Researchers at the University of Michigan developed a new type of incandescent light bulb capable of emitting bright, twisted light—known as chiral light—using technology reminiscent of Thomas Edison's light bulb, according to Phys.org. This innovation revisits the classic concept of blackbody radiation, the type of light emitted by any warm object, including Edison's tungsten bulb.
Twisted light is also called chiral because the clockwise and counterclockwise rotations are mirror images of one another. The phenomenon of chiral light holds promise for advanced imaging and sensing technologies. The main advantage of the University of Michigan's method for producing twisted light is increased brightness, with the light being up to 100 times brighter than traditional techniques, Phys.org reported.
Dr. Jun Lu, the study’s lead author, highlighted the limitations of existing methods. "It's hard to generate enough brightness when producing twisted light with traditional ways like electron or photon luminescence," he said. "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," he added.
A traditional Edison lamp works by heating a tungsten filament, and this process is described by the law of radiation of an absolutely black body, discovered by Max Planck. While a tungsten light bulb's filament is much warmer than its surroundings, Planck's law offers a good approximation of the spectrum of photons it emits. The new study from the University of Michigan revealed that if the emitter is 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 as well.
Nicholas Kotov, the Irving Langmuir Distinguished Professor of Chemical Sciences and Engineering at the University of Michigan and the study’s corresponding author, emphasized the ubiquity of such emitters. "Such emitters are everywhere around us," he noted, according to Phys.org. He explained that while the shape of the object emitting blackbody radiation doesn't typically receive much consideration—often imagined as a sphere—it can affect the polarization of the emitted photons.
The visible photons emitted by a tungsten light bulb's filament combine to look like white light, but when the light is passed through a prism, a rainbow of different photons can be seen. Usually, photons from a blackbody source are randomly polarized, meaning their waves may oscillate along any axis. However, the University of Michigan team discovered that the shape of the emitter can impart a specific twist to the light.
The strength of the twisting in the light, or its elliptical polarization, depends on two main factors: how close the wavelength of the photon is to the length of each twist, and the electronic properties of the material—nanocarbon or metal, in this case. This 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.
The researchers envision robots and self-driving cars that can see like mantis shrimp, differentiating among light waves with different directions of twist and degrees of twistedness. This capability could enhance object detection and surface texture recognition by providing more contrast. Kotov noted that these findings could help autonomous vehicles distinguish between a deer and a human, as they emit light with similar wavelengths but different helicity due to the curl of deer fur compared to human fabric.
The study was undertaken to demonstrate the premise of a more applied project that the University of Michigan team would like to pursue: using chiral blackbody radiation to identify objects. Kotov expressed interest in exploring further into the infrared spectrum. "This is an area of the spectrum with a lot of noise, but it may be possible to enhance contrast through their elliptical polarization," he said.
Science Daily, New Atlas, and Sci.News reported on the new bulb, among other websites.
This article was written in collaboration with generative AI company Alchemiq