Feb 19 2020
At the University of Sussex, a group of physicists has been successful in creating the first nonlinear camera that uses terahertz (THz) radiation to capture high-resolution images of the interior of solid objects.
The time-resolved nonlinear ghost imaging camera uses a nonlinear crystal to convert standard laser light to terahertz patterns, allowing the reconstruction of complex samples using a single terahertz pixel. Image Credit: University of Sussex.
Luana Olivieri, Dr Juan S. Totero Gongora, and a group of research students headed by Professor Marco Peccianti of the Emergent Photonics (EPic) Lab developed a new kind of THz camera with the ability to detect THz electromagnetic waves with unmatched accuracy.
Images captured using THz radiation are termed “hyperspectral” since the image includes pixels. Each pixel contains the electromagnetic signature of the object at that point.
In the electromagnetic spectrum, the THz radiation lies between infrared and microwaves, and can easily penetrate into materials such as clothes, plastic, and paper, quite similar to X-rays, but without causing any damage.
It can be safely used even for the most sensitive biological samples. THz imaging enables the observation of the molecular composition of objects and differentiating between two distinct materials, for example, differentiating cocaine from sugar.
The core challenge in THz cameras is not about collecting an image, but it is about preserving the objects spectral fingerprint that can be easily corrupted by your technique. 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.
Marco Peccianti, Professor, Emergent Photonics Lab, University of Sussex
Prof Peccianti thus explained the importance of their achievement. To date, cameras with the ability to capture a hyperspectral image that retains all the fine details divulged by THz radiation had been regarded as impossible.
A single-pixel camera was used by the researchers at the EPic Lab to image sample objects with patterns of THz light. The prototype developed by the team has the ability to detect how the object modifies various patterns of THz light. The camera combines this information with the shape of each original pattern to reveal the image of an object together with its chemical composition.
THz radiation sources are extremely faint, and to date, hyperspectral imaging had low fidelity. The Sussex researchers solved this issue by shining a typical laser onto an exclusive non-linear material that has the ability to convert visible light to THz.
Just like the operation of a microscope, the prototype camera produces THz electromagnetic waves very near to the sample. THz waves have the potential to penetrate right through an object without causing any damage; thus, the ensuing images unravel 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. While building our device, we discovered several ways to optimise the imaging process and now the technology is stable and works well.
Dr Juan S. Totero Gongora, Researcher, Emergent Photonics Lab, University of Sussex
Dr Totero Gongora concluded saying, “The next phase of our research will be in speeding up the image reconstruction process and taking us closer to applying THz cameras to real-world applications; like airport security, intelligent car sensors, quality control in manufacturing and even scanners to detect health problems like skin cancer.”