New Type of a Terahertz Camera

Using a single-pixel camera and terahertz electro­magnetic waves, a team of physicists at the Univer­sity of Sussex have devised a blueprint which could lead to the develop­ment of airport scanners capable of detecting explosives. Luana Olivieri and Juan Sebastian Totero Gongora of the Emergent Photonics Lab directed by Marco Peccianti and Alessia Pasquazi, have found an inno­vative way to capture with high accuracy, not just the shape of an object, but also its chemical compo­sition using a special “single point” camera capable of operating at terahertz fre­quencies.

Illustration of the concept of time-resolved nonlinear ghost imaging. (Source: Univ. of Sussex / ACS Photonics)

Totero Gongora said: “Our approach produces a new type of image which is quite different from what you would get from a standard single-pixel camera as it provides much more information on the object. Compared to prior single pixel images, we also demon­strated that our resolution is inhe­rently higher.” Terahertz radiation can easily penetrate several common materials like paper, clothes and plastics leading to the develop­ment of technology within security scanning and manufacture control which allows people to see inside objects and wrapping. The radiation provokes a different response from bio­logical samples though, allowing researchers to classify materials which are almost indistin­guishable with visible light.

Scientists believe that terahertz waves could have enormous potential in developing critical appli­cations such as explosives detection, medical diag­nostics, quality control in manu­facturing and food safety. The challenge, however, lies in the development of reliable and cost-effective cameras as well as the ability to identify objects smaller than the wavelength. But, by taking a different approach to previous studies in this field, the team of the Emergent Photonics Lab may have found a way to overcome these limi­tations. While previous research has illu­minated objects with many patterns of laser light in just one colour to extract an image, the researchers illu­minated an object with patterns of terahertz light which contain a broad spectrum of colours.

A single pixel camera can capture the light reflected by the object for each pattern. In the team’s study, they found that the camera can detect how the pulse of light is altered in time by the object even if the pulse is an extremely short event. By combi­ning this infor­mation with the known shape of the patterns, the shape of the object and its nature are revealed. The technique may recall the way the brain develops under­standing in the vision by focusing sepa­rately on different elements and then fusing the relevant information.

Peccianti added: “This is a really signi­ficant development. Previous approaches to terahertz single-pixel cameras cannot preserve the complete infor­mation on an object but we under­stood where the issue lay and identified a way to extract a more complete image. We hope that a similar system to ours could be used in real-life appli­cations in biology, medicine and security to determine the chemical compo­sition of an object and its spatial distri­bution in just one step.”

The team’s findings are a consi­derable improve­ment on established tech­nologies and could have a huge impact beyond the field of terahertz cameras. For instance, their technique could be used to design high-reso­lution cameras in other frequency ranges which could then become part of tech­nology for collision sensors, body scanner or ultra-rapid radars for self-driving cars. The researchers are now following up on their research, which is largely based on simulations, to experi­mentally demonstrate their device. (Source: Univ. Sussex)

Reference: L. Olivieri et al.: Time-Resolved Nonlinear Ghost Imaging, ACS Phot. 5, 3379 (2018); DOI: 10.1021/acsphotonics.8b00653

Link: Emergent Photonics Lab, University of Sussex, Brighton, UK

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