Physicists at the University of Michigan have created a semiconductor device capable of controlling electron movement through laser light alone, without relying on applied electric fields or electrical power. The breakthrough emerged from fundamental research into quantum physics phenomena and could eventually support technologies combining optics and electronics, including enhanced sensing systems, imaging applications, and telecommunications infrastructure.
The research team, supported by grants from the U.S. National Science Foundation, demonstrated that two distinct colors of light could generate organized electron flow through a semiconductor material. By adjusting the polarization of the two optical fields—essentially changing the direction light waves oscillate—the researchers could alter the direction of the resulting current. According to Steven Cundiff, the senior physicist on the project, this represents a fundamentally different mechanism from conventional electron movement, where electrons typically require an applied electric field to drift through materials. The new approach allows light to direct electrons in specific directions without any electrical field present.
The device functions through quantum interference, a phenomenon where two colors of light simultaneously send the semiconductor through different absorption pathways that converge at the same endpoint. The process occurs when photons, discrete energy packets from the light, mobilize the charge carriers within the semiconductor. The interference pattern created resembles overlapping ripples in water—for electrons moving in one direction, the ripples align and strengthen each other, while in other directions they cancel out. This selective reinforcement concentrates the electron current in a particular direction rather than allowing it to spread uniformly throughout the material. Cundiff likened the effect to a lighthouse beam sweeping across the horizon, with the electron stream serving as the rotating light.
The working device realizes a theoretical prediction made earlier by physicist J.E. Sipe of the University of Toronto. Doctoral researcher Yiming Gong transformed the theoretical concept into a functional device with assistance from the Lurie Nanofabrication Facility. A critical challenge involved preventing unwanted electric fields from affecting the results, as researchers needed to confirm that electron movement originated solely from the light source. This required extensive experimentation with different fabrication methods and processing parameters. Gong has since completed his doctorate and transitioned to work in machine learning applications in Chicago.
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