Ronald Ulbricht

Learn More
We propose and theoretically demonstrate a novel type of optical Yagi-Uda nanoantennas tunable via variation of the free-carrier density of a semiconductor disk placed in a gap of a metallic dipole feeding element. Unlike its narrowband all-metal counterparts, this nanoantenna exhibits a broadband unidirectional emission and demonstrates a bistable response(More)
We present a comparative study of the ultrafast photoconductivity in two different forms of one-dimensional (1D) quantum-confined graphene nanostructures: structurally well-defined semiconducting graphene nanoribbons (GNRs) fabricated by a "bottom-up" chemical synthesis approach and semiconducting carbon nanotubes (CNTs) with a similar bandgap energy.(More)
Single-photon emission from the nitrogen-vacancy defect in diamond constitutes one of its many proposed applications. Owing to its doubly degenerate 3E electronic excited state, photons from this defect can be emitted by two optical transitions with perpendicular polarization. Previous measurements have indicated that orbital-selective photoexcitation does(More)
/TiO 2 exhibit oscillations similar to that for p-GaInP 2 /Pt, meaning that the surface field increases substantially when the TiO 2 thickness increases from 0.5 to 35 nm. The formation and decay time constant of DF for these samples are extracted from the corresponding TPR kinetics (fig. S9B). Best-fit parameters are tabulated in table S1. Thicker TiO 2(More)
"Selective detection of bacterial layers with terahertz plasmonic antennas" multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. Abstract: Current detection and identification of microorganisms is based on either rather unspecific rapid microscopy or on more accurate(More)
  • 1