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Harvard Scientists Have Just Unlocked Unexpected New States of Light

Possibly we’d never run out of the diverse ways to learn more about this ubiquitous and tremendously enigmatic module; light. Discoveries are still being made. It was only in 2015 that scientists photographed light behaving both as a particle and a wave. In 1992, light was discovered to have orbital angular momentum. 

(Credit: Capasso Lab/Harvard SEAS)

This angular momentum hinge on the shape of its wave-front instead of its orientation.

Researchers at Harvard, with a recent development, can now engender new and more complex states of light. The method involves polarization to generate different structures, like swirling vortices, spirals, and corkscrews, not only helping further explore light's properties but also has potential practical implications, such as high-powered imaging.

This system, with a meta-surface, uses this along with spin angular momentum, also known as circular polarization. The meta-surface could help shape optical tweezers to manipulate objects at molecular level. Changing the polarization could change the direction of the applied force.
(Credit: Capasso Lab/Harvard SEAS)

Harvard's Leah Burrows states, "Think about orbital angular momentum and circular polarization like the motion of a planet. Circular polarization is the direction in which a planet rotates on its axis while orbital momentum describes how the planet orbits the sun." 

A single beam of light was considered to be instituting both types of angular momentum; getting them connected, and using polarization to control the OAM. That could, theoretically, produce beams with new and complex shapes within a certain limit. Although, only certain polarizations could connect to certain OAMs. Now this latest Harvard’s research bumps in; allowing any polarization to be converted to any OAM, creating spirals and corkscrews and vortices of any size. Researchers have even figured out how to transmit the OAM of individual photons using entanglement.

"This is a completely new optical component. Some meta-surfaces are iterations or more efficient, more compact versions of existing optical devices but, this arbitrary spin-to-orbital conversion cannot be done with any other optical device," said co-first researcher Antonio Ambrosio and Principal Scientist at Harvard Center for Nanoscale Systems.

"There is nothing in nature as well that can do this and produce these states of light."

Harvard’s device is found to be practical in the manipulation of microscopic objects and high-powered imaging systems, researchers said.

The co-first researcher, Noah Rubin, explained that there is interest in these beams in quantum optics and quantum information. “On the more applied side, these beams could find application in free-space optical communication, especially in scattering environments where this is usually difficult. 

Moreover, it has been recently shown that similar elements can be incorporated into lasers, directly producing these novel states of light. This may lead to unforeseen applications."

With direct applications in high-speed data transfer and encoded communications, Harvard has legally protected all IP, related to the project, and has plans to further commercialize its services. The research has been published in the journal Science.

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