98% of all the photons of light emitted since the Big Bang have wavelengths in the terahertz (THz) region of the electromagnetic spectrum, which lies between the far infrared and microwaves. These photons are strongly absorbed by Earth's atmosphere, so future space-based THz telescopes will be crucial for astrophysics research. However, current state-of-the-art detectors will need to be much more sensitive to efficiently capture THz light.

A team of researchers from Rutgers University, the CalTech/NASA Jet Propulsion Lab (JPL), and the State University of New York, Buffalo, have now taken an important step forward in this field. Their device consists of a nanosized island of titanium connected to niobium nanowires. The titanium nanoisland is superconducting (that is, it loses all resistance to electrical current) when cooled to 0.2° above absolute zero. The device, which is 500 nm long and 100 nm wide, is more sensitive to sub-millimetre and infrared wavelengths than previous such detectors because it is better thermally isolated from its surroundings and has an extremely low heat capacity.

By detecting the tiny amounts of heat generated in the titanium section when terahertz light hits the device, the researchers are able to measure the energy absorbed by the detector. The bolometer is sensitive enough to detect single photons of far infrared light.

"Space-borne telescope carrying such detectors will explore the development of large-scale structure in the universe," Michael Gershenson, one of the leaders of the project, told nanotechweb.org. "This includes early star and galaxy formation."

Such telescopes should be ready in the coming decades.

The scientists at JPL are continuing to characterise the optical properties of the device while the Rutgers team is responsible for fabrication and electrical characterisation. The final goal is to develop a large array containing around 1000 such detectors for use in background-limited, moderate-resolution THz spectrometers for next-generation space-borne telescopes, added Gershenson.

The work was presented in Nature Nanotechnology.