16 December 1998 Gain mechanisms in conjugated polymer lasers
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We report on a tunable laser based on a conjugated polymer blend system and investigate the underlying gain mechanism. A solid polymer blend consisting of the conjugated polymer poly(phenyl-p-phenylenevinyene) dispersed into an inert matrix of polymethylmetacrylat is examined. Emission line narrowing which can be attributed to amplified spontaneous emission (ASE) is observed at high excitation densities. Placing a block of the blend system into an external resonator yields true laser emission. Emission linewidth and peak intensity show a clear threshold behavior. The laser emission is highly collimated, coherent, and highly polarized. It can be tuned over a range of 300 meV. Gain spectra indicate that the gain mechanism can be explained within the molecular model for conjugated polymers in close analogy to the gain mechanism well known from dye lasers. Thin films of a methyl-substituted ladder-type poly(p- phenylene) are examined to check if the result obtained from a diluted system also hold for neat films. ASE is observed upon increasing the pump intensity. Additionally, quasi- resonant, spectrally very narrow emission lines can be observed. These emission lines are energetically offset from the excitation laser by energies corresponding to well known molecular vibrations. This confirms the previous assumption that the gain mechanism in conjugated polymers is linked to molecularly excited states.
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Georg Wegmann, Georg Wegmann, B. Schweitzer, B. Schweitzer, Harald W. Giessen, Harald W. Giessen, Rainer Friedbert Mahrt, Rainer Friedbert Mahrt, "Gain mechanisms in conjugated polymer lasers", Proc. SPIE 3476, Organic Light-Emitting Materials and Devices II, (16 December 1998); doi: 10.1117/12.332625; https://doi.org/10.1117/12.332625

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