Researchers Structure Light with Two Independent Orbital Angular Momenta

Researchers at the University of Southern California (USC) have combined twisted light and optical frequency combs to produce a new, dynamic light structure. The discovery has potential to advance understanding of light generation and propagation, and could benefit sensing, imaging, smart manufacturing, and metrology.

The discovery stems from the intersection of two distinct research paths. The Optical Communications Lab at USC had been separately researching twisted light beams and frequency combs. The merger occurred when researcher Zhe Zhao considered the potential effects of combining different optical frequencies and twisted light.

Orbital angular momentum (OAM), or twisted light, can be activated in different forms, including a Gaussian-like beam dot that revolves around a central axis and a Laguerre-Gaussian beam with a helical phasefront rotating around its own beam center. Researchers generated dynamic spatiotemporal beams that combined these two forms of OAM by coherently adding multiple frequency comb lines. The structure of the generated spatiotemporal light beam could be tuned by changing the spatial Laguerre-Gaussian mode distribution.

When the researchers simulated these generated beams they achieved a mode purity up to 99% and control of the helical phasefront from 2π to 6π and a revolving speed from 0.2 to 0.6 THz. The team believes its approach could be used to generate spatiotemporal beams with even more sophisticated dynamic properties.

“Simply put, through this technique light can be tailored in more detailed and exquisite ways than ever before,” Zhao said.

For now, the research group is focusing on what other dynamic light structures they can build using this new approach to generating dynamic spatiotemporal beams that combine two independent, controllable OAMs.

The research was published in Nature Communications (www.doi.org/10.1038/s41467-020-17805-1).