Imaging with terahertz radiation

Abstract

Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies.

Detailed non-destructive evaluation of UHMWPE composites in the terahertz range

“…Terahertz (0.1-3.0 THz) imaging is novel visualization technique which can serve in many application areas, like detecting explosives and related compounds (Chan et al 2007), identifying various defects (Lopato et al 2009), tomography and materials identification and characterization (Mittleman et al 1999) or detecting contaminations (Wietzke et al 2007). Electromagnetic waves in the range of 0.1-3.0 THz has an unique ability to penetrate many materials, which are opaque in the range of visible and infrared light, thus enabling visualization of their internal structure.…”

“…The THz time domain spectroscopy (TDS) is the most commonly used method from all THz techniques for non-destructive evaluation of composite materials (Chan et al 2007;Lopato et al 2009;Mittleman et al 1999;Wietzke et al 2007). Although other techniques based on a FMCW radar (Quast et al 2010) as well as CW imaging by means of quantum cascade lasers (Destic et al 2010), a gas laser (Redo-Sanchez et al 2006) or with a Gunn diode (Karpowicz et al 2005) were also studied.…”

Room-temperature two-color lasing by current injection into a GaAs/AlGaAs coupled multilayer cavity fabricated by wafer bonding

“…1,2) The generation of ultrashort THz pulses has been extensively developed for time-domain spectroscopic applications based on recent femtosecond-laser technologies. [3][4][5] Several types of continuous-wave THz emitters have also been studied and developed using semiconductor technologies.…”

Ultra low bending loss equiangular spiral photonic crystal fibers in the terahertz regime

“…1 This has led to a concerted research effort in the area of THz sources, detectors and waveguides and for the successful implementation of THz systems, low loss and commercially viable waveguides are essential.…”