Engineers at the University of California San Diego have developed a way to write digital information using light rather than magnetic fields; if the technology makes its way into devices, it could enable denser, more energy-efficient memory. The findings were published in the journal Nature Communications.

Light Could Replace Magnetic Fields

In hard drives and other data storage devices, digital data is encoded in the magnetic states of small regions of material, corresponding to zeros and ones. An external magnetic field is typically used to switch these states. The new approach uses light to change the material's magnetization.

According to the researchers, optical switching could potentially be more than a thousand times faster than methods that rely on an external magnetic field. In addition, the ability to target extremely small regions of material could increase recording density, allowing more information to be stored in a smaller area. However, these advantages are still considered potential capabilities of the technology rather than features of a finished memory device.

Specially Shaped Light Overcomes Previous Limitations

Previously, optical switching had only been demonstrated in very thin magnetic structures consisting of no more than three layers. In addition, light with a specific polarization was required to achieve the effect. As the material's thickness increased, switching was suppressed, limiting the method's potential applications.

A team led by Professor Abdoulaye Ndao of the Jacobs School of Engineering at the University of California San Diego solved this problem by changing the characteristics of the light beam rather than the material itself. Using a specialized optical system, the researchers shaped and focused ultrafast laser pulses onto an extremely small area of the surface.

In their experiments, they successfully switched the magnetic state of a structure consisting of nine alternating layers of platinum and cobalt. They also found that a specific light polarization was no longer required.

“Instead of developing a new material that would enable optical switching, we modified the light itself and demonstrated properties that were previously considered impossible,” Ndao said.

How a Laser Writes Magnetic Information

The method involves directing several ultrashort laser pulses at the same region of material. The initial pulses heat a small area, creating a region with a changed magnetization direction. Subsequent pulses gradually expand it until the new magnetic state becomes stable.

Light thus makes it possible to control magnetic states without an external magnetic field. The size of the area targeted by the beam is crucial to the potential recording density.

“The smaller the light beam, the smaller and denser the optical memory can be,” Ndao explained.

The study brought together specialists in optics and magnetic materials. The paper's first author, graduate student Muhammad Waleed Khalid, noted that the unusual results had to be checked repeatedly to confirm that the effect was reproducible.

What Is Holding Back the Technology's Adoption

Several technical challenges must be addressed before data storage devices using this principle can become a reality. The main challenge is integrating a specialized ultrafast laser into electronic systems. The equipment currently used is difficult to incorporate directly into computer chips. The scientists are therefore also exploring magnetic materials in which a similar effect could be achieved using more compact lasers that are easier to integrate.

Another area of research is further reducing the light beam's size to a few hundred nanometers. To achieve this, the researchers are considering optical structures capable of concentrating light into an even smaller space. If these challenges can be overcome, the development could provide a foundation for denser digital data recording and faster magnetic memory operations. For now, however, the researchers have demonstrated the physical principle only under laboratory conditions. Its practical effectiveness, power consumption within a finished device, and suitability for mass production still need to be verified.