Credit: Sean Kelly/NIST
For some 30 years, scientists have used superconducting materials to record the tiniest specks of light imaginable — individual photons, or single particles of light. However, these detectors, which consist of ultracold wires only about one-thousandth the diameter of a human hair, were limited to recording single photons at visible-light and slightly longer wavelengths, in the near infrared (IR).
By altering the composition of these nanowires, researchers at the National Institute of Standards and Technology (NIST) and their colleagues have now demonstrated that the devices can efficiently record single photons that have wavelengths up to 10 micrometers (millionths of a meter), five times longer than previously possible. These invisible wavelengths of light, which fall in the mid-IR part of the electromagnetic spectrum (see chart), are emitted when bodies radiate heat. The human body radiates the majority of its heat at 10 micrometers.
The ability to detect photons at mid-IR wavelengths opens the window on vast new opportunities for research and applications, including an enhanced search for chemical signs of life on other planets, the stealth navigation of vehicles in pitch darkness, and the search for dark matter, the invisible material believed to account for about 80 percent of the mass of the universe.
Earth scientists trying to understand the evolution and changing climate of our planet, as well as astronomers searching for signs of life beyond the solar system, have a particular interest in detecting individual mid-IR photons. That’s because many molecules that may indicate biological activity all have a special “fingerprint” — their existence and abundance can be identified by the specific wavelengths of mid-IR light that they absorb.
Astronomers hunting for hints of biological activity beyond the solar system record the extraordinarily faint light of distant stars filtering through th ..
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