Harvard researchers have developed a metasurface material that can generate and maintain completely new and more complex states of light.
Discoveries in the field of the behavior of light continue: back in 2015, scientists obtained the first photograph of the state of light, in which it behaves simultaneously as a particle and as a wave. And quite recently, just 25 years ago, the orbital angular momentum was discovered in photons.
It is angular momentum based on the shape of its wavefront, not orientation. The new metasurface material uses it together with a second type of angular momentum called spin moment (also better known as circular polarization).
Analogies can be drawn between orbital angular momentum and circular polarization, comparing them to the motion of planets: circular polarization is the direction in which a planet rotates on its axis, and orbital moment describes how a planet revolves around the sun.
It has previously been found that the same light beam can exhibit both types of angular momentum, and that their combination and the use of polarization to control optical amplitude modulation (OAM) can result in beams with new complex shapes.
Some metasurfaces are more efficient and more compact versions of existing optical devices, but such arbitrary conversions between spins and orbits cannot be performed by any other optical device.
The orbital angular momentum of photons already has several contemplated applications such as high speed data transmission and message coding. The researchers even figured out how to transmit the OAM of individual photons using their entanglement.
Other suggested practical applications of the new material include manipulation of microscopic objects and applications in imaging systems.
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