Checking people at airports with terahertz radiation
PTB succeeds in absolute measurement of terahertz radiation
Radiation in the THz range penetrates clothing and many other organic materials and furthermore offers spectroscopic information on safety-relevant materials such as explosives and pharmacological substances. The broad spectrum of the possible applications extends from security check to the investigation of the spatial and/or time structure of the electron packages in the storage rings for synchrotron radiation production and in free-electron lasers, for which the receivers of the German Electron Synchrotron DESY characterized here are used.
The complete information on the THz spectra can only be determined with detectors of known spectral responsivity. Up to now, the integral responsivity of the respective detectors and their spectral distribution are still largely unknown. The PTB has now for the first time determined the spectral responsivities of two THz detectors in the wavelength range from 50 µm to 600 µm with the aid of cavity radiators.
In order to make available spectral radiation fluxes in the THz range, calculable according to Planck's radiation law, the PTB uses two THz cavity radiators at different temperatures in connection with THz band and longwave-pass filters. The interior surfaces of the radiators are provided with a special coating which possesses a known and high emissivity also in the THz range and thus enables the calculability of the radiation incident on the detector. In order to obtain a sufficiently spectral purity of the THz radiation, a suppression of the infrared radiation of more than nine orders of magnitude is necessary.
By using an FT-IR spectrometer, the transmittance for all filter combinations used was accurately determined in the wavelength range from 0.8 µm to 1700 µm. Due to the calculable radiation of the cavity radiators and the known transmittance of the filters, it is possible to accurately determine the spectral radiation fluxes and thus determine the spectral absolute responsivities of THz receivers for the first time. Such absolutely characterized receivers will in future be utilized, e.g., both at the Metrology Light Source of the PTB to investigate the THz radiation produced there and in the investigation of the effect of THz radiation on the biological cell cycle.
Other news from the department science
These products might interest you
Most read news
More news from our other portals
See the theme worlds for related content
Topic World Spectroscopy
Investigation with spectroscopy gives us unique insights into the composition and structure of materials. From UV-Vis spectroscopy to infrared and Raman spectroscopy to fluorescence and atomic absorption spectroscopy, spectroscopy offers us a wide range of analytical techniques to precisely characterize substances. Immerse yourself in the fascinating world of spectroscopy!
Topic World Spectroscopy
Investigation with spectroscopy gives us unique insights into the composition and structure of materials. From UV-Vis spectroscopy to infrared and Raman spectroscopy to fluorescence and atomic absorption spectroscopy, spectroscopy offers us a wide range of analytical techniques to precisely characterize substances. Immerse yourself in the fascinating world of spectroscopy!