Researchers have developed a new semiconductor device that can turn light into a directed flow of electrons without using an external electrical power source.
The work was carried out at the University of Michigan and published in Physical Review Letters. The device uses two laser beams of different colors to generate and steer an electronic current inside a semiconductor.
Normally, electrons move through a material when an electric field is applied. In this new system, however, the electrons are pushed in a specific direction by light alone. This makes the device an important demonstration of how optical signals can directly control electronic motion.
The researchers used two phase-coherent optical fields, meaning the light waves were carefully synchronized. By changing the polarization of the laser beams, they could control the direction in which the electron current moved.
This effect is described as an โelectron lighthouse.โ Just as a lighthouse sweeps a beam of light across the horizon, the device can sweep a beam of electrons through different directions by adjusting the light.
The underlying process depends on quantum interference. In the semiconductor, the two colors of light create different absorption pathways that lead to the same final state. For electrons moving in one direction, the quantum pathways reinforce each other. For electrons moving in other directions, they cancel out.
As a result, the light does not simply create a current; it also aims the current.
Earlier studies had shown that light could generate electron movement without an applied electric field. This new work goes further by concentrating the electrons into a narrow stream and directing that stream along a chosen path.
The device was fabricated at the Lurie Nanofabrication Facility. Creating it required careful control of the materials to avoid unwanted electric fields that could interfere with the experiment.
The discovery could support future technologies that combine optics and electronics. Possible applications include sensing, imaging, telecommunications, and advanced signal processing.
By allowing light to control both the generation and direction of electronic current, the device opens a new route for faster and more information-rich optoelectronic systems.
Journal Reference:
Gong, Y., Wang, K., & Cundiff, S. T. (2026). Directional Photocurrent Generated by Quantum Interference Control. Physical Review Letters. https://doi.org/10.1103/3v91-5pzf