Terahertz Technology

Terahertz waves are electromagnetic waves in the frequency range between 100 GHz and 10 THz and are thus classified between the infrared and microwave range. The associated wavelengths range from 3 mm to 30 μm.

Terahertz waves combine the advantages of the two adjacent spectral ranges: High penetration depth and low scattering combined with good spatial resolution are characteristic of terahertz waves. Unlike UV or X-rays, for example, terahertz waves do not alter the chemical structure of substances and materials under investigation. Moreover, since the power levels used in the applications addressed here are very low, the use of this technology is therefore harmless to humans.

Most materials are transparent to terahertz waves.

There are basic limitations with:

  • Metals and other electrically conductive materials reflect the terahertz waves. This means that the interior cannot be examined, only the surface and the coating of this can be tested.
  • Polar liquids like water absorb terahertz waves very well. On the one hand, this greatly limits the penetration depth of terahertz waves into materials containing water, such as skin or biological tissue. On the other hand, however, the water content in materials can be detected very sensitively.

There is no fixed threshold of electrical conductivity or water content below which investigation with terahertz waves is possible. The material thickness must also be taken into account here.

There Is Not Only One Terahertz Technology

The terahertz spectral range has now been technically developed. Users can choose from a wide range of components and sensors for this frequency range. There is no longer the terahertz gap that was often cited in the past. Users can choose from a wide range of components and sensors for this frequency range.

Since the spectral range has been developed from the two adjacent ranges, there is not THE terahertz technology. Rather, many technological approaches are being taken to tap it. In industrial use can be found:

  • Terahertz TDS system (Time Domain Spectroscopy). This technique, based on short-pulse lasers, enables very precise time-of-flight measurements or spectroscopic investigations due to the short pulses or the broad spectrum.
  • FMCW radars (Frequency Modulated Continuous Wave). Due to the use of waveguides or integration on a chip, these fully electronic radars have a lower fire energy and thus a lower depth resolution than TDS systems. Due to their special design, they are generally smaller and less expensive than TDS systems and have a higher measurement rate.

Other techniques such as CCS (Cross-Correlation Spectroscopy) and optical FMCW are currently being tested and will reach industrial maturity in the next few years. 

We deal with all these techniques and therefore select the most suitable method for the respective application in an open-minded way.


Terahertz Spectroscopy

One of the established measurement techniques in the terahertz spectral range is terahertz time domain spectroscopy (TDS). It is based on the generation of broadband electromagnetic radiation by ultra-short femtosecond (fs) laser pulses and on detection with the pump-probe principle.

Terahertz Imaging

By means of terahertz imaging – similar to X-rays and ultrasound - images of the interior of the object can be generated. In this way, manufacturing-related defects or weak points in the object can be detected during production. Terahertz technology thus makes an important contribution to industrial quality control and conserves resources.