Engineers at the University of California San Diego have developed an optical switching technique using a specialized ultrafast laser, research published in the journal Nature Communications. This breakthrough allows light to alter magnetic states at speeds more than 1,000 times greater than conventional external magnetic fields, overcoming historical thickness limits in magnetic memory structures.
University of California San Diego Engineers Redesign Laser Beams
Modern hard drives rely on tiny magnetic regions to encode digital information as 1s and 0s. Writing new data typically requires applying an external magnetic field to change the orientation of these regions. This conventional process consumes considerable energy and limits recording speeds. The UC San Diego research team demonstrated that optical switching can deliver energy in extremely short bursts focused onto remarkably small areas.
To achieve this, the engineers used a specialized ultrafast laser and carefully modified the shape and size of its beam. Muhammad Waleed Khalid, an electrical and computer engineering Ph.D. student in the research group, explained the methodology:
“Working with a specialized laser allowed us to optically engineer the beam to have a certain shape and size. That gave us the room to explore more fundamental physics, which cannot be done with conventional beam lasers.”
Compared to past trials, the generated beam was vastly smaller, with the team noting a decrease spanning tens of orders of magnitude. This precise control allows laser energy to be directed onto smaller magnetic regions, enabling future memory devices to hold more data without increasing their physical size.
Overcoming Thickness Limits in Magnetic Structures
Until this research, optical switching faced two critical restrictions. Earlier experiments succeeded only with extremely thin magnetic structures containing no more than three magnetic layers. The process also required light with a particular polarization.
Abdoulaye Ndao, who serves as study senior author and professor within the Department of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering, explained the past limitation:
“Past experiments had found that increasing the material’s thickness beyond three layers suppressed optical switching. That put a constraint on the overall thickness of the magnetic material and thus, its ability to retain memory in the long term.”
By reshaping and reducing the size of the laser beam, Ndao and his colleagues bypassed both obstacles. They demonstrated optical switching in a substantially thicker magnetic structure containing nine alternating layers of platinum and cobalt. The process worked without requiring a particular polarization of light.
Muhammad Waleed Khalid described the underlying mechanism:
“We’ve optically engineered the light to change the physics that’s happening in the material at the micro- and nanoscale.”
The technique concentrates laser energy into an extremely small region using a sequence of ultrafast pulses. A localized zone of the magnetic material experiences brief heating from the initial pulses, which flips the magnetic orientation of a minor area. Additional pulses gradually enlarge that reversed region until the new magnetic state becomes stable.
Verification Challenges Across Optics and Magnetic Materials
The breakthrough emerged from a collaboration between researchers specializing in optics and those focusing on magnetic materials. Ndao’s optics research team worked alongside Eric Fullerton, an expert in thin-film magnetic materials at UC San Diego. Fullerton holds professorships in electrical and computer engineering as well as chemical and nano engineering, while also acting as the Endowed Chair Professor at the institution’s Center for Memory and Recording Research.
Abdoulaye Ndao summarized the collaborative approach:
“Instead of designing a new material to enable optical switching, we redesigned the light itself and showed new properties that were not previously thought to be possible.”
The unusual results initially proved difficult to establish within the scientific community. Because the effects differed greatly from prior assumptions, the researchers spent significant time and effort repeating and verifying their experiments to substantiate their findings to the optics community.
Hardware Integration Obstacles Remaining for Future Memory Devices
Significant technical obstacles remain before optical switching can transition into everyday electronic devices. The primary challenge involves the specialized ultrafast laser required for the experiments, as current versions are not easily incorporated into computer chips.
The research team is exploring alternative ways to achieve similar results. They are investigating magnetic materials that could respond to laser systems more suitable for electronic hardware integration. Additionally, the researchers are attempting to reduce the laser beam’s size even further, targeting a scale of just a few hundred nanometers by exploring optical structures capable of concentrating light into progressively smaller regions.
