Harvard Scientists Manipulate Near-Field Light

Have you heard of near field-light? It is the light that stays behind when regular light hits a surface. This type of light is not transmitted or scattered away so it stays right where it was.

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It's invisible to the human eye of, course, but that does not mean it does not have useful properties. Today, it is used for ultra-high-resolution microscopy, known as the near-field scanning optical microscopes (NSOM) but a bunch of Harvard scientists believe it might be useful in particle manipulation, sensing, and optical communications.

The only thing required is to figure out how to manipulate it. Now, Harvard researchers have devised a new system to mold near-field light.

“Over the years, our group has developed new powerful techniques to structure propagating light using subwavelength-patterned metasurfaces,” said Federico Capasso, the Robert Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, and senior author of the paper.

“With this work, we show how to structure the near field at a distance, opening exciting opportunities in science and technology.”

But wait, isn't near field light invisible to the human eye? How can you manipulate what you cannot see? The researchers achieved this by developing a device in which light confined to a waveguide jumps back and forth between two reflectors.

After each jump, it changes mode. This indicates that it now propagates with a different spatial pattern. When all these different patterns are superimposed, a shape is created. The researchers can then successfully design that shape by tailoring the amplitude of the modes of the bouncing light.  

The researchers compare it to music. One note alone does not make a track but all notes together can create different genres of music. To demonstrate this theory, the researchers designed near-field light into the shape of an elephant proving that the light can indeed be manipulated.