Ricerc@Sapienza

One of the most innovative aspects of a spectroscopic imaging system, based on a QCL THz source, resides in the typical output powers in the milliwatt range that it is about three magnitude orders higher than other THz sources emitting at the same frequency. This important characteristic makes it possible to perform faster image acquisition even with slow thermal detectors (such as pyroelectric, or bolometer) and to achieve higher SNR. Also, the deep penetration of the THz radiation, combined with its strong water absorption, offers great potential in many fields of interest for the scientific community (e.g. biomedical, cultural-heritage, environmental, agri-food).
From the imaging point of view, at 3 THz, the diffraction resolution is limited to about 100 µm and the beam waist is typically around a few hundred microns allowing for non-destructive applications the detection of slight defects, while the small beam size improves the measurements on highly curved surfaces. Moreover, the refractive-index contrast in the THz range makes it easier to detect different layers (thickness THz imaging spectrometer, equipped with high power QCL source, together with cameras based on microbolometer technology that offer a noise equivalent powers (NEP) in the order of tens of pW, are also opening up the way to perform real-time spectroscopic imaging thus immediate material mapping will become possible. This is very important for fast identification of experimental interest regions during field measurements, monitoring restoration processes and for observing dynamic deterioration.
The Sapienza Terahertz project will involve as many as 16 Departments, incorporating many different applications in biomedicine, biology, chemistry, environment, food quality and safety, cultural heritage, physics, engineering, electromagnetic compatibility (EMC), material science and nanotechnology.
At the environmental level, one of the latest trends is to expand analytical strategies to monitor air, water and soil pollution as well as phenomena related to global climate change, such as the aridity increasing in many regions worldwide. Most of the conventional monitoring techniques are limited by the time, expensiveness and high result variability. Thus, reliable and fast technique such as THz spectroscopy (THz-S) has a promising potential to identify and quantify environmental stressors. Recently, THz-S has been used to measure PM2.5 concentration in air and to characterize pollutant sources [2]. THz-S is also suitable to analyze proximal soil characteristics [3], providing direct measurements in situ and multi-parametric information. Compared to other techniques, THz has the additional advantage to perform non-destructive and continuous in vivo determinations of plant water status, revealing very small water status changes and not being affected by the plant inorganic salt content [3]. This offers the possibility to select cultivars more resistant to water stress and to determine the maturity stages of fruits and vegetables correlating plant water status and horticultural attributes.
As far as food quality and safety is concerned, modern research is moving from classical methodologies to advanced comprehensive analytical strategies. THz-S has a great potential for agri-food process monitoring and quality control in real-time. Moreover, it can be used to recognize foreign bodies, to determine contaminants in agri-food products, to characterize edible oils and genetically modified food [4].
Nowadays, there is a growing interest in THz technology applied to wireless communications systems (WCS). In fact THz technology can meet the 5G WCS network capacity requirements. Thus, the design, characterization and fabrication of protection systems against THz EM interference is one goal of actual EMC research. In particular, graphene based EM screen [5,6] are opening new opportunities compared to the current solutions based on carbon-filled nanocomposites or on thin-film technology.
Most of low-energy excitations in condensed matter fall in the THz range e.g the superconducting gap, soft phonon modes, polar modes in ionic liquids, excitations in magnetic systems. These could be studied at SapienzaTerahertz both through spectroscopy and imaging. This provides the possibility to investigate new materials for photonics and electronics.

[1] K. Fukunaga. Springer Japan, 2016.
[2] H. Zhan et al, J. Infrared, Millim Terahertz Waves, 37, 929, 2016.
[3] Dworak et al., Sensors, 17(10), 2387.
[4] Gowen et al., Food science and technology, 25,40, 2012
[5] Su, Zengping, et al. Physical Chemistry Chemical Physics 20(21), 14357, 2018
[6] Xu, Z., et al, Nanoscale research letters, 13(1), 143, 2018