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Proceedings Paper

Optical gain in Coumarin 545T-doped Tris(8-hydroxy-chinolinato)aluminium thin films
Author(s): T. Rabe; P. Görrn; T. Riedl; W. Kowalsky
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Paper Abstract

In this paper we investigate the optical gain in organic thin film waveguides using the variable stripe length method (VSL). As active medium the guest-host system containing Tris-(8-hydroxy-chinolinato)-aluminium (Alq3) doped by 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H- (1)-benzopyropyrano- (6,7-8-i,j)quinolizin-11-one (C545T) is studied. The doping concentration is varied over a wide range and the gain coefficient is measured at different excitation densities to analyze the behavior of the differential gain. The F¨orster energy transfer is responsible for the occupation of the exited state of the coumarin molecules. For low doping concentrations with an inefficient host-guest energy transfer a low stimulated cross section can be observed. At optimal doping concentrations (3.7-6.4 wt%) we obtain a cross section of σ =6.8x10-17 cm2 and a high material gain of gmat ≈500 cm-1 at an excitation density Eex of Eex ≈300 μJ/cm2. A further increased doping concentration (15 wt%) leads to a reduced cross section, due the onset of concentration quenching in the guest-host system. Furthermore, at high excitation densities we observe a strong saturation effect of the maximum gain which depends strongly on the doping concentration.

Paper Details

Date Published: 16 October 2007
PDF: 7 pages
Proc. SPIE 6655, Organic Light Emitting Materials and Devices XI, 66551F (16 October 2007); doi: 10.1117/12.733875
Show Author Affiliations
T. Rabe, Technische Univ. Braunschweig (Germany)
P. Görrn, Technische Univ. Braunschweig (Germany)
T. Riedl, Technische Univ. Braunschweig (Germany)
W. Kowalsky, Technische Univ. Braunschweig (Germany)

Published in SPIE Proceedings Vol. 6655:
Organic Light Emitting Materials and Devices XI
Zakya H. Kafafi; Franky So, Editor(s)

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