Erzeugung von Terahertzstrahlung durch nichtlinear-optische Mischprozesse von kohärenter Mittelinfrarotstrahlung in Halbleiter-Wellenleiterstrukturen

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The aim of the present proposal is the direct generation of coherent continuous wave (CW) THz radiation by a nonlinear optical (NLO) approach via difference frequency generation (DFG) in III-V compound semiconductor waveguides due to the second order nonlinear optical susceptibility χ(2) of GaAs or InGaAs, i.e., the intra-waveguide interaction of a pump frequency ωP and a signal frequency ωS resulting in an idler frequency ωi = ωP - ωS in the THz range. Here, the second order non-linearity of GaAs or InGaAs will be explored in the mid-infrared (MIR) at ~ 5-20μm by powerful quantum cascade lasers as the laser source. One key requirement of NLO, phase matching, will be realised by form birefringence in optical heterostructures, quasi-phase matching (QPM) and modal polaritonic phase matching (PPM). The working program consists of two experimental key features: a. Realisation of a stable coherent two-wavelength or two-frequency source in the mid-infrared spectral domain (around 5 to 20 μm) with well-controlled tailored spectral performance by external cavity quantum cascade laser configurations. b. Efficient THz generation via nonlinear optical interaction of these two frequencies in semiconductor-based waveguides including a detailed understanding and modelling and optimisation of the nonlinear optical process in strong feedback and interaction with technology partners from the Forschergruppe in Erlangen and Berlin.