Category Physics

Image of one of the graphene-based devices Xu and colleagues worked with. Credit: Lei Wang

In traditional light-harvesting methods, energy from 1 photon only excites 1 electron or none depending on the absorber’s energy gap. The remaining energy is lost as heat. But a new article describe an approach to coax photons into stimulating multiple electrons. Their method exploits some surprising quantum-level interactions to give one photon multiple potential electron partners.

Wu and Xu in UW’s Dept of Materials Science & Engineering and the Det of Physics, made this surprising discovery using graphene.
The researchers took a single atom layer of graphene and sandwiched it between 2 thin layers of boron-nitride. Electrons do not flow easily within boron-nitride so it is an insulator.

When the g...

This is an optical nanocavity made, from top to bottom, of molybdenum disulfide (MoS2), aluminum oxide and aluminum. Credit: University at Buffalo

The future of movies and manufacturing may be in 3D, but electronics and photonics are going 2D semiconducting materials. One of the latest advancements centers on molybdenum disulfide (MoS2), while commonly used in lubricants and steel alloys, is still being explored inoptoelectronics. Recently, engineers placed a single layer of MoS2 molecules on top of a photonic structure called an optical nanocavity made of aluminum oxide and aluminum. (A nanocavity is an arrangement of mirrors that allows beams of light to circulate in closed paths which build things like lasers and optical fibers used for communications.)

The MoS2 nanocavity can increase ...

Holograms projected on a white screen while changing the wavelength of light from blue to red. (Image courtesy of the Capasso Lab)

Nanotechnology improves holographic capabilities by encoding light polarization. Holograms are a ubiquitous part of our lives. They are in our wallets — protecting credit cards, cash and driver’s licenses from fraud — in grocery store scanners and biomedical devices. Even though holographic technology has been around for decades, researchers still struggle to make compact holograms more efficient, complex and secure.

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences have programmed polarization into compact holograms...

Multiple reflections like in a drop of paint

Inside a drop of paint, light is scattered so often that it seems impossible to demonstrate quantum effects. But despite the thousands of possible paths the light can take, researchers of the Uni of Twente now show that there are just 2 exits. Depending on the light pattern that enters the paint, 2 photons always come out through the same exit, or through different ones – as though they avoid each other.

Most of the experiments showing that light sometimes behaves like a wave and sometimes like a particle, are as simple as possible: a physics textbook example is Young’s two slit experiment. The number of possible light paths is limited, but even at this level, the experiments strongly challenge our intuition...