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Ampliflying Light 10,000 Times

Experimental techniques could make dim objects far easier to see

2 min read
Ampliflying Light 10,000 Times
Image: University of Wisconsin-Madison

A new type of device could amplify the light emitted by a nanometer-scale object as much as 10,000 times, improving low-light photography and bringing previously hard-to-see items into view.

“It actually scatters more light. It also can absorb more light,” says Ming Zhou, a doctoral candidate in Zongfu Yu’s Nanophotonics Lab at the University of Wisconsin, Madison.

The device is based on a nanoresonator, which is similar to a laser cavity in that it bounces photons back and forth between mirrors, allowing them to amplify each other. The trouble is that the nanoresonator is so small (only a few hundred nanometers in cross-section for visible wavelengths) that even the amplified light is not bright enough to be easily seen.

imgThe nanoresonator, which is embedded in a material with an index of 0.02,  is small compared with the light from a laser beam. But when the beam moves over it, the resonator scatters the light at many times its own diameter, creating a bright circle.Illustration: University of Wisconsin-Madison

But the light can be amplified by a far greater amount if the nanoresonator is embedded in a material with an extremely low—but greater than zero—index of refraction. In vacuum, light bouncing off an object can scatter in any direction, spreading it thin. But when it moves through a material with a very low index of refraction, the options for scattering become much fewer, concentrating the light in a particular direction. Inside the material, the wavelength of light becomes much larger, leading it to resonate much more strongly. The concentrated light that emerges, back at its normal wavelength, is far brighter than what started out.  A material with a refractive index of 0.01, for instance, would amplify the light 10,000-fold.

The low-index material could be built by creating a structure that alternates between two different materials; each layer would be 10 to 20 nanometers thick if the wavelength in question is 1000 nm, and even thinner for shorter wavelengths. A structure of this type, Zhou says, is not easy to fabricate. So far, the team has tested its theory only in computer simulations, the results of which the researchers explained in a recent paper published in the journal Physical Review Letters. They are now working on a physical demonstration.

Enhancing light by the amount they describe could magnify objects, and could make photography under extreme low-light conditions easier. Another possible use for such a device would be as a solar concentrator, directing vastly more sunlight onto a given area of a solar cell. “We can absorb much more light than a current device,” says Zhou. “The performance will be better.”

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3 Ways 3D Chip Tech Is Upending Computing

AMD, Graphcore, and Intel show why the industry’s leading edge is going vertical

8 min read
Vertical
A stack of 3 images.  One of a chip, another is a group of chips and a single grey chip.
Intel; Graphcore; AMD
DarkBlue1

A crop of high-performance processors is showing that the new direction for continuing Moore’s Law is all about up. Each generation of processor needs to perform better than the last, and, at its most basic, that means integrating more logic onto the silicon. But there are two problems: One is that our ability to shrink transistors and the logic and memory blocks they make up is slowing down. The other is that chips have reached their size limits. Photolithography tools can pattern only an area of about 850 square millimeters, which is about the size of a top-of-the-line Nvidia GPU.

For a few years now, developers of systems-on-chips have begun to break up their ever-larger designs into smaller chiplets and link them together inside the same package to effectively increase the silicon area, among other advantages. In CPUs, these links have mostly been so-called 2.5D, where the chiplets are set beside each other and connected using short, dense interconnects. Momentum for this type of integration will likely only grow now that most of the major manufacturers have agreed on a 2.5D chiplet-to-chiplet communications standard.

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