Spectroscopic Terahertz Imaging at Room Temperature Employing Microbolometer Terahertz Sensors and Its Application to the Study of Carcinoma Tissues

Abstract

A terahertz (THz) imaging system based on narrow band microbolometer sensors (NBMS) and a novel diffractive lens was developed for spectroscopic microscopy applications. The frequency response characteristics of the THz antenna-coupled NBMS were determined employing Fourier transform spectroscopy. The NBMS was found to be a very sensitive frequency selective sensor which was used to develop a compact all-electronic system for multispectral THz measurements. This system was successfully applied for principal components analysis of optically opaque packed samples. A thin diffractive lens with a numerical aperture of 0.62 was proposed for the reduction of system dimensions. The THz imaging system enhanced with novel optics was used to image for the first time non-neoplastic and neoplastic human colon tissues with close to wavelength-limited spatial resolution at 584 GHz frequency. The results demonstrated the new potential of compact RT THz imaging systems in the fields of spectroscopic analysis of materials and medical diagnostics.

Influence of Field Effects on the Performance of InGaAs-Based Terahertz Radiation Detectors

“…Here, µ 0 is the low-field mobility; v sat is the electron saturation velocity; F is the driving force for the charge carriers, which is the absolute value of the electric field in the simplest case and the absolute value of the gradient of a quasi-Fermi potential in our calculations; and α and β are the parameters that are adjusted to fit the experimental data. The µ(E) dependence for InGaAs was obtained by fitting the experimental data reported in [18] using formula (2), as shown in Fig. 9 (left), with the following parameters: µ 0 = 8500 cm 2 V −1 s −1 , v sat = 2.9 · 10 7 cm/s, α = 0, and β = 40.…”

“…operating concepts have been tested, which are used in, for example, Schottky detectors [1], microbolometer arrays [2], semiconductor field-effect transistors (FETs) with nanometric gates [3][4][5][6], and bow tie (BT)-shaped semiconductor diodes [7][8][9].…”

Compact diffractive optics for THz imaging

“…The comparison of the metal zone plate and commercial parabolic mirror focusing performance was presented in [4]. It was shown that the imaging system with the 5 mm focal length zone plate improves the spatial resolution up to 25% in comparison with that of a commercial parabolic mirror.…”

“…It was shown that the imaging system with the 5 mm focal length zone plate improves the spatial resolution up to 25% in comparison with that of a commercial parabolic mirror. Using the same experimental set up, presented in [4], the resolution target imaging using the 50 mm diameter THz MPFL is recorded. The imaging result of the resolution target and the plastic card containing an USB stick is shown in Fig.…”

“…It can be assumed that development of compact THz diffractive optics components, which enable massive parabolic mirrors to be replaced by much more attractive flat compact optical elements, is a particularly important issue [4,5].…”