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.
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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.
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| (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."
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.
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.
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.