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An all-optical switch on silicon

A photonic circuit in which one light beam controls the flow of another beam is a longstanding goal for developing highly integrated optical communication components. For optimal integration, it is highly desirable to use silicon - the dominant material in the microelectronics industry - as a platform for photonic chips. CNS researchers have obtained the first experimental results of all-optical switching on silicon by using a highly confining nanostructure [see Fig. below] to enhance the sensitivity of light to optically-induced refractive index changes and to minimize thermal effects. Under optical excitation, the structure can be made to be almost completely opaque or transparent, acting as an all-optical gate. The transmission of the structure can be modulated or switched by more than 97% in less than 500 ps (half a billionth of a second) using light pulses with energies as low as 40 pJ (0.04 billionths of a Joule)

Scanning electron microscope image that shows the top-view of a ring resonator coupled to a waveguide. Inset shows the entire ring structure . A pump pulse incident on the ring structure controls the transmission properties of a signal pulse sent through the waveguide (straight feature).

[ Lead CNS Investigators: M. Lipson and A. L. Gaeta ]

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