Light Passing thru Solids
North American researchers say they have generated a new platform in which light beams communicate with one another through solid matter, establishing the foundation to explore a new form of computing.

The technology, described in a paper in the journal PNAS, combines a form of hydrogel developed at Harvard University in the US with light manipulation and measurement techniques performed in a lab at Canada's McMaster University.

The resulting translucent material, which resembles raspberry jelly, incorporates light-responsive molecules whose structure changes in the presence of light, giving it special properties both to contain light beams and to transmit information between them.

Typically, beams of light broaden as they travel, but the gel is able to contain filaments of laser light along their pathway through the material, as though the light were being channelled through a pipe.

When multiple laser beams, each about half the diameter of a human hair, are shone through the same material, the researchers have established that they affect one another's intensity, even without their optical fields overlapping at all.

The interaction between those filaments of light can be stopped, started, managed and read, producing a predictable, high-speed output.

"Though they are separated, the beams still see each other and change as a result," says McMaster's Kalaichelvi Saravanamuttu, who specialises in the chemistry of materials that respond to light.

"We can imagine, in the long term, designing computing operations using this intelligent responsiveness."

Harvard's Amos Meeks says the technology helps to advance the idea of all-optical computing - computations done solely with beams of light.

"Most computation right now uses hard materials such as metal wires, semiconductors and photodiodes, to couple electronics to light," he says.

"The idea behind all optical computing is to remove those rigid components and control light with light. Imagine, for example, an entirely soft, circuitry-free robot driven by light from the sun."