Luftuntersuchung

Ohne Zusammenfassung     

Germanium based photonic components toward a full silicon/germanium photonic platform

Lately, germanium based materials attract a lot of interest as they can overcome some limits inherent to standard Silicon Photonics devices and can be used notably in Mid-Infra-Red sensing applications. The quality of epitaxially grown intrinsic and doped materials is critical to reach the targeted performances. One of the main challenges in the field remains the fabrication of efficient group-IV laser sources compatible with the microelectronics industry, seen as an alternative to the complexity of integration of III-V lasers on Si. The difficulties come from the fact that the group-IV semiconductor bandgap has to be transformed from indirect to direct, using high tensile strains or by alloying germanium with tin. Here, we review recent progresses on critical germanium-based photonic components such as waveguides, photodiodes and modulators and discuss the latest advances towards germanium-based lasers. We show that novel optical germanium-On-Insulator (GeOI) substrates fabricated by the Smart Cut? technology is a key feature for future Si - Complementary Metal Oxide Semiconductor (CMOS) - compatible laser demonstration. This review hints at a future photonics platform based on germanium and Silicon.     

Phase-amplitude characterization of a high-repetition-rate quantum dash passively mode-locked laser

We apply a novel phase-amplitude characterization method to a one-section quantum dash-based passively mode-locked laser at a 42.2 GHz repetition rate. The method relies on the measurement of the spectral phase of the longitudinal modes by the successive analysis of the correlation signal of a group of three adjacent modes. It provides both the temporal shape of the intensity and the phase of the emitted signal. A pulse of 1.5 ps of width is measured, and a pedestal is exhibited. Extinction ratio limitation is explained by investigating the origin of this pedestal. The accuracy of the method is estimated by comparing the measured autocorrelation signal and the calculated one from the phase analysis.     

Shubnikov de haas oscillations in Cd3-xZnxAs2 alloys

These first measurements of the Shubnikov de Haas effect in Cd_3-xZn_xAs₂ alloys were performed with x values ≤0.6. The electron effective mass is shown to be anisotropic but much less than Cd₃As₂ samples of similar Fermi energies. Spin splitting was observed yielding g values of up to 43 for the purest sample.     

Fundamental symmetries studies with cold trapped francium atoms at ISAC

Francium combines a heavy nucleus (Z = 87) with the simple atomic structure of alkalis and is a very promising candidate for precision tests of fundamental symmetries such as atomic parity non-conservation measurements. Fr has no stable isotopes, and the ISAC radioactive beam facility at TRIUMF, equipped with an actinide target, promises to provide record quantities of Fr atoms, up to 10¹⁰/s for some isotopes. We discuss our plans for a Fr on-line laser trapping facility at ISAC and experiments with samples of cold Fr atoms. We outline our plans for a measurement of the nuclear anapole moment – a parity non-conserving, time-reversal conserving moment that arises from weak interactions between nucleons – in a chain of Fr isotopes. Its measurement is a unique probe for neutral weak interactions inside the nucleus.