Electrons in a magnetic field can display striking behaviors, from the formation of discrete energy levels to the quantum Hall effect. These discoveries have shaped our understanding of quantum materials and topological phases of matter. Light, however, is made of neutral particles and does not naturally respond to magnetic fields in the same way. This has limited the ability of researchers to reproduce such effects in optical systems, particularly at the high frequencies used in modern communications.
To address this challenge, researchers from Shanghai Jiao Tong University and Sun Yat-Sen University have developed a method for generating pseudomagnetic fields—synthetic fields that mimic the influence of real magnetic fields—inside nanostructured materials known as photonic crystals. Their research is reported in Advanced Photonics . Unlike previous demonstrations, which focused on specific effects such as photonic Landau levels, the new approach allows arbitrary control of how light flows within the material.
The team achieved this by systematically altering the symmetry of tiny repeating units in silicon photonic crystals. Adjusting the degree of local asymmetry at each point allowed them to "design" pseudomagnetic fields with tailored spatial patterns, without breaking fundamental time-reversal symmetry. Both theoretical analysis and experiments confirmed that these engineered fields can guide and manipulate light in versatile ways.
To demonstrate practical applications, the researchers built two devices commonly used in integrated optics. One was a compact S-shaped waveguide bend that transmitted light with less than 1.83 decibels of signal loss. The other was a power splitter that divided light into two equal paths with low excess loss and minimal imbalance. In a final test, the devices successfully transmitted a high-speed data stream at 140 gigabits per second using a standard telecommunications modulation format, showing that the technique is compatible with existing optical communication systems.
Demonstration of a straight waveguide, a S-bend and a 50:50 power splitter based on PMFs. (a), (b) Schematic of the PhC structures of the S-bend and the power splitter. The PMF distributions in supercells along the propagation direction are shown on the bottom of the figures. (c), (d) Simulated propagation profiles for the straight waveguide, the S-bend and the power splitter. (e), (f) Simulated and measured transmission spectra of the three devices. (g) Eye diagrams of the PAM-4 signals for different channels of the S-bend and the power splitter. Credit: P. Hu et al. doi 10.1117/1.AP.7.6.066001
Beyond immediate applications, the work opens new avenues for studying quantum-inspired phenomena with light. The ability to impose artificial gauge fields in photonic systems could enable devices for optical computing, quantum information, and advanced communication technologies. It also provides physicists with a platform to explore how neutral particles behave under conditions that mimic the presence of magnetic fields, bridging concepts from condensed-matter physics and photonics.
For details, see the original Gold Open Access article by P. Hu et al., " Arbitrary control of the flow of light using pseudomagnetic fields in photonic crystals at telecommunication wavelengths ," Adv. Photon. 6(6) 066001 (2025), doi: 10.1117/1.AP.7.6.066001 .
