Abstract-Hyperspectral terahertz imaging with electro-optic dual combs and a FET-based detector

Pedro Martín-Mateos, Dovilė Čibiraitė-Lukenskienė, Roberto Barreiro, Cristina de Dios, Alvydas Lisauskas, Viktor Krozer,  Pablo Acedo

https://www.nature.com/articles/s41598-020-71258-6

In this paper, a terahertz hyperspectral imaging architecture based on an electro-optic terahertz dual-comb source is presented and demonstrated. In contrast to single frequency sources, this multi-heterodyne system allows for the characterization of the whole spectral response of the sample in parallel for all the frequency points along the spectral range of the system. This hence provides rapid, highly consistent results and minimizes measurement artifacts. The terahertz illumination signal can be tailored (in spectral coverage and resolution) with high flexibility to meet the requirements of any particular application or experimental scenario while maximizing the signal-to-noise ratio of the measurement. Besides this, the system provides absolute frequency accuracy and a very high coherence that allows for direct signal detection without inter-comb synchronization mechanisms, adaptive acquisition, or post-processing. Using a field-effect transistor-based terahertz resonant 300 GHz detector and the raster-scanning method we demonstrate the two-dimensional hyperspectral imaging of samples of different kinds to illustrate the remarkable capabilities of this innovative architecture. A proof-of-concept demonstration has been performed in which tree leaves and a complex plastic fragment have been analyzed in the 300 GHz range with a frequency resolution of 10 GHz.

Abstract-Terahertz hyperspectral imaging with dual chip-scale combs

Lukasz A. Sterczewski, Jonas Westberg, Yang Yang, David Burghoff, John Reno, Qing Hu, Gerard Wysocki

https://arxiv.org/abs/1812.03505

Hyperspectral imaging is a technique that allows for the creation of multi-color images. At terahertz wavelengths, it has emerged as a prominent tool for a number of applications, ranging from non-ionizing cancer diagnosis and pharmaceutical characterization to non-destructive artifact testing. Contemporary terahertz imaging systems typically rely on non-linear optical down-conversion of a fiber-based near-infrared femtosecond laser, requiring complex optical systems. Here, we demonstrate hyperspectral imaging with chip-scale frequency combs based on terahertz quantum cascade lasers. The dual combs are free-running and emit coherent terahertz radiation that covers a bandwidth of 220 GHz at 3.4 THz with ~10 μW per line. The combination of the fast acquisition rate of dual-comb spectroscopy with the monolithic design, scalability, and chip-scale size of the combs is highly appealing for future imaging applications in biomedicine and in the pharmaceutical industry

Abstract-Measurement of agricultural products using terahertz hyperspectral imaging

Krunal Radhanpura,   David Farrant,  Jia Du

http://ieeexplore.ieee.org/document/8066930/

Terahertz Spectroscopy can be used as a non-destructive testing method for qualitative analysis of food and agricultural products. In this paper we report on the progress of developing a terahertz hyperspectral imaging system and its applications in the safety and quality control of food and agricultural products.