A device that controls light so that it travels in just one direction could be used in high-speed computers that carry signals using light, rather than electric charges.
A team led by Lan Yang and Şahin Kaya Özdemir at Washington University in St. Louis created a diode using two doughnut-shaped rings on a silicon chip. While one ring absorbs an incoming light signal, the other amplifies it. When the rings are close together, light travels through the device both ways. When the rings are farther apart, the signal can be amplified in one direction but blocked in the other.
The device is smaller and uses less power than existing optical diodes.
Nature Phys. http://doi.org/r8n (2014)
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Light goes one way on a chip. Nature 508, 290 (2014). https://doi.org/10.1038/508290b