Allemand P. M.,
Kippelen B.,
Peyghambarian N.
Publication year - 1998
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/(sici)1521-3951(199803)206:1<131::aid-pssb131>3.0.co;2-k
Subject(s) - exciton , photoexcitation , femtosecond , relaxation (psychology) , stimulated emission , laser linewidth , materials science , atomic physics , emission spectrum , amplified spontaneous emission , spectral line , population , molecular physics , optical pumping , laser , chemistry , optics , physics , condensed matter physics , excited state , psychology , social psychology , demography , astronomy , sociology
We report on stimulated emission and optical gain in BEH‐PPV polymer films at room temperature. Performing femtosecond pump–probe experiments we find very fast (≤100 fs) relaxation of excitons within a ladder of vibronic states. From spectra taken at very early times after photoexcitation we identify several vibronic transitions with a linewidth of about 8 nm. Strong coupling of excitons to these vibrations leads to stimulated emission and large optical gain of up to 10 4 cm —1 . For a pump–probe delay of 200 fs the different transitions are no longer distinguishable due to broadening through spectral diffusion and exciton migration. The lifetime of the optical gain corresponds to the exciton lifetime. Population depletion by stimulated emission leads to a density dependent decay within a few hundred fs up to about 2 ps.