Abstract
A review is provided of sources and detectors that can be employed in the THz range before the description of an opto-electronic source of monochromatic THz radiation. The realized spectrometer has been applied to gas phase spectroscopy. Air-broadening coefficients of HCN are determined and the insensitivity of this technique to aerosols is demonstrated by the analysis of cigarette smoke. A multiple pass sample cell has been used to obtain a sensitivity improvement allowing transitions of the volatile organic compounds to be observed. A solution to the frequency metrology is presented and promises to yield accurate molecular line center measurements.
Highlights
The Terahertz (THz) frequency domain is often referred to as the range from 100 GHz to 10 THz and is variously known as the sub-mm or far-infrared region, generally depending on the techniques employed for the generation of the radiation
THz absorption profiles of volatile polar molecules, in particular over the frequency interval 1 THz to 3 THz where few alternatives can rival its performance. The potential of this instrument has been extended by increasing its sensitivity and adding a mechanism by which the THz frequency is accurately synthesized
The ability to measure weakly absorbing transitions has allowed a number of gas phase species to be quantified in a sample of unfiltered cigarette smoke, demonstrating the utility of THz radiation to probe normally diffuse media
Summary
The Terahertz (THz) frequency domain is often referred to as the range from 100 GHz to 10 THz and is variously known as the sub-mm or far-infrared region, generally depending on the techniques employed for the generation of the radiation. Compared to other frequency regimes the THz region has suffered from a significant lack of technological development and so this part of the electromagnetic spectrum is only presently being explored and applications identified. The most well known THz application that has been identified is the security screening of airline passengers, the astrophysics community has quietly and successfully utilized THz radiation for a number of decades during which it has provided significant information such as the visualization of objects hidden behind interstellar dust clouds. The continued development of new and existing applications is dependent on the availability of powerful sources that can cover the entire range, and sensitive detectors with short response times at room temperature
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