Online THz system

For many applications it is required to measure the THz signal in real time. In order to do this we have exchanged the "slow" delay line by a fast scanning device (shaker) which is able to scan a range of 45 mm with a repetition rate of up to 10 Hz. A p-InAs surface emitter with high average output power was used to measure the THz signal directly without any lock-in techniques. In this way realtime THz signals with 20 samples per second were measured in the time domain. 

A typical example is shown in the movie below. An oscilloscope displays the THz signal versus scanning position. The time shift of the THz peak as a function of sample position and the peak maximum of the electrical field can be detected directly. In this way material thickness (or density), holes within solid items or hidden Objects can be measured e.g. in production, final inspection or customs check.

Terahertz (THz), online THz system, non-destructive testing, tomography, thickness measurements, industrial applications

[1] "Terahertz-Wellen – ein neuer Spektralbereich für die industrielle Messtechnik (Terahertz Waves – A New Spectral Band for Industrial Measurement Techniques)“, F. Ellrich, T. Weinland, J. Klier, J. Jonuscheit, and R. Beigang, tm-Technisches Messen, Vol. 77, No. 9, pp. 452-461 (2010)
 summary copyright

[2] "Fasergekoppeltes Terahertz-Spektroskopiesystem (Fiber-coupled Terahertz Spectroscopy System)", F. Ellrich, T. Weinland, M. Theuer, J. Jonuscheit, and R. Beigang, tm-Technisches Messen, Vol. 75, No. 1, p. 14-22 (2008)
 summary copyright

[3] "Einsatz breitbandiger THz-Strahlung in der Gasanalyse (Broadband THz-Radiation for Gas Analysis)", C. Weiss, E. Viehl, Ch. Theiss, G. Torosyan, M. Weinacht, R. Beigang and R. Wallenstein, tm-Technisches Messen, Vol. 68, No. 9, p. 388 (2001)
 summary copyright

[4] "Terahertz-Bildgebung in industriellen Anwendungen (Terahertz Imaging in Industrial Applications)", M. Theuer, G. Torosyan, F. Ellrich, J. Jonuscheit, and R. Beigang, tm-Technisches Messen, Vol. 75, No. 1, p. 64-70 (2008)
 summary copyright

[5] "T-ray tomography", D.M. Mittleman, and S. Hunsche, and L. Boivin, and M.C. Nuss, Optics Letters, Vol. 22, No. 12, p. 904-906, (1997)

[6] television contribution:
Christoph Gehring: "Wellen für die Sicherheit", SWR>>RP aktuell vom 05. März 2008, Beitrag: "Wellen für die Sicherheit" (6,1 MB), Copyright: SWR.de