| Description |
For many decades the terahertz frequency range (0.1–10 THz) in the spectrum of electromagnetic radiation had found little attention as it is difficult to access. From the point of view of optics it was below the range of frequencies (or photon energies of 0.4 to 40 meV) accessible by conventional optical methods. On the other hand, it was hardly possible to reach this frequency range with RF methods. Therefore, there was the “THz gap”, separating the optical from the RF range of the electromagnetic spectrum. With the progress in both optoelectronics and RF electronics this gap could be narrowed from both sides, or even be closed, during the past decade. This development was powered by an increased interest in many possible applications for this radiation ranging from imaging and spectroscopy allowing for the identification of biological and chemical hazardous materials or explosives, to environmental monitoring on earth or heterodyne detection of cosmic background radiation. This talk will be focused on continuous wave (CW) THz radiation. Our approach used for generation is photo-mixing (or optical heterodyning). It combines optical methods (two laser beams with a difference in frequency corresponding to the THz frequency, generating a THz electron current in a semiconductor) with RF technology (an antenna for the emission of the radiation). I will discuss the physics aspects of the THz generation as well as our recent applications of the CW-THz radiation for coherent ultra-long wavelength optics.
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