System Bits: Dec. 23

Mini particle accelerator
Researchers at MIT who succeeded last year in creating a material that could trap light and stop it in its tracks have now developed a more fundamental understanding of the process. The new work — which they said could help explain some basic physical mechanisms — shows that this behavior is connected to a wide range of other seemingly unrelated phenomena.

Light can usually be confined only with mirrors, or with specialized materials such as photonic crystals. Both of these approaches block light beams; last year’s finding demonstrated a new method in which the waves cancel out their own radiation fields. The new work shows that this light-trapping process, which involves twisting the polarization direction of the light, is based on a kind of vortex — the same phenomenon behind everything from tornadoes to water swirling down a drain.

In addition to revealing the mechanism responsible for trapping the light, the new analysis shows that this trapped state is much more stable than had been thought, making it easier to produce and harder to disturb.

Vortices of bound states in the continuum. The left panel shows five bound states in the continuum in a photonic crystal slab as bright spots. The right panel shows the polarization vector field in the same region as the left panel, revealing five vortices at the locations of the bound states in the continuum. These vortices are characterized with topological charges +1 or -1. (Source: MIT)

The phenomenon makes it possible to produce something called a vector beam, a special kind of laser beam that could potentially create small-scale particle accelerators. Such devices could use these vector beams to accelerate particles and smash them into each other — perhaps allowing future tabletop devices to carry out the kinds of high-energy experiments that today require miles-wide circular tunnels.

Atom-thick charged-coupled device could take pictures
An atomically thin material developed by Rice University researchers has the potential to lead to the thinnest-ever imaging platform.

Synthetic two-dimensional materials based on metal chalcogenide compounds could be the basis for superthin devices, according to Rice researchers. One such material, molybdenum disulfide, is being widely studied for its light-detecting properties, but copper indium selenide (CIS) also shows extraordinary promise.

Researchers in a materials lab synthesized CIS, a single-layer matrix of copper, indium and selenium atoms, as well as a prototype — a three-pixel, charge-coupled device (CCD) — to prove the material’s ability to capture an image.

They believe optoelectronic memory material could be an important component in two-dimensional electronics that capture images.

A schematic shows the design of an optoelectronic memory device based on CIS, a two-dimensional material developed at Rice University. The device traps electrons formed when light hits the material and holds them until released for storage; it could form the basis of future flat imaging devices. (Source: Rice University)