The aim of the project is to develop a system capable of enabling true terahertz hyperspectral imaging at unprecedented rates. The best performing terahertz spectral imagers nowadays are based on raster scanning, i.e. performing a single pixel spectral analysis and moving the sample, which makes the process time-consuming and, hence, not suitable for most industrial applications. Conversely, the approach proposed here is based on a sophisticated dual-comb terahertz radiation source that illuminates the target area enabling the direct characterisation the spectral response of a sample simultaneously at every pixel of the image and at a rate that is orders of magnitude faster than any other comparable system.
Terahertz spectroscopy has already demonstrated very promising advantages for the food and agricultural industries, with a variety of applications that range from the detection of harmful residues or microorganisms to quality classification. Besides this, there are many other feasible applications, to mention a few, in the pharmaceutical industry, the semiconductors sector, or, with an adequate development, biomedical research. In addition, terahertz radiation is non-ionizing so no special personal protection equipment or policies are needed for its use.
To fully take advantage of all the opportunities that terahertz spectroscopy provides for enhancing the efficiency of industrial processes, systems with the ability of performing hyperspectral imaging instead of single point analysis are required. Nevertheless, the lack of maturity of current terahertz hyperspectral technology has hindered the deployment of these systems beyond research laboratories. The imager to be developed during this project automatically transforms any terahertz camera into a fast terahertz hyperspectral detector, completely redefining the performance of current systems and overcoming previous limitations. This gigantic boost in capabilities could be the last straw in pushing the encouraging terahertz technology towards an intermediate-term widespread use in industry.
A photonic-based approach will be adopted to implement a dual terahertz frequency comb source (a technology that has already revolutionized optical spectroscopy) that enables the straightforward reading and detection of the terahertz spectral information. This advanced absolute-frequency terahertz generator, with widely tunable frequency range and resolution, consists of an utterly stabilised dual terahertz frequency comb with a perfectly phase-locked comb to comb frequency difference of a few hertz. The spectral information that is inscribed by the sample into the terahertz combs can therefore be squeezed into the range of frequencies below 12.5 Hz. This makes possible for any regular video-rate (25 frames per second) terahertz camera to read the hyperspectral image at the same time in all pixels, enabling true terahertz hyperspectral imaging for the first time.