New terahertz detector could observe galaxies in unprecedented detail

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Ning Wang, the study’s lead author, and Professor Mona Jarrahi working on the terahertz detector setup. (Image: UCLA Engineering)

Researchers have developed an ultra-sensitive light-detecting system capable of operating at room temperature that could enable astronomers to view galaxies, stars and planetary systems in unprecedented detail.

Reported in Nature Astronomy, the sensor system detects radiation in the terahertz band of the electromagnetic spectrum, which includes parts of the far-infrared and microwave frequencies. It can detect terahertz waves across a broad spectral range – an improvement of at least 10 times more than current technologies – which could allow it to undertake observations that currently require several different instruments to perform.

‘Looking in terahertz frequencies allows us to see details that we can’t see in other parts of the spectrum,’ said Mona Jarrahi, a professor of electrical and computer engineering at the University of California, Los Angeles (UCLA), who led the research. ‘In astronomy, the advantage of the terahertz range is that, unlike infrared and visible light, terahertz waves are not obscured by interstellar gas and dust that surround astronomical structures.’

The system produces images in ultra-high clarity, and is capable of identifying the spectral signatures of elements and molecules — for example, water, oxygen, carbon monoxide and other organic molecules – present in the regions of space it observes. It could therefore aid scientists in learning more about the composition of astronomical objects and structures, and the physics of how they form and die. The technology could also help answer questions about how such objects and structures interact with the gases, dust and radiation that exists between stars and galaxies, and reveal clues about the cosmic origins of water or organic molecules that could indicate whether a planet is hospitable to life.

The system could also be used on Earth to detect harmful gases for security or environmental monitoring purposes, according to the researchers.

No need for coolant

The key to the new system is how it converts incoming terahertz signals, which are not easy to sense and analyse with standard scientific equipment, into radio waves that are easy to handle.

Existing systems use superconducting materials to translate terahertz signals to radio waves. But to work, those systems use specialised liquid coolant to keep those materials at extremely low temperatures, approaching absolute zero. Supercooling the equipment is feasible on Earth, but when the sensors are taken on spacecraft, their lifespans are limited by the amount of coolant aboard. Also, because spacecrafts’ weight is so important, it can be problematic to carry the extra pounds of coolant the equipment needs.

The UCLA researchers therefore created a new technology to address the coolant and related weight issues. Their device uses a beam of light to interact with the terahertz signals inside a semiconductor material with metallic nanostructures. The system then converts the incoming terahertz signal into radio waves, which are read by the system and can be interpreted by astrophysicists. The new technology therefore enables the detection of terahertz radiation across a broad spectral using equipment operating at room temperature, rather than close to absolute zero.

The researchers' work was supported by the Jet Propulsion Laboratory’s (JPL’s) Strategic University Research Partnership programme, the US Department of Energy, the Office of Naval Research and the National Science Foundation.

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