Light-Driven Femtosecond Electricity

Scientists in Canada foresee the use of electromagnetic fields of laser light for inducing and reversing tiny electrical currents along molecular wires without the use of a voltage applied across leads. They would accomplish this feat by shining special laser pulses containing light waves at two different frequencies onto a polyacetylene molecule which acts like a junction between two metallic leads on either side (see figure at http://www.aip.org/png/2007/286.htm).

Depending on the exact frequencies used, the time duration of the pulse, and the relative phase relation between the two components of light, the induced pulse of electric flow could consist of as little as a single electron or many.

For the case of one electron set in motion by the 400-femtosecond pulse of laser light the resulting electrical “current” would be about 0.4 microamps. Why use light rather than voltage to drive electricity? Because the whole thing can be done on a femtosecond scale with lasers.

Ignacio Franco (ifranco@chem.utoronto.ca, 416-978-4422) says that a potential use of laser-driven electricity would be in future optoelectronic devices such as ultrafast nanoswitches. (Franco, Shapiro and Brumer, Physical Review Letters, upcoming article