THz – TDS

Terahertz time-domain spectroscopy (THz-TDS) is an advance NON-DESTRUCTIVE TESTING (the radiation in the Terahertz does not have sufficient energy to ionize the target molecules, unlike what happens for example for the X radiation) that relies on the generation and detection of photons with a frequency in the THz range (f ∼ 10¹² Hz, T∼ ps = 10^-12 s) to probe the characteristics of the material under investigation.

To study a material, a THz pulse can be sent towards the sample to analyze by a scanning system the radiation passing through or reflected by the crystal lattice structure. The application that can be carried out for the architectural art and building materials are for example: imaging of cracks and cracking, water diffusion, detection of internal void and defects, orientation of fibers, difference in the chemical composition (E.g., presence and quantification of chloride ion in concrete). In addition to solid state samples, liquid substances and powders can also be tested. Furthermore, this technique can be even more interesting by comparing the results with those of the other analysis techniques we use in our laboratories, i.e., acoustic emissions, ultrasonic tests, optical microscopy analyses and Digital Image Correlation.

Inside the laboratory of “Sistemi Edilizi” (DISEG), in a dedicated environment with controlled temperature and relative humidity, you will find the following equipment for the THz-TDS:

TeraSmart

Compact terahertz spectrometer by Menlo Systems with integrated: femtosecond laser source, optical delay unit (ODU) and ADC unit. The system mount prealigned THz optics based on off axis parabolic mirrors (OAPM) on 30×30 cm breadboard. TeraSmart can reach over 6 THz bandwidth in 5 s, >100 dB of Dynamic Range, THz frequency resolution up to 1.2 GHz and a flexible scan speed (> 850 ps).

Tera Image (upgrade for TeraSmart)

An automated imaging unit by Menlo Systems mounted on TeraSmart which can acquire THz images, in transmission or reflection geometry, containing the entire spectral information for each data pixel of the scanned X-Y-plane with a dimension of 150 x 150 mm. For larger objects, more images can be scanned and then merged together.

Reflection head (upgrade for TeraSmart)

A compact and alignment-free device by Menlo Systems mounted on TeraSmart which can perform reflection measurements without compromise in the performance (>95 dB, > 6THz) for bigger sample without geometric constraints.

ImageLab

Dedicate computer with ImageLab®, a hyperspectral Image Processing Software by Menlo System for THz Imaging Data. The software can also perform analysis of data from various spectroscopic imaging techniques such optical, UV/VIS, IR, Raman, or mass spectrometry.