We search for novel THz sources, investigate THz light-matter interaction and novel two-dimensional photonic devices.

Research towards materials and devices determined by dimensions and structural control in the nanometer range is a large effort with many resources dedicated worldwide. This interest is driven, on one hand, by basic science, because quantum phenomena determine the properties and pave the road towards new functions. On the other hand, rapid development of industrial technology demands materials and devices with more functionality, higher switching speeds, and higher integration. These requirements led to the development of fabrication techniques on the atomic scale which open the way towards the realization of revolutionary concepts in solid state science and technology.

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Research topics

Quantum cascade lasers (QCLs) are novel semiconductor devices. Unlike ordinary band gap lasers known from everyday life (laser pointers, Blu-ray/DVD/CD drives), they are using a radically new concept. The energy levels in a quantum cascade laser are formed by quantum mechanically bound states in an artificially grown semiconductor nanostructure. Therefore they are also known as intersubband lasers.

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Terahertz time domain spectroscopy is a powerful spectroscopic technique that allows the time-resolved measurement of light-matter interaction with broadband and powerful THz pulses. Contrary to other spectroscopies, amplitude and phase information are directly retrieved in a single scan, making THz TDS a powerful tool for studying absorption and gain dynamics in semiconductor heterostructures. The time information allows further to retrieve depth information as is used in time-of-flight tomographic imaging.

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The terahertz and mid-infrared spectral region is most suited for the study of novel optical materials and phenomena. We study, for example, THz polaritonics with metamaterials and quantized transitions in semiconductors, light-matter interaction of optical nano-antennas and semiconductor quantum dots and novel two-dimensional materials like graphene or MoS2

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