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Highly sensitive terahertz measurement of layer thickness using a two-cylinder waveguide sensor

: Theuer, M.; Beigang, R.; Grischkowsky, D.


Applied Physics Letters 97 (2010), Nr.7, Art. 071106, 3 S.
ISSN: 0003-6951
ISSN: 1077-3118
Fraunhofer IPM ()

We report on the layer thickness determination on dielectrically coated metal cylinders using terahertz (THz) time-domain spectroscopy. A considerable sensitivity increase of up to a factor of 150 is obtained for layers down to 2.5 µm thickness by introducing an experimental geometry based on a two-cylinder waveguide sensor. The layer attached on one metal cylinder is guided in contact with the second metal cylinder in the THz beam waist. This approach uses concepts of adiabatic THz wave compression and the advantages of THz waveguides. The results are compared to measurements on free-standing layers.