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Conjugate Polymers are novel optoelectronic materials with wide range of
applications. In this paper, we present the results of fluorescence and laser excited amplified
emission spectra of MEH-PPV polymer, which has some surprising laser properties.
(MEH -PPV) is a complex macro molecule. When this is dissolved in liquids like,
tetra hydro furan (THF), it is very fluorescent, with quantum yield comparable to
conventional laser dyes. This polymer has absorption peak around 490nm and emission peak
at 560nm for a low concentration (1 micro molar). However for higher concentration (10
micro molar) it has a new band at 600nm, in emission only without any new band in
absorption. This is a strong indication of excimer formation.
When this particular solution is pumped by a 3rd harmonic of Nd-YAG laser (355nm
and 11 ns), the polymer underwent strong excitation and population inversion and amplified
spontaneous emission (ASE) at 600 nm only. For lower concentration, we could get
fluorescence only with a peak at 560 nm. That is, this particular polymer produces ASE and
hence laser only from the excimeric state. It is important note that most of the liquid laser
dyes do not produce laser from the excimeric state; other solutions which are easily
forming excimeric state do not laze. This appears to be the only liquid excimeric state laser.
Another important feature of the solution it is at least 10 times more stable than the
conventional laser dyes.
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