20 April 2006 Amplified spontaneous emission in TPD-based waveguides: thickness and TPD concentration dependence.
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The concentration dependence of amplified spontaneous emission (ASE) in optically pumped polystyrene (PS) films containing a variable concentration (between 2.5 and 100 % by weight (wt)) of the luminescent and hole-transporting organic molecule N,N'-Bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD) is studied. It is observed that the photoluminiscence (PL) efficiency, the ASE threshold and the linewidth above threshold, decrease with concentration up to 20 wt % doped films and then keeps a constant value up to concentrations of 100 wt % (neat films). The position of ASE can be tuned between 413nm and 421 nm by changing the concentration of TPD. It was also possible to tune the ASE position (between 404 and 417 nm) trough control of the film thickness (between 100 and 200 nm). The observed shifts of the ASE position due to changes in concentration are determined by the PL efficiency (not by the waveguiding characteristics of the films). On the other hand, the observed shifts in the ASE position due to changes in film thickness depend on the shape of the PL spectrum and on cut-off thickness limitations. In this case, the ASE thresholds depend on the different confinement of the propagation modes due to thickness variations.
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Eva M. Calzado, Eva M. Calzado, José M. Villalvilla, José M. Villalvilla, Pedro G. Boj, Pedro G. Boj, José A. Quintana, José A. Quintana, María A. Díaz-García, María A. Díaz-García, } "Amplified spontaneous emission in TPD-based waveguides: thickness and TPD concentration dependence.", Proc. SPIE 6192, Organic Optoelectronics and Photonics II, 619231 (20 April 2006); doi: 10.1117/12.663067; https://doi.org/10.1117/12.663067

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