Just as traffic signals keep people from driving (and crashing) their cars on the wrong side of the road, a new waveguide device developed by a Caltech-UC San Diego research team creates a way to keep light signals on a silicon chip from 
reflecting backwards and interfering with its operation.
The breakthrough, published Aug. 5 in the journal Science, clears a major obstacle in photonic chip development. Photonic chips could replace electronic chips as the backbone of information technology and usher in a new era of information sharing that will be faster, more energy-efficient and a lot less expensive than today’s networked computing. How fast? UC San Diego alumnus Liang Feng, lead author on the paper, told the North County Times today that photonic chips will enable Google searches in the blink of an eye instead of the several seconds it requires now.
Thanks to a unique capacity for combining near-field imaging and heterodyne interferometry in the Department of Electrical and Computer Engineering at UC San Diego, grad student Maurice Ayache was able to measure how the light traveled through the waveguide device, proving the system keeps light beams moving in the right direction. The top image shows that the light moves symmetrically going in one direction, while the bottom image shows how the light moves differently – avoiding interference -- when it reflects backwards.
