Gert Rabe

Phase matching in symmetrical single‐mode magneto‐optic waveguides by application of stress

Tuning of the propagation constant difference Δβ=βTM−βTE in single‐mode symmetrical yttrium iron garnet (YIG) film waveguides over a range of 250°/cm by means of external stress is demonstrated. An a posteriori, precise setting of phase match Δβ→0, which is a precondition for nonreciprocal mode coupling type components, can be achieved by this method.

45° waveguide isolators with phase mismatch

45° waveguide isolators based on magneto‐optic channel waveguides with phase mismatch can be realized simply by choosing a proper orientation of the input polarization. This is demonstrated theoretically by visualizing the magneto‐optic mode coupling as ‘‘coupling tracks’’ on the Poincare sphere, and is verified experimentally for real waveguides with considerable phase mismatch. More than 30 dB isolation is feasible in practical devices.

Influence of the barrier preparation on the quality of NbN/MgO/NbN Josephson junctions

NbN/MgO/NbN Josephson tunnel junctions have been prepared using various barrier preparation conditions. The energy of the sputtered MgO particles arriving at the substrate was found to be the most important parameter. Tunnel junctions (10*10 mu m2) with Vm values of up to 23 mV have been fabricated. The optimized NbN/MgO/NbN junction process is extended to a reliable whole-wafer process for DC SQUID fabrication.