“Phase-resolved THz spectroscopy.”

  • Date: Jul 12, 2012
  • Time: 11:30 AM - 11:30 AM (Local Time Germany)
  • Speaker: Prof. Dr. Karl Unterrainer, TU Wien, Photonik Institut u. Zentrum für Mikro- & Nanostrukturen
  • Room: Herbert Walther Lecture Hall
  • Host: MPQ
"The generation of coherent THz pulses from femto-second sources has enormously progressed during the last 10 years. The band-width, intensities, as well as the efficiency has increased by using advanced semiconductor emitters and non-linear processes. In this way the spectral range up to 100 THz can be covered by quasi single cycle THz pulses. This frequency range – previously inaccessible for time-resolved spectroscopy - is an important part of the electro-magnetic spectrum due to a large number of fundamental resonances. Vibrational and rotational resonances of molecules are attractive for chemical sensing (chemical fingerprint analysis) and spectroscopic imaging. In solids, the resonance energies of phonons, plasmons and impurity transition are within the THz range. In particular also the transition energies of semiconductor nano structures occur in the THz band.Time-resolved THz spectroscopy allows phase-locked measurements – in particular phase-resolved detection. We take advantage of this fine capability to study the dynamics of semiconductor nanostructures. Phase-resolved THz spectroscopy allows unique measurements of stimulated emission form Quantum-Cascade Lasers. The knowledge of the phase of the THz response provides fascinating insights into the quantum mechanical processes. The study of highly excited nanostructures allows the prediction for coherent control schemes for optoelectronic devices. Together with novel resonator concepts we are able to show THz “switching” and strong coupling to quantized transitions."
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