Ultrafast resonant optical switching in organic materials doped in matrix

In the last few years there has been a resurge in interest in the use of organic materials for photonics-based applications. This is due to the now pressing demand for broad-band communication, the achievement of laser amplification and lasing based on polymers, and the growing potential of plastic optical fibers. Here we report achievement of broad-band gain, and optical switching investigated by ultrafast spectroscopy. We study two different oligofluorenes in comparison with poly(9,9, dioctylfluorene), a commonly used polymer, all of them dispersed in a poly(methylmethacrylate) (PMMA) matrix. For all compounds investigated we find an enlargement of the stimulated emission band in the visible region of at least 80 nm respect to the pure solid state film. We assign this gain enlargement to reduced or suppressed inter-chain interaction. Using a three pulse experiment (pump-push-probe) we provide evidence of charge generation from higher lying states. Furthermore, making use of the fact that the photoinduced absorption band of charged polarons overlaps in part with the gain region, we report an ultrafast optical gain switching in the stimulated emission (SE) region. This region extends over a broad wavelength range (- 100 nm). Our experiments suggest that the expected maximum rate of on-off switching in such a molecular device can be as high as 300 GHz. Copyright © 2007 Materials Research Society.