Lasers and THz Waves Combined in Hyperspectral Camera

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SUSSEX, England, Feb. 19, 2020 — A team of physicists at the University of Sussex has developed the first nonlinear camera capable of capturing high-resolution images of the interior of solid objects using terahertz (THz) radiation.

Led by Marco Peccianti of the Emergent Photonics (EPic) Lab, Luana Olivieri, Juan S. Totero Gongora, and a team of research students built a new type of THz camera capable of detecting THz electromagnetic waves with high accuracy.

Images produced using THz radiation are called hyperspectral because the image consists of pixels, each one containing the electromagnetic signature of the object in that point.

Lying between microwaves and infrared in the electromagnetic spectrum, THz radiation penetrates materials like paper, clothes, and plastic in the same way x-rays do, but without harmful consequences. THz imaging allows for the observation of the molecular composition of objects and distinguishes between different materials.

“The core challenge in THz cameras is not about collecting an image, but it is about preserving the object’s spectral fingerprint that can be easily corrupted by your technique,” Peccianti said. “This is where the importance of our achievement lies. The fingerprint of all the details of the image is preserved in such a way that we can investigate the nature of the object in full detail.”

The EPic Lab researchers used a single-pixel camera to image sample objects with patterns of THz light. The prototype they built can detect how the object alters different patterns of THz light. By combining this information with the shape of each original pattern, the camera reveals the image of an object as well as its chemical composition.

The Sussex team shined a standard laser onto a unique nonlinear material capable of converting visible light to THz. The prototype camera creates THz electromagnetic waves close to the sample, similar to how a microscope works. As THz waves can travel right through an object without affecting it, the resulting images reveal the shape and composition of objects in three dimensions.

“This is a major step forward because we have demonstrated that all the possibilities explored in our previous theoretical research are not only feasible, but our camera works even better than we expected,” Gongora said. “While building our device, we discovered several ways to optimize the imaging process, and now the technology is stable and works well.”

Gongora said that the next phase of his team’s research will involve speeding up the image reconstruction process and getting closer to applying THz cameras to real-world applications, such as airport security, intelligent car sensors, quality control in manufacturing, and scanners to detect health problems like skin cancer.

Published: February 2020
terahertz radiation
Electromagnetic radiation with frequencies between 300 GHz and 10 THz, and existing between regions of the electromagnetic spectrum that are typically classified as the far-infrared and microwave regions. Because terahertz waves have the ability to penetrate some solid materials, they have the potential for applications in medicine and surveillance.
Research & TechnologyEuropeUniversity of Sussexterahertz radiationelectromagnetic waveshyperspectralx-rayscamerasImagingLasersterahertz cameras

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