'Scientists Just Created Spacetime Crystals Made of Knotted Light'

By exploiting two-color beams, researchers 'can generate ordered chains and lattices,' reports ScienceDaily, 'with tunable topology — potentially revolutionizing data storage, communications, and photonic processing.'

An internationally joint research group between Singapore and Japan has unveiled a blueprint for arranging exotic, knot-like patterns of light into repeatable crystals that extend across both space and time. The work lays out how to build and control 'hopfion' lattices using structured beams.. three-dimensional topological textures whose internal 'spin' patterns weave into closed, interlinked loops.

They have been observed or theorized in magnets and light fields, but previously they were mainly produced as isolated objects. The authors show how to assemble them into ordered arrays that repeat periodically, much like atoms in a crystal, only here the pattern repeats in time as well as in space. The key is a two-color, or bichromatic, light field whose electric vector traces a changing polarization state over time. By carefully superimposing beams with different spatial modes and opposite circular polarizations, the team defines a 'pseudospin' that evolves in a controlled rhythm. When the two colors are set to a simple ratio, the field beats with a fixed period, creating a chain of hopfions that recur every cycle. Starting from this one-dimensional chain, the researchers then describe how to sculpt higher-order versions whose topological strength can be dialed up or down...

Topological textures like skyrmions have already reshaped ideas for dense, low-error data storage and signal routing. Extending that toolkit to hopfion crystals in light could unlock high-dimensional encoding schemes, resilient communications, atom trapping strategies, and new light-matter interactions. 'The birth of space-time hopfion crystals,' the authors write, opens a path to condensed, robust topological information processing across optical, terahertz, and microwave domains.

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