Scientists Create ‘Electron Lighthouse’ Using Laser Light

Researchers at the University of Michigan have developed a semiconductor device that uses laser light to direct the movement of electrons without requiring an applied electric field or electrical power source. According to the research team, the system produces a narrow stream of electrons and controls the precise direction of travel through quantum interference, opening potential pathways for advanced optical and electronic technologies.

Two Colors of Light Direct Electron Flow Without External Voltage

The device demonstrates that two different colors of light can produce an organized flow of electrons through a semiconductor material, according to findings published in the journal Physical Review Letters. By rotating the polarization of the two optical fields—the direction in which the light waves oscillate—researchers can actively change the direction of the resulting electrical current.

“When you think about electrons moving through a material, they’re moving because you’ve applied an electrical field and they actually bounce around and drift across the materials,” said Steven Cundiff, a U-M physicist and senior author of the report. “Here, using light, you can actually sort of squirt the electrons in a specific direction without applying an electric field.”

While earlier studies established that light alone could cause electrons to move, the new experiment achieves greater precision. “The light no longer merely switches the current on; it also aims it,” Cundiff said.

The Quantum Mechanics Behind the Electron Lighthouse Effect

Researchers compare the operation of the device to a lighthouse sweeping a beam across the horizon, with the moving beam consisting entirely of focused electrons. This directional movement relies on quantum interference, which occurs when two colors of light send the semiconductor through different absorption pathways that ultimately lead to the same final state.

Light delivers energy to the material in discrete packets known as photons, which then mobilize the semiconductor’s electric charge carriers. In the U-M setup, the material absorbs incoming light through two pathways simultaneously. Cundiff likened the process to overlapping ripples: for electrons moving in one direction, the ripples align and reinforce each other, while for electrons traveling in other directions, they cancel one another out.

Fabricating the Device at the Lurie Nanofabrication Facility

Turning the theoretical model into physical hardware required precise manufacturing to prevent extraneous electric fields that could interfere with the results. Yiming Gong, who helped lead the project as a doctoral student in the U-M Department of Physics, manufactured the device at the Lurie Nanofabrication Facility (LNF).

“That was the biggest puzzle to solve for me, because there isn’t a standard way to do that,” Gong said, noting that he worked with LNF staff to experiment with different recipes and temperatures. Kai Wang, a former postdoctoral scientist who worked with Cundiff and is now a professor at Sun Yat-Sen University in China, also advised on the project.

Although the device was primarily built to investigate fundamental physics, the discovery could eventually support technologies combining optics and electronics, including advanced sensing, imaging, and telecommunications. Gong, who has since earned his doctorate from U-M, noted that the device has the potential to measure different aspects of light.

Frequently Asked Questions

How does light move electrons without an electric field?

The device uses two colors of light to create quantum interference through simultaneous absorption pathways. This selective reinforcement concentrates the electron current in a specific direction.

Can the direction of the electron current be controlled?

Yes. Researchers can change the direction of the current by rotating the polarization of the two optical fields.

What are the potential applications of this technology?

While designed primarily to study fundamental physics, the discovery could support technologies combining optics and electronics, such as advanced imaging, sensing, telecommunications, and improved signal transmission.