Researchers develop device that can detect terahertz frequencies in deep space

UCLA researchers have developed a novel light-detecting device which could be used in space exploration.

A paper detailing this technological development was published July 8 in Nature Astronomy. Mona Jarrahi, a professor of electrical engineering, created the device with her research team at UCLA. Unlike similar devices, this device does not require expensive equipment to regulate temperature. Its smaller size, lack of bulky coolant, and cost-effectiveness makes it ideal for space exploration, Jarrahi said.

The device’s sensors detect terahertz frequencies, which are converted into electrical charges using visible light. The use of light allows the device to operate at room temperature, unlike other products which also detect terahertz frequencies. Terahertz frequencies are waves, like visible light or radio waves, whose wavelengths range from one millimeter to 0.1 mm – longer than the wavelengths of visible light.

This electric current can then be amplified and help researchers detect what types of molecules generated the terahertz waves. The use of visible light allows the device to operate at room temperature and eliminates the need for an additional cooling system.

The new device is especially useful for detecting molecules and gases in space due to its high sensitivity, said Semih Cakmakyapan, co-lead author of the study and former postdoctoral student at UCLA. Cakmakyapan said the device can determine the chemical composition of even small amounts of gases.

“We don’t need to have a lot of gases or material (in order to detect a substance) because we have a very sophisticated product,” he said.

The main components of the device include lasers used to generate photons, or particles of light, and a chip that is approximately a square millimeter in size – almost the size of a grain of sand. The sensor uses photons to convert radiation at terahertz frequencies into electric current at radio frequencies. The sensor uses these currents to determine which molecules are present in outer space.

Ning Wang, co-lead author of the study and former UCLA researcher, said terahertz waves are particularly useful for studying distant molecules because many materials have unique spectral “fingerprints” in the terahertz range. Unlike visible light, terahertz waves can penetrate into some opaque objects, meaning that terahertz can “see through” these materials. Being able to sense terahertz waves can give us a better understanding of what molecules make up the universe.

“Most molecules have a very unique signal in terahertz frequency,” Jarrahi said.

Wang said their research paper has proven the device’s extreme sensitivity and ability to detect weak signals, as it is sensitive enough to detect just a single photon.

Wang said she believes the detectors have the greatest potential for use in space exploration where there is less interference. Unlike Earth’s atmosphere, outer space does not contain significant air or water particles that could absorb terahertz frequencies.

“Outer space is the perfect environment to study terahertz waves,” Wang said.

In addition to space exploration, the device may have many practical uses on Earth, Jarrahi said. The system may be able to detect harmful substances in security systems due to its ability to detect terahertz frequencies through opaque objects, such as suitcases. The sensors may also be used to detect environmental pollution, she said.

The detector may also be used in medicine, added Cakmakyapan. Because it examines terahertz waves, the device is less invasive and damaging than current medical technologies that use X-rays or ultraviolet rays.

“It’s not dangerous, which is very important, whereas ultraviolet waves may cause cancer,” Cakmakyapan said.

Doctors may also use the device to examine patients by detecting the gases present in one’s breath, Jarrahi said. For example, the presence of ammonia may signal kidney disease.

For the next step, astrophysicists are looking to deploy these sensors on a telescope with NASA. They would be used to detect some of the important signatures of astronomy-relevant chemicals on Earth, Jarrahi said.