Sensing with Terahertz Radiation

Sensing with Terahertz Radiation reviews the state of the art in the generation, manipulation, and detection of electromagnetic radiation in the terahertz range. Recent years have seen a tremendous growth in research and development efforts in this spectral regime, spanning roughly from 0.3 THz to 10 THz. This has been spurred in part by several startling advances, involving non-linear optical materials, ultrafast optical and electronic techniques, and spectroscopic methods. As a result, there have been qualitative and significant improvements in the generation and detection of THz radiation. These have enabled a number of "real world" applications of THz technologies, in a manner which would not have been practical only a few years ago. A number of demonstrations and feasibility tests are discussed, which serve as compelling evidence of the utility of such techniques. Owing to the unique characteristics of THz radiation and its interactions with materials, these methods can have substantial advantages over other more conventional technologies. This text includes contributions on topics including time-domain spectroscopy based on both photoconductive and electro-optic sampling, photomixing, and all-electronic THz generation. advantages over other, competing technologies in a number of different areas. One aspect of the field of THz radiation is the marriage of microwave and optical techniques. By its very nature, THz radiation bridges the gap be­ tween the microwave and optical regimes. The former can be characterized by the fact that most devices are comparable in size to the wavelength of the radiation. As a result, the propagation of energy in these devices is generally in the form of single-mode or low-order-mode guided waves. In contrast, the optical and infrared ranges are generally characterized by beams containing many modes, with dimensions much larger than the wavelength. Of course, there are exceptions to these rules, notably the single-mode propagation of optical radiation in fibers. Nonetheless, the general description holds true. Because of these fundamental differences, it is natural that the techniques used in their implementation are quite distinct. Much of the research in the THz field has been based on the melding of these disparate ideas.

The purpose of this book is two-fold. First, the various different methods of accessing the THz range are discussed, with a view to convince the reader that there have been qualitative and significant improvements over older, more conventional techniques. The text makes it clear that these improvements enable practical real-world applications of THz technology, in a manner which would not have been possible before. Second, the demonstrations and feasibility tests described serve as compelling evidence of the utility of such devices. Due to the unique characteristics of THz radiation and its interaction with materials, these devices have substantial advantages over other competing technologies in a number of different areas.

Front Matter....Pages I-XVI Introduction....Pages 1-38 Spectroscopy in the Terahertz Spectral Region....Pages 39-115 Terahertz Imaging....Pages 117-153 Free-Space Electro-Optic Techniques....Pages 155-192 Photomixers for Continuous-Wave Terahertz Radiation....Pages 193-236 Applications of Optically Generated Terahertz Pulses to Time Domain Ranging and Scattering....Pages 237-293 Bio-medical Applications of THz Imaging....Pages 295-316 Electronic Sources and Detectors for Wideband Sensing in the Terahertz Regime....Pages 317-334 Back Matter....Pages 335-339 Introduction (Grischkowsky/Mittleman) Spectroscopy in the Terahertz Spectral Region (De Lucia) Terahertz Imaging (Mittleman) Free Space Electro-Optic Techniques (Jiang/Zhang) Photomixers for Continuous-Wave Terahertz Radiation (Duffy/Verghese/Mc Intosh) Applications of Optically Generated Terahertz Pulses to Time Domain Ranging and Scattering (Cheville/Reiten/McGowan/Grischkowsky) Bio-medical Applications of Terahertz Imaging (Koch) Electronic Sources and Detectors for Wideband Sensing in the Terahertz Regime (Van der Weide).