No turning back for light

Nature : Optical computer chips carry information via light rather than electrical current and transfer data at about 10 gigabits per second, which is more than 100 times faster than the best electronic chips. However, to be commercially viable, optical chips need their own equivalent of the electronic diode, which allows current to pass in only one direction and prevents back-scattered current from interfering with the signal. The “optical diodes” created in the past either used materials incompatible with silicon or relied on magnetic fields to block backward-moving light—which made them unusable in computers using silicon chips and magnetic drives. Liang Feng of Caltech and colleagues have created a silicon waveguide that channels light in one direction. Standard waveguides allow passage in both directions, but Feng and his team used simulations to find the right materials and pattern that would allow a lightwave to progress forward while disrupting the backward wave. Their next step is to incorporate the waveguide into a device that filters out backward wave, which Feng and his team hope to complete soon, but it could take as long as 15 years for a full range of optical components to be developed and integrated for commercial use.