Coupling and Cavity Interaction in Quantum Cascade Lasers and Detectors - Project 09

Project Leader: Gottfried Strasser

This project part of of Next-Lite uses novel intersubband device concepts by combining epitaxial growth and processing of III-V materials to realize new cavity designs, coupling between cavities, and strong cavity–intersubband interaction. Coupling between cavities via evanescent field or direct coupling will be investigated, fabricating various coupling scenarios of active materials in these cavities in the MIR and, together with Unterrainer (P02), at THz frequencies.

The growth of novel material combinations will not only used to increase the performance of the proposed devices, but also to study the influence of interfaces, alloy scattering, and doping profiles on light matter interactions. Shaping of beam profiles in QCLs will be done utilizing surface plasmons [Yu08], photonic crystals [Xu09, Chassagneux09], and ring DFBs [Mujagic10]. On a longer time scale we want to be able to change or completely switch the coupling strength between cavities. With Rotter (P10) sophisticated cavity designs will be proposed and fabricated. Intersubband detectors using QWIPs or quantum cascade designs will be combined with photonic crystals to circumvent polarization constrictions [Kalchmair11].

Short-term goals are optimization of detector performance by integrating PhCs, QWIPs, and free standing slabs, long-term goals are novel resonator structures for active source materials,the combination of mechanical and optical cavities, and quantum structures allowing emission and detection at the same wavelength to get more insight into light matter interactions. Polaritons can probe strong light-matter coupling in THz micro-cavities and nanostructures [Todorov10]. This strong coupling utilizing intersubband transitions with polaritons is an alternative approach to the work we plan with Unterrainer (P02), using a timedomain THz method.

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