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September 19, 2007

Femtoseconds changes in reflexivity useful for optical switching

In a recent experiment short laser pulses, falling on an organic salt target, momentarily changed the material from an insulator (a bad reflector of light) to a semi-metal (good reflector of light).
The change in reflectivity this large---more than 100%-has never been achieved before in a photonic material; photo-induced changes are usually more like a few percent. The laser pulse required doesn’t even have to be particularly intense to cause the change.

Thus gigantic photo-response work began as a Tokyo-Kyoto collaboration but now includes also LBL and Oxford. The new advance is that the change in reflectivity can be brought about in tens of femtoseconds rather than 150 ns. The dramatic reflectivity changes will be useful in bringing about direct ultrafast optical-to-optical switching.
It could also be useful for faster optical computing.

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