arXiv subjects

Gregor Koblmüller

Publications and source records attributed to Gregor Koblmüller.

21 records · Page 2Linked to original sources

arXiv2012

Surface acoustic wave controlled charge dynamics in a thin InGaAs quantum well

We experimentally study the optical emission of a thin quantum well and its dynamic modulation by a surface acoustic wave (SAW). We observe a characteristic transition of the modulation from one maximum to two maxima per SAW cycle as the acoustic power is increased which we find in good agreement with numer- ical calculations of the SAW controlled carrier dynamics. At low acoustic powers the carrier mobilites limit electron-hole pair dissociation, whereas at high power levels the induced electric fields give rise to efficient acousto-electric carrier transport. The direct comparison between the experimental data and the numerical simulations provide an absolute calibration of the local SAW phase.

cond-mat.mes-hall↗

arXiv2012

Coupling of guided Surface Plasmon Polaritons to proximal self-assembled InGaAs Quantum Dots

We present investigations of the propagation length of guided surface plasmon polaritons along Au waveguides on GaAs and their coupling to near surface InGaAs self-assembled quantum dots. Our results reveal surface plasmon propagation lengths ranging from 13.4 {\pm} 1.7 μm to 27.5 {\pm} 1.5 μm as the width of the waveguide increases from 2-5 μm. Experiments performed on active structures containing near surface quantum dots clearly show that the propagating plasmon mode excites the dot, providing a new method to spatially image the surface plasmon mode. We use low temperature confocal microscopy with polarization control in the excitation and detection channel. After excitation, plasmons propagate along the waveguide and are scattered into the far field at the end. By comparing length and width evolution of the waveguide losses we determine the plasmon propagation length to be 27.5 {\pm} 1.5 μm at 830 nm (for a width of 5 μm), reducing to 13.4 {\pm} 1.7 μm for a width of 2 μm. For active structures containing low density InGaAs quantum dots at a precisely controlled distance 7-120 nm from the Au-GaAs interface, we probed the mutual coupling between the quantum dot and plasmon mode. These investigations reveal a unidirectional energy transfer from the propagating surface plasmon to the quantum dot. The exquisite control of the position and shape afforded by lithography combined with near surface QDs promises efficient on-chip generation and guiding of single plasmons for future applications in nanoscale quantum optics operating below the diffraction limit.

physics.optics↗

arXiv2010

In vacancies in InN grown by plasma-assisted molecular beam epitaxy

The authors have applied positron annihilation spectroscopy to study the effect of different growth conditions on vacancy formation in In- and N-polar InN grown by plasma-assisted molecular beam epitaxy. The results suggest that the structural quality of the material and limited diffusion of surface adatoms during growth dictate the In vacancy formation in low electron-density undoped epitaxial InN, while growth conditions and thermodynamics have a less important role, contrary to what is observed in, e.g., GaN. Further, the results imply that in high quality InN, the electron mobility is likely limited not by ionized point defect scattering, but rather by threading dislocations.

cond-mat.mtrl-sci↗