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Organic dopants for Plastic Optical Fibres exhibiting gain and ultrafast optical switching

Mendonça, A. ; Charas, A. ; Clark, J. C. ; Gonzalez, J. C.-G. ; Bazzana, L. B. ; Nocivelli, A. N. ; Lanzani, G. L. ; Morgado, J.

Organic dopants for Plastic Optical Fibres exhibiting gain and ultrafast optical switching, Proc RIAO/OPTILAS, Porto, Portugal, Vol. -, pp. - - -, July, 2013.

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Abstract
Plastic optical fibres (POFs), such as those based on polymethylmethacrylate (PMMA), possess larger cores than those based on silica, which facilitates their interconnection, and are more flexible. However, their high losses, mostly related to CH vibration overtones absorption, limit their use to very short/local distances. It has been shown that POFs based on polymers where hydrogen has been replaced by fluorine (such as CYTOP) show even lower losses than the silica ones, over limited spectral range. However, their high cost does not allow their wide use.
The alternative that we have explored in this work is the incorporation of dopants in PMMA that can provide gain, thereby compensating for its higher loss. The dopants are conjugated/semiconducting polymers and oligomers that exhibit amplified spontaneous emission in the visible range. The challenges here rely on the search for the best dopant, in terms of i) amplification efficiency; ii) thermal and photostability, and iii) high miscibility with PMMA, in order to achieve high dopant loads. These dopants were also shown to exhibit ultrafast optical switching, which could be used to modulate the propagating signals. In this presentation we will present the various dopants that we have synthesised and the performance of films and POFs based on such doped PMMA materials in relation with dopants molecular structure. Pump-probe and pump-push-probe studies were carried out, both in solution and in solid state, to characterise their stimulated emission and optical switching. The attenuation of POFs drawn from some of these materials was also determined.