Interaction of Femtosecond Lasers with Semiconductors (English shop)

Terahertz Frequency Combs and Terahertz Steering

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The terahertz (THz) frequency range has gained considerable importance for science and industry in recent years. In this part of the electromagnetic spectrum, long regarded as inaccessible from an application perspective, a wide variety of spectroscopic and imaging techniques have since become established. Applications in security technology and the telecommunications sector now also operate at frequencies in the high gigahertz to low THz range.

This dissertation addresses two aspects that are of central importance for these novel technologies: the detection and the generation of THz radiation. Optoelectronic techniques are employed, based on the excitation of semiconductor materials by femtosecond lasers. By means of the so-called THz frequency comb, continuous-wave THz sources can thus be characterised with the highest measurement accuracy and spatially resolved emission profiles of the sources can be produced. This is investigated using two detection methods, electro-optic and photoconductive detection. THz generation is realised through the excitation of short currents in the semiconductor material. Here, the emission direction of the THz fields can be controlled solely via the properties of the excitation light, allowing the first purely optically controlled THz source to be demonstrated.