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Ultra-Broad Optical Amplification and Two-Colour Amplified Spontaneous Emission in Binary Blends of Insulated Molecular Wires

Sergio Brovelli, Tersilla Virgili, Marta M. Mroz, Giuseppe Sforazzini, Alberto Paleari, Harry L. Anderson, Guglielmo Lanzani and Franco Cacialli, Weinheim (2010)

The ability to produce polymeric materials with broad optical gain spectra and large stimulated emission cross sections is fundamental to their use as active gain media in all-plastic lasers, optical switches and broadband amplifiers. Supramolecular encapsulation of conjugated polymers is an effective means of suppressing intermolecular interactions, which leads to enhanced luminescence quantum yields, blue shifted emission, and to suppression of long-lived excited states. Furthermore, energy transfer (ET) in resonant blends of encapsulated conjugated polymers is effectively hindered, and results in simultaneous exploitation of the optical properties of the individual blend components. Here, we show that all such properties of conjugated polyrotaxanes combine into a high impact photonic application: ultra-broad band optical gain in a binary polymer blend that can be further exploited for two-colour lasing. We study the ultrafast optical properties of a binary blend of a green-emitting polyfluorene copolymer and a polyrotaxane consisting of a polyfluorene derivative threaded into functionalized β cyclodextrin macrocycles, by means of femtosecond transient absorption experiments and amplified spontaneous emission (ASE) measurements. The morphology of the blend is also investigated by microRaman imaging. We ascribe the ultra-broad optical gain spectrum (>850 meV), and the concomitant ASE for both blends constituents, to the dual effect of reduced polaron formation and suppressed energy transfer in our polyrotaxanes-based blends.

Partners : UCL

Place of Publication : Weinheim

Date of Publication : 2010/06/29

Additional Data : Adv. Mater. 2010, 22, 3690–3694

Link to the online version of the article.