Applied Physics

A Better Optical Switch

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Science  17 Nov 2000:
Vol. 290, Issue 5495, pp. 1261
DOI: 10.1126/science.290.5495.1261a

One of the limiting parameters in optical communication is the rate at which light pulses can be manipulated or gated. At present, all-optical switching technology, in which a control light pulse is used to gate a signal pulse, can offer response times of several hundreds of femtoseconds with a switching energy typically of tens of picojoules. However, the relatively low on-off ratio, around 14 decibels (dB), may compromise the ability to send the information reliably.

Takahashi et al. describe a scheme in which this on-off ratio can be enhanced significantly to about 40 dB for similar switching energies and response times. They exploit the spin-polarized state of a non-linear optical material, a multiple quantum-well, induced by a circularly polarized pump beam. When a linearly polarized signal beam, composed of right- and left-handed circularly polarized light, is reflected off a region of the material, only the component with the same polarization state as the pump beam experiences the refractive index change, thus allowing just one component to be reflected. — ISO

Appl. Phys. Lett. 77, 2958 (2000).

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