University of Michigan device steers semiconductor electron current with two laser beams

Researchers at the University of Michigan built a semiconductor device that uses a pair of laser beams to generate and steer an electron current without an external electric field, SciTechDaily reported, based on work in Physical Review Letters. With National Science Foundation support, the team used two colors of light to produce an organized electron flow and changed its direction by rotating the polarization of the two optical fields. Earlier experiments had shown light could generate a current without applied voltage; the new device concentrates electrons into a narrower stream and aims them along a selected path. The effect depends on quantum interference between two optical absorption pathways to the same final state. For electrons traveling in one direction the pathways reinforce; in other directions they cancel. Yiming Gong, then a doctoral student in the U-M Department of Physics, helped lead the project and said the Lurie Nanofabrication Facility device could eventually measure aspects of light. Senior author Steven Cundiff said light no longer merely switches the current on but also aims it. The writeup says the work could support technologies that combine optics and electronics, including sensing, imaging and telecommunications.