“Optical Rotatum” – Harvard Scientists Find a New Type of Light Structure
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| What Is Optical Rotatum? | New Discovery| Uniexpro.in |
What Is Optical Rotatum? Harvard’s Game-Changing Light Beam Discovery
Scientists at Harvard have found a new kind of light structure and called it the “optical rotatum.” Light can already be shaped into spiral forms called optical vortices, and these are used in many areas. But now, researchers at Harvard’s School of Engineering and Applied Sciences (SEAS) have made a new type of vortex light beam. This light does not just twist as it moves—it changes how fast it twists in different areas, making new and special patterns. The light behaves like the natural spiral shapes we see in things like shells and plants.
The team used an idea from physics to name their new light beam. They called it a “rotatum” to show how the twisting force, or torque, changes slowly over time. In Newton’s science, “rotatum” means how fast the torque on an object changes with time.
This optical rotatum was made in the lab of Professor Federico Capasso, a leading physics expert at SEAS. “This is a new way light behaves,” Capasso said. “It’s a vortex beam that travels and changes in special ways. It may help us move and control tiny particles.” Their research was published in Science Advances.
Light That Follows Nature’s Spirals
Interestingly, the new light beam grows in a pattern found often in nature. The pattern is based on the Fibonacci sequence, which you may know from books like The Da Vinci Code. The light beam moves in a logarithmic spiral, like what we see in the shell of a nautilus, the seeds of a sunflower, or tree branches.
“This discovery was surprising,” said Ahmed Dorrah, the main author of the study and now a professor in the Netherlands. “We hope math experts will study this more and learn something new about these universal patterns.”
More Control with Metasurfaces
This work builds on older research where the team used metasurfaces—very thin lenses with nano-sized patterns—to control light beams. These surfaces can bend light and change its shape. The scientists used them to change the light’s twist and direction. Now, they can also control the torque of the light as it moves.
“We’ve shown we can control light even more now, and do it in a smooth way,” said Alfonso Palmieri, a student in Capasso’s lab and co-author of the study.
New Uses for the Optical Rotatum
This special light beam could be used to control tiny particles, like colloids in liquids. The new twisting force could give us a new way to move small things using light. It might also lead to optical tweezers—tiny tools to pick up and move small items using light.
Other researchers have made light with changing torque before, but they used powerful lasers and large setups. The Harvard team made theirs using just a simple LCD screen and a low-power light beam. Their device is small and easy to use, so it’s much closer to being used in real-world technology.
Reference: “Rotatum of light” by Ahmed H. Dorrah, Alfonso Palmieri, Lisa Li, and Federico Capasso, published April 11, 2025, in Science Advances.
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