Towards Practical Terahertz Imaging System With Compact Continuous Wave Transceiver

Abstract

Terahertz (THz) imaging techniques have attracted significant attention and have developed rapidly in recent years. However, despite several advances, these techniques are still not mature, and their high cost and system complexity continue to limit their applications. In this article, the techniques for achieving a practical imaging system with a compact THz transceiver are addressed, while considering the limitations of the current technique. The aim is to provide a brief review of related topics, while also covering our recent progress, which can provide some general perspectives and contrasting approaches for realizing a practical THz imaging system. The continuous wave devices are mainly focused for their flexibility of balancing the imaging resolution and data acquisition time. The importance of transceiver integration is also discussed and illustrated by introducing a 600-GHz band micro-photonic interface for integrating a THz source and detector, with a single resonant tunneling diode as a transceiver. With regard to system issues, spatial sampling with mechanical beam-scanning is discussed as an intermediate approach for moving stage and array technology. The potential and limitations of this approach are evaluated, along with an elliptical reflector as an alternative to an f-theta lens owing to its low cost and simplicity. The combination of integrated devices, along with the mechanical beam-scanning, is also discussed for demonstrating our current concept of realizing a practical THz imaging system.

Photonic Radar for 3D Imaging: From Millimeter to Terahertz Waves

“…Compared with the established imaging instruments and techniques, novel imaging systems in higher frequency bands, such as the millimeter wave (MMW, 30-100 GHz), sub-terahertz (sub-THz, 0.1-0.3 THz), and THz (0.3 THz-10 THz) bands, have attracted significant attention, as these frequencies lead to considerably improved spatial resolution due to their higher frequencies and wider bandwidths. For example, THz band imaging systems have demonstrated submillimeterlevel resolution and transparency for electrical insulators such as paper, glass, and polymers [2], [3], [4], [5]. More importantly, these frequency bands can be used for wireless communication and industrial applications since they do not harm the human body.…”

Ultra-Wideband Frequency Modulated Continuous Wave Photonic Radar System for Three-Dimensional Terahertz Synthetic Aperture Radar Imaging

“…The down-converted optic signal permits an ultra-wide bandwidth, fast frequency sweep, and reduced phase noise. Although THz pulse signal can be directly obtained with photonics-based devices, the synthesized pulse obtained with CW radar and/or swept-source optical coherence tomography (SS-OCT) techniques can provide higher power with a simpler system [1], [8], [23]. Owing to the fast frequency sweep speed in the optic domain, the frequency-modulated 2 > REPLACE THIS LINE WITH YOUR MANUSCRIPT ID NUMBER (DOUBLE-CLICK HERE TO EDIT) < continuous-wave (FMCW) technique is considered a promising method for fast 3D imaging systems in the THz band [24]- [28].…”

Design and Characterization of Wideband Terahertz Metamaterial Stop-Band Filter

“…The unique electromagnetic (EM) response generated by metamaterials is particularly valuable in the terahertz state, where most naturally occurring materials exhibit a weak EM response to terahertz waves. The terahertz region, typically defined between 0.1 and 10 THz, remains the least developed region of the EM spectrum due to the lack of effective terahertz sources, detectors and functional devices, and the advent of metamaterials is expected to narrow the “terahertz gap” [ 6 , 7 , 8 ].…”