Twisted Edison: A nanoscale curled filament produces light waves that rotate as they travel.

Bright, twisted light can be produced using technology similar to the Edison light bulb, researchers at the University of Michigan have shown. The discovery adds nuance to fundamental physics while providing new avenues for robotic vision systems and other applications of light that track spirals in space.

“When producing twisted light using traditional methods such as electroluminescence or photon luminescence, it is difficult to generate sufficient brightness,” says John, an adjunct research fellow in chemical engineering at UM and in this week’s issue of Science said Jun Lu, lead author of the study featured on the cover of .

“We gradually realized that there was actually a very old way of producing these photons, which did not rely on the excitation of photons and electrons, but something like the light bulb that Edison developed. .”

Any object that has some heat, including yourself, constantly emits photons (particles of light) in the spectrum associated with its temperature. If an object is at the same temperature as its surroundings, it will also absorb the same amount of photons. Since black color absorbs all photon frequencies, this is idealized as “blackbody radiation.”

Although the filament of a tungsten bulb is much warmer than its surroundings, the law that defines blackbody radiation (Planck’s law) provides a good approximation of the spectrum of photons that a tungsten bulb transmits. The photons we see as a whole look like white light, but when we pass light through a prism, we see a rainbow of different photons inside.

This radiation is also why it appears bright in thermal images, but even room-temperature objects can appear dark because they are constantly emitting and receiving blackbody photons.

Usually, the shape of the object that emits radiation is not much considered. For most purposes (as is often the case in physics), objects can be imagined as spheres. However, while the shape does not affect the spectrum of different photon wavelengths, it can affect another property: polarization.

Photons from a blackbody source are typically randomly polarized, and their waves can oscillate along any axis. New research reveals that blackbody radiation is also twisted when the emitter is twisted on the microscale or nanoscale, with the length of each twist similar to the wavelength of the emitted light. The strength of the twist of light, or elliptical polarization, depends primarily on two factors. One is how close the wavelength of the photon is to the length of each twist, and the other is the electronic properties of the material (in this case, nanocarbon or metal).

Twisted light is also called “chiral” because the clockwise and counterclockwise rotations are mirror images of each other. The study was done to demonstrate the premise of a more applied project that the Michigan team hopes to pursue: using chiral blackbody radiation to identify objects. They envision robots and self-driving cars that can see like a mantis shrimp, distinguishing light waves in different directions of rotation and degrees of twist.

“Advances in the physics of blackbody radiation through chiral nanostructures are central to this research. Such emitters are all around us,” said Irving Langmuir Distinguished Professor of Chemical Sciences and Engineering. Yes, said Nicholas Kotov, director of the NSF Center for Composite Particles and Particle Systems. (COMPASS) and corresponding author of the study.

“For example, these findings could be important in helping autonomous vehicles tell the difference between a deer and a human. Deer fur curls differently than our fabric, so even though the wavelengths are similar, Helicity emits a different light.”

The main advantage of this method of producing twisted light is its brightness, which is up to 100 times brighter than other approaches, while the light contains a wide spectrum of both wavelengths and twists. The team has ideas on how to address this, including exploring the possibility of building lasers that rely on twisted light-emitting structures.

Kotov also wants to further explore the infrared spectrum. The peak wavelength of blackbody radiation at room temperature is approximately 10,000 nanometers or 0.01 millimeter.

“This is a noisy spectral region, but elliptical polarization could potentially enhance the contrast,” Kotov said.

Kotov is also the Joseph B. and Florence V. Cheika Professor of Engineering, professor of polymer science and engineering, and a member of UM’s Biointerfaces Laboratory. Lu is an incoming assistant professor of chemistry and physics at the National University of Singapore.

The device was built in the COMPASS Lab at UM’s North Campus Research Facility and researched at the Michigan Center for Materials Characterization.