A practical guide to terahertz imaging using thermal atomic vapour

Abstract

This tutorial aims to provide details on the underlying principles and methodologies of atom-based terahertz imaging techniques. Terahertz imaging is a growing field of research which can provide complementary information to techniques using other regions of the electromagnetic spectrum. Unlike infrared, visible and ultraviolet radiation, terahertz passes through many everyday materials, such as plastics, cloth and card. Compared with images formed using lower frequencies, terahertz images have superior spatial resolution due to the shorter wavelength, while compared to x-rays and gamma rays, terahertz radiation is non-ionising and safe to use. The tutorial begins with the basic principles of terahertz to optical conversion in alkali atoms before discussing how to construct a model to predict the fluorescent spectra of the atoms, on which the imaging method depends. We discuss the practical aspects of constructing an imaging system, including the subsystem specifications. We then review the typical characteristics of the imaging system including spatial resolution, sensitivity and bandwidth. We conclude with a brief discussion of some potential applications.

Numerical model of N-level cascade systems for atomic RF sensing applications

“…Rydberg RF sensors have been shown to be SI traceable and provide a self-calibrated solution for electrometers [1]. Further to the electrometers Rydberg sensors have been used for RF, mm Wave imaging [2] and Wireless communications [3].…”

“…This potential for an increase in sensitivity below that of the thermal noise floor has gained interest from communication engineers with a new focus on atom-based RF communication using both analogue and digital encoding [3,[10][11][12]. Furthermore, this technology has been developed for the purpose of RF imaging in the terahertz regime [2,13], with applications ranging from building inspection to RF environment tracking. Both the amplitude and phase of a weakly modulated RF field [3,14] can be detected at higher modulation rates limited only by the relaxation time of the atom.…”