Bright, twisted light can be produced with technology similar to an Edison light bulb, researchers at the University of Michigan have shown. The finding adds nuance to fundamental physics while offering a new avenue for robotic vision systems and other applications for light that traces out a helix in space. “It’s hard to generate enough brightness when producing twisted light with traditional ways like electron or photon luminescence,” said Jun Lu, an adjunct research investigator in chemical engineering and first author of the study. “We gradually noticed that we actually have a very old way to generate these photons—not relying on photon and electron excitations, but like the bulb Edison developed.” Typically, the shape of an object emitting radiation does not get much consideration — for most purposes, the object can be imagined as a sphere. But while shape does not affect the spectrum of wavelengths of the different photons, it can affect a different property: their polarization. Researcher Jun Lu (pictured) is part of a team of researchers from the University of Michigan that demonstrated for the first time that a twisted filament could produce twirling light waves. Courtesy of the University of Michigan/Brenda Ahearn. Usually, photons from a blackbody source are randomly polarized — their waves may oscillate along any axis. The study showed that if the emitter was twisted at the micro or nanoscale, with the length of each twist similar to the wavelength of the emitted light, the blackbody radiation would be twisted too. The strength of the twisting in the light, or its elliptical polarization, depended on two main factors: how close the wavelength of the photon was to the length of each twist and the electronic properties of the material — nanocarbon or metal, in this case. Twisted light is also called “chiral” because the clockwise and counterclockwise rotations are mirror images of one another. The study was undertaken to demonstrate the premise of a more applied project that the Michigan team would like to pursue: using chiral blackbody radiation to identify objects. They envision robots and self-driving cars that can see like mantis shrimp, differentiating among light waves with different directions of twirl and degrees of twistedness. The bulb’s Edison-style filament is twisted at the microscale. When the length of each twist matches the wavelength of the light emitted by the filament, the lightwaves twirl as they move through space. Courtesy of the University of Michigan/Brenda Ahearn. “The advancements in physics of blackbody radiation by chiral nanostructures is central to this study. Such emitters are everywhere around us,” said Nicholas Kotov, the Irving Langmuir Distinguished Professor of Chemical Sciences and Engineering, director of NSF Center of Complex Particles and Particle Systems (COMPASS), and corresponding author of the study. “These findings, for example, could be important for an autonomous vehicle to tell the difference between a deer and a human, which emit light with similar wavelengths, but different helicity because deer fur has a different curl from our fabric.” While brightness is the main advantage of this method for producing twisted light—up to 100 times brighter than other approaches—the light includes a broad spectrum of both wavelengths and twists. The team has ideas about how to address this, including exploring the possibility of building a laser that relies on twisted light-emitting structures. Kotov also wants to explore further into the IR spectrum. The peak wavelength of blackbody radiation at room temperature is roughly 10,000 nm. “This is an area of the spectrum with a lot of noise, but it may be possible to enhance contrast through their elliptical polarization,” Kotov said. The research was published in Science (www.doi.org/10.1126/science.adq4068).