Engineers at the University of California San Diego (UC San Diego) have developed a new way to control magnetic information using specially shaped light.
The method uses an ultrafast laser beam focused into a very small area to switch a material’s magnetic state. The researchers say the approach addresses limits that have restricted optical switching in magnetic memory.
Magnetic storage devices encode digital information through tiny magnetic regions that represent binary values such as 1 and 0.
Conventional systems change these magnetic states using external magnetic fields, which require energy and limit how quickly information can be written. Optical switching takes a different route by using short laser pulses to alter magnetization.
Light can deliver energy in extremely short periods and focus it into small regions. This gives researchers a way to target magnetic areas without applying a conventional external magnetic field. The UC San Diego team estimates that optical switching can operate more than 1,000 times faster than methods based on external magnetic fields.
Researchers at the UC San Diego Jacobs School of Engineering conducted the research. Their findings were published in Nature Communications, where the team described how controlling the shape and size of light changed the way the magnetic material responded.
The researchers used an ultrafast laser to create a highly engineered beam.
Unlike conventional laser beams, the beam was shaped and reduced to a scale far smaller than in earlier optical-switching experiments. The work focused on how this tightly controlled light interacted with magnetic material at very small scales.
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Thicker Materials Expand Options
Earlier studies had demonstrated optical switching in magnetic structures made from very thin stacks. Those experiments generally involved no more than three magnetic layers and depended on a specific light polarization. Increasing the material thickness beyond three layers had been found to suppress the switching effect.
That limitation matters because a magnetic material’s thickness and structure affect its ability to retain stored information. A restriction to very thin magnetic stacks can therefore limit the design of optical memory systems. The UC San Diego team set out to determine whether changing the light itself could remove these constraints.
The researchers demonstrated optical switching in a material containing nine alternating layers of platinum and cobalt. They also found that switching no longer depended on the incoming light’s polarization.
Abdoulaye Ndao, a professor in UC San Diego’s Department of Electrical and Computer Engineering, led the study. He said the team changed the light’s behavior rather than developing a new material designed specifically for optical switching.
The approach also has implications for data density. A smaller optical beam can address a smaller magnetic region, allowing more magnetic bits in a given area. Ndao said reducing the beam size is therefore linked to the potential to create denser optical memory.
How The Laser Switches Magnetism
The process begins when the specially shaped laser beam is concentrated onto a very small region of the magnetic material. The first ultrafast pulses raise the temperature in that localized area enough to create a reversed magnetic region. Later pulses then expand that switched region until it reaches a stable state.
This process differs from simply applying a magnetic field across the material. The researchers use the light’s spatial shape and timing to control where the magnetic change begins and how it develops. This gives them another way to manipulate magnetization without relying on the polarization conditions used in earlier experiments.
Muhammad Waleed Khalid, the study’s first author and an electrical and computer engineering Ph.D. student in Ndao’s research group, said the specially engineered beam allowed the team to investigate physical effects that are difficult to observe with conventional laser beams.
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The experiments also required extensive verification. Khalid said the researchers initially found the results difficult to explain and spent considerable time repeating the experiments to confirm that the observations were consistent.
The work combined two areas that are often studied separately. Ndao’s group specializes in optics, while Eric Fullerton’s research focuses on thin-film magnetic materials and magnetic memory.
Fullerton is a professor of electrical and computer engineering, as well as chemical and nano engineering, at UC San Diego, and holds an endowed chair at the university’s Center for Memory and Recording Research.
Smaller Lasers Remain A Challenge
The researchers say the current system is still a laboratory technology. It relies on a specialized ultrafast laser that is not yet easy to integrate into computer chips or conventional electronic hardware.
One possible route is to find magnetic materials that show similar behavior when exposed to lasers that are smaller, simpler, or easier to integrate into electronic systems. The team is also working on reducing the size of the engineered beam itself. Its target is a beam measuring only a few hundred nanometers.
The researchers are examining optical structures that can confine light into even smaller spaces. Such structures may help them study how light can control magnetism at increasingly small scales.
Several research programs and institutions supported the work.
Funding included the 2023 Beckman Young Investigator Award, the Arnold and Mabel Beckman Foundation, the 2024 Alfred P. Sloan Research Fellowship, the Moore Foundation’s PAIR UP Imaging Science Program and the Air Force Office of Scientific Research MURI program under Award No. FA9550-22-1-0312.
The National Science Foundation also supported the research through the UC San Diego Materials Research Science and Engineering Center under grant DMR-2614051. Part of the work was conducted at the San Diego Nanotechnology Infrastructure at UC San Diego, which is part of the National Nanotechnology Coordinated Infrastructure and receives NSF support under grant ECCS-2025752.
The next stage will focus on making the optical system smaller and finding practical ways to connect engineered light with magnetic memory technologies. If the researchers can reproduce the switching effect with more compact optical components and suitable magnetic materials, the work may provide another route toward high-density, high-speed data storage.
