Physics Briefs

Laser lights and computers can see past some barriers

While this is certainly not the stuff of sci-fi goggles or x-ray vision, the ability to see past certain barriers is starting to come into focus. Researchers at the University of Twente in the Netherlands developed a technique that allows them to “see” through very thin layers of material that otherwise is not “see-through” in the everyday sense.

Publishing their results in the journal Nature, the group developed this technique using a disc of ground glass that allows some light to pass through, much like a thin sheet of paper, but does not allow enough light through for us to see past them. They shone a beam of laser light upon the disc, which scatters the projected light. The scattered light reflects from objects behind the disk, which the researchers were able to capture and run through a computer program to decode into an image of the object. The light that makes it back is too scrambled and low in its intensity for the naked eye to interpret.

With further development, the researchers hope to apply this discovery towards radiation-free medical imaging. Skin is another material that has a similar light scattering property fit for this laser light-based imaging.

Ions show potential to improve atomic clocks

When it comes to time accuracy, atomic clocks have been the highest standard for accuracy with nuclear clocks showing theoretical potential to do even better. In the meantime, researchers from the University of Nevada and the University of New South Wales have proposed using atomic clocks based on ions, atoms stripped of their electrons, to further enhance their accuracy.

By removing the electrons from the atoms, which they suggest should be bismuth-209, the clock would suffer from the reduction in accuracy that stray magnetic fields in current atomic clocks. Currently these clocks are accurate to one part in 10 to the 17th power and base time off of the transitions of electrons within an atom. Their goal was to increase the accuracy by two orders of magnitude.

While the researchers acknowledged the difficulty in building this clock, it would be much more feasible in the present than building nuclear clocks and advocate for more efforts into improving atomic clocks. Their results are published in the journal Physical Review Letters.

New technique makes beam of electrons act like vortexes

Electron microscopy uses beams of electrons quite extensively to image objects too small for us to view with light. Using a twist in quantum mechanics, researchers at the Vienna University of Technology have generated a vortex of electrons that move in a similar fashion to debris that is swept up in a tornado. They published their brief results in the journal Physical Review Letters.

The group of researchers provided electrons with an angular momentum, a property of subatomic particles analogous to the circular motion of larger objects in a tornado. While they had used a grid in previous experiments to split the beam into three, one with no angular momentum and two with opposite, their most recent experiment used a screen coated with a thin layer of silicon dioxide.

Because the layer is so thin, it does not absorb much of the electrons intensity, but it gives it a phase shift, another intrinsic property of waves, that causes the electrons to move in a vortex, due to the angular momentum. This beam can also transfer its angular momentum to the electrons within the object it hits, affecting its magnetic properties. The team sees the possibility of using the beam to cause other atoms and molecules to rotate as well.

Light sensor can detect faint amount of photons

Scientists at the Fraunhofer Institute for Microelectronic Circuits and Systems IMS in Duisburg and their collaborators have developed a sensor sensitive enough to detect small amounts of photons. The underlying technology is based off of an “avalanche breakdown” effect that intensifies the signal of each photon.

The sensor also processes the images directly as a camera, making image processing very rapid. Similar camera-on-a-chip technology has been used in traffic safety initiatives in Europe.