Spectral effects of gain saturation in the β-phase of poly(9,9-dioctylfluorene)

Anni, M.; Alemanno, M.
September 2008
Applied Physics Letters;9/22/2008, Vol. 93 Issue 12, p123311
Academic Journal
We investigated the amplified spontaneous emission (ASE) properties of the β-phase of poly(9,9-dioctylfluorene) at T=5 K. We observe ASE at about 478 nm with a threshold as low as 50 μJ cm-2. For excitation density higher than 350 μJ cm-2 a clear spectral rebroadening and a progressive ASE intensity saturation, ascribed to gain saturation, are observed. The gain saturation at 478 nm leads to ASE from the 470 nm vibronic band, with a threshold of about 3.0 mJ cm-2. We show that these effects are due to the break down, at high excitation density, of the four level amplifier scheme, typically applied to conjugated polymer films.


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