In this paper we present the outcome of the first international comparison in the terahertz frequency range among three different kinds of spectrometers. A Fourier-Transform infrared spectrometer, a Vector Network Analyzer and a Time-Domain Spectrometer have been employed for measuring the complex refractive index of three travelling standards made of selected dielectric materials in order to offer a wide enough range of parameters to be measured. The three spectrometers have been compared in terms of measurement capability and uncertainty.
Terahertz time-domain spectroscopy (THz TDS) is a well-known tool for material\ud
analysis in the terahertz frequency band. One crucial system component in every time-domain\ud
spectrometer is the delay line which is necessary to accomplish the sampling of the electric\ud
field over time. Despite the fact that most of the uncertainty sources in TDS have been\ud
discussed, the delay line uncertainty has not been considered in detail. We model the impact\ud
of delay line uncertainty on the acquired THz TDS data. Interferometric measurements of the\ud
delay line precision and THz time-domain data are used to validate the theoretical model
We report on an optical frequency standard at λ 612 nm, which takes the form of a He-Ne laser stabilized with respect to molecular iodine by means of frequency modulation spectroscopy. The measured frequency stability was 8,7 10 -13 for sampling times between 10 -3 s and 10 3 s, and the estimated reproducibility was 1,2 kHz. Spectroscopy of the R(47) 9-2 transition was performed, and iodine hyperfine constants were calculated.
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