Jan Ornik, Jannik Lehr, Marco Reuter, David Jahn, Felipe Beltran-Mejia, Jan C. Balzer, Thomas Kleine-Ostmann, and Martin Koch
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| Experimental setup composed of a pair of photoconductive antennas, a delay line and a femtosecond fiber laser emitting at 780 nm. The laser beam forms the optical path as depicted by the red lines. The blue region represents the THz radiation that impinges one of the five cuvettes. |
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-28-19-28178
Recently, many research groups worldwide have reported on the THz properties of liquids. Often these parameters, i.e., refractive index and absorption coefficient, are determined using liquids in cuvettes and terahertz time-domain spectroscopy. Here, we discuss the measurement process and determine how repeatable such measurements and the data extraction are using rapeseed oil as a sample. We address system stability, cuvette positioning, cuvette cleaning and cuvette assembly as sources affecting the repeatability. The results show that system stability and cuvette assembly are the most prominent factors limiting the repeatability of the THz measurements. These findings suggest that a single cuvette with precise positioning and thorough cleaning of the cuvette delivers the best discrimination among different liquid samples. Furthermore, when using a single cuvette and measurement systems of similar stability, the repeatability calculated based on several consecutive measurements is a good estimate to tell whether samples can be discriminated.
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