Terahertz (THz) radiation is an established tool for diagnostics in addition to instrumentation and test engineering. On March 2nd, the Fraunhofer Institute for Physical Measurement Techniques IPM opened the new TeraTec application center for terahertz technology in Kaiserslautern. There, the Fraunhofer experts will be making a wide range of differing terahertz systems available to companies for testing or as services.
THz radiation is electromagnetic radiation and covers a frequency range of 0.1 to 10 THz. Many molecules show characteristic absorption spectra in this spectral range. The penetration of THz radiation is comparatively high: many substances which are non-transparent for visible light or infrared (IR) are transparent for THz rays. At the same time, THz radiation is low-energy radiation and non-ionizing. The specific interaction of THz radiation with different substances opens up new perspectives for a large number of applications in measurement technology.
Much progress has been made in laser and semiconductor technologies since the early days of THz technology. This has advanced the development of suitable THz emitters and detectors during recent years.
Terahertz Time-Domain-Spectroscopy (THz-TDS) is one of the most established THz based measurement techniques. It is based on the generation of broadband electromagnetic radiation by ultrashort femtosecond laser pulses (fs). The laser beam is split into pump and probe beam. The pump beam is focused on a THz emitter, where THz radiation is generated. The refractive index and the absorption coefficient are derived from the respective spectra of probe and reference. Part of the radiation will be transmitted or reflected and subsequently focused on a detector where it is overlaid with a fs probe beam. Through automatic synchronization with the THz pulses the detection can be performed without cooling and under normal lighting conditions.
Today, THz spectroscopy is a common method in scientific laboratories. Apart from spectroscopy, scanning samples with THz radiation generate two dimensional (imaging) and even three-dimensional images (tomography).
TeraTec combines all the relevant techniques and systems under one roof for contactless inspection and destruction-free material characterization. TeraTec will perform contactless inspection and destruction-free material characterization.
Contactless inspection:
Layer thicknesses
Foreign substances
Moisture
Hidden structures
Delamination
Adhesive bonds
Inhomogeneities
Inspection of packed and non-packed objects
Destruction-free material characterization:
Degree of purity
Mixture ratios
Conformation
Polymorphism
Isomers
Differentiation between amorphous and crystalline structures
Charge-carrier mobility and concentration in semiconductors
At the opening, Professor René Beigang, head of the department “Terahertz Measurement and Systems” at Fraunhofer IPM, emphasized the capability for developing tailor-made terahertz solutions to the customer's specifications. Professor Beigang stated “In the application center companies can test whether their specific measurement problems can be solved with the help of terahertz technology.”
The customer's samples will be measured with the terahertz systems available at TeraTec and feasibility studies can be carried out. It is also possible to use mobile terahertz instruments over a certain period of time on a company's own premises.
The Ministry of Education, Science, Youth and Cultural Affairs Rhineland-Palatinate has invested considerable sums in the setting up of the IPM “Terahertz Measurement and Systems” department in Kaiserslautern over the last few years. On top of this, funding was provided in the context of the second economic stimulus package in order to purchase important instruments and to set up industry-capable laboratory equipment. Fraunhofer IPM's director Elmar Wagner pointed out that the working group “is now leading the field in the implementation of terahertz instrumentation engineering for industry in Germany.”
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