Agilent Measurement Journal - Issue 4 - 2008 - (Page 53)

T Introduction: Why terahertz? The terahertz part of the electromagnetic spectrum has four important characteristics that make it particularly interesting. First, wave propagation at these frequencies is very strongly affected by the presence of water. This could make terahertz useful for very short-haul secure communications. It also enables a large contrast between materials with different moisture content. A great example of the usefulness of this property is in the detection of cancerous tissues. Cancer tumors grab onto blood vessels (vascularize) to feed their rapid growth. As a result, they have much higher moisture content than normal surrounding tissues and easily can be detected. Second, many solid materials have unique phonon resonances in the terahertz range. This leads to the ability to use spectroscopy to identify materials with high conﬁdence. Examples include the detection of a range of plastic explosives and of different crystal forms (polymorphs) of pharmaceutical compounds. The latter is important for detecting counterfeit drugs and for protecting a company’s intellectual property. Third, many gas molecules have rotational moments at terahertz that lead to rapid identiﬁcation with spectroscopy. Fourth, the penetration of terahertz radiation into materials makes it suitable for many imaging applications. For example, new applications are emerging in nondestructive inspection of semiconductors, pharmaceutical compounds and medical diagnostics. In each case, the unique spectral response of materials to terahertz radiation reveals features that are difﬁcult or impossible to see in any other frequency range. Resolution can be improved by using near-ﬁeld techniques such as those discussed below. This approach will open even more exciting applications. The portion of the electromagnetic spectrum between the microwave and millimeter region (109 to 1011 hertz) and the infrared (IR) and optical region (1013 to 1015 hertz) is characterized by a lack of emitters and detectors capable of enabling useful measurements. The reason is that the electronic devices used at microwave frequencies are very difﬁcult to extend up in frequency and the optical ones used at IR and optical frequencies are hard to extend down in frequency. The popular name for this part of the spectrum is “terahertz” (0.1 to 10 THz). Interest in terahertz is accelerating since many materials exhibit unique terahertz frequency-range properties that provide high contrast for imaging and spectroscopic materials identiﬁcation. There also is a need for measurement equipment to be expanded into the terahertz region not only to support these applications but also to measure devices that, due to Moore’s law, are rapidly pushing up toward 1 THz and beyond. For many years, Leeds University has performed some of the world’s best research in terahertz. In the past ﬁve years its program has expanded to include involvement with most aspects of the terahertz research going on around the world. As a leading provider of microwave, millimeter wave and IR/optical measurement equipment, Agilent Technologies is supporting some of this research with an eye toward expanding our measurement coverage into this area — and exploring new possibilities in measurement, imaging and spectroscopy. There also are some other aspects of collaboration and partnership with Leeds that have grown up over the last 30 years and we will discuss these in the context of good models for university/industrial relationships. Agilent Measurement Journal 53

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 4 - 2008

Agilent Measurement Journal - Issue 4 - 2008 Delivering Confidence through Compliance with Standards Contents Emerging Innovations Trying Early Device Implementations at the IEEE 1588 PlugFest Achieving Greater Confidence in Measurement Accuracy through Consistency in Calibration Services Overcoming the Challenges of RFID Component Testing 3GPP LTE: Introducing Single- Carrier FDMA Ensuring Reliable Operation and Performance in Converged IP Networks Testing Storage Area Networks and Devices at 8.5-Gb/s Fibre Channel Rates Choosing an Appropriate Calibration Method for Vector Network Analysis Making Traceable EVM Measurements with Digital Oscilloscopes Exploring Terahertz Measurement, Imaging and Spectroscopy: The Electromagnetic Spectrum’s Final Frontier Interpreting Quoted Specifications when Selecting Digitizers

Agilent Measurement Journal - Issue 4 - 2008

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