Plenarvorträge - DPG-Tagungen

Halbleiterphysik Dienstag
been recently demonstrated in our laboratory. A challenge lies in the massproduction of 50 m 2 wafers with cost-effective methods.
HL 20 Photonische Kristalle IV
Zeit: Dienstag 15:15–17:30 Raum: H17
HL 20.1 Di 15:15 H17
Optical characterisation of opal heterojunctions — •Sergei
Romanov 1 , Dmitry Chigrin 1 , Vladimir Solovyev 1 , Clivia
Sotomayor Torres 1 , Nikolai Gaponik 2 , Alexander Eychmueller
2 , and Andrei Rogach 3 — 1 Inst. of Materials Science
and Dept. of Electrical and Information Engineering, University of
Wuppertal, 42097, Germany — 2 Inst. of Physical Chemistry, University
of Hamburg, 20146, Germany — 3 Dept. of Physics, University of
Munich, 80799, Germany
Interfacing of photonic crystals (PhCs) is a step towards their functionalisation.
The anticipated effects are engineered PBG, light confinement
and directing of the light flow. Hetero-opals were prepared by sandwiching
two thin film opals assembled from latex beads of different diameters,
while staying with preparation by self-assembly. Angle-resolved
reflectance, transmission, scattering and emission of light were used to
characterise hetero-opals.
Anomalous transmission minimum was observed in between two Bragg
gaps of the hetero-opal constituents and associated with the interface.
This observation was supplemented by reflectance and scattering experiments.
Finite difference time domain modelling of light propagation in
2D PhC hetero-junction was used to study this effect.
Anomalies of emission spectra of CdTe nanoparticles embedded in
hetero-opals, which were observed at frequencies of the interface gap,
agree the interface gap model.
HL 20.2 Di 15:30 H17
EFFECTS OF DISORDER IN MICROWAVE REALI-
ZATIONS OF 1D PHOTONIC CRYSTALS: — •G.A.
Luna-Acosta 1,2 , H. Schanze 1 , U. Kuhl 1 und H.-J. Stöckmann 1
— 1 Fachbereich Physik der Philipps Universität Marburg, Renthof 5,
D-35032 — 2 Instituto de Fisica, BUAP, Puebla, Mexico.
We experimentally investigate the effects of structural and impurity
disorder in 1D photonic lattices and superlattices of finite length. These
lattices are realized in the microwave regime by an array of teflon pieces
of length dT alternating periodically with air spacings of length dA in a
single-mode microwave guide experiment. Structural ( positional) disorder
is achieved by an uncorrelated random variation ξ of the air spacings
and/or the teflon inserts. Impurity disorder is realized by placing a few
teflon pieces of length dimp within the air spacing of the ideal crystal. The
manifestation in the transmission measurements of weak, intermediate,
and strong disorder of both types of disorder is analyzed and compared
with simple transfer matrix calculations. We also discuss our results in
connection with theories of correlated and uncorrelated random disorder
in 1D potentials.
HL 20.3 Di 15:45 H17
Resonant 2D-PC structures of moderate refractive index
materials — •Gunnar Böttger, Markus Schmidt, Karolin
Preusser-Mellert, Alexander Petrov, and Manfred Eich —
Technische Universität Hamburg-Harburg, AB 4-09, 21071 Hamburg
We present simulations and experimental measurements of transmission
properties of photonic crystal slab structures defined by air holes
etched into polymeric slab waveguides. Geometric defects in otherwise
regular photonic crystal slab structures strongly localize optical fields,
forming resonators of significant quality factors that may e.g. be used
in novel filtering devices for optical telecommunications (1330 and 1550
nm). We show what influence parameters like etching depth and vertical
contrast have on attainable quality factors and on transmission as well
as coupling efficiencies. First results are presented on the use of ultra low
index substrates.
HL 20.4 Di 16:00 H17
Emitting quantum dots under photonic confinement: composite
materials design and fabrication — •Nikolai Gaponik 1 , Richard
Capek 1 , Alexander Eychmüller 1 , Andrey Rogach 2 , Clivia Sotomayor
Torres 3 , and Sergei Romanov 3 — 1 Institute of Physical
Chemistry, University of Hamburg, 20146 Hamburg — 2 Photonics and
Optoelectronics Group, Department of Physics and CeNS, University
of Munich, 80799 Munich — 3 Institute of Materials Science and Department
of Electrical and Information Engineering, University of Wuppertal,
42097 Wuppertal
Strongly luminescent colloidal quantum dots (QDs) were integrated
into various types of opal-based photonic structures and microcavities.
The post-preparative treatment of QD surface was demonstrated to be a
powerful tool to give precise control over the luminescent photonic composite
materials properties. Both the layer-by-layer assembly and solventcontrolled
precipitation techniques were optimized to be used for formation
and selective modification of light-emitting hetero-opals. Structural
and optical properties of fabricated composite materials are reported.
HL 20.5 Di 16:15 H17
Cavity QED phenomena in Photonic Crystal Microcavities containing
self-assembled Quantum Dots — •A. F. Kreß, F. Hofbauer,
H. J. Krenner, D. Schuh, R. Meyer, and J. J. Finley —
Walter Schottky Institut, TU München, 85748 Garching, Germany
We present optical investigations of active photonic crystal defect mircocavities
(PCµC) formed from a hexagonal lattice of air-holes in a GaAs-
(Al)GaAs slab waveguide. Incorporation of one or more layers of self assembled
InGaAs quantum dots (QD) into the waveguide enable us to
directly probe the nature of the cavity modes using spatially resolved
photoluminescence (µPL) spectroscopy. Moreover, cavity-QED phenomena
have been directly observed using time resolved spectroscopy.
The fully localised PCµC modes show strongly enhanced light emission
with Q>500 for a modevolume of ∼ 3(λ/n) 3 . Time resolved measurements
clearly demonstrate Purcell enhancement of the spontaneous
emission rate with Purcell factors up to ∼4 having been observed.
Control of the design and symmetry of the PCµC allows us to engineer
the cavity modes. µPL measurements on a series of H2 PCµCs
demonstrate our ability to tune the wavelength of the cavity modes over
∼ ±30nm around ∼950nm with a precision better than ∼1nm. Tuneable
cavity states are investigated in different hexagonal crystals and exhibit
mode structure in good accordance with our calculations. Improved
PCµC designs for reduced symmetry ultra high Q-cavities will also be
presented. Finally, we will discuss a device concept for an electronically
tuneable PCµC for planned single QD cavity QED experiments.
HL 20.6 Di 16:30 H17
Metal-Dielectric Photonic Crystals from Gold Coated opals
— •Andrei Susha 1 , Paul Miclea 2 , Clivia Sotomayor Torres 2 ,
Sergei Romanov 2 , and Frank Caruso 3 — 1 Dept. of Physics, University
of Munich, 80799, Germany — 2 Inst. of Materials Science, Dept. of
Electrical and Information Engineering, University of Wuppertal, 42097,
Germany — 3 Dept. of Chemical and Biomolecular Engineering, University
of Melbourne, Victoria 3010, Australia
The promise of metal-dielectric (MD) opals is to be photonic crystals
(PhC) with wide and robust photonic bandgap (PBG). To prepare
films of MD opals, the latex spheres were coated by 5nm Au nanoparticles
(NP). The angular-resolved reflectance spectroscopy in the visible
and near-infrared ranges, the surface diffraction and light scattering were
used to study their PBG.
The surface plasmon resonance of Au NPs changes in opals from the
single peak to the set of peaks in correspondence to the shape of NCs
aggregates. The diffraction resonance in Au-opals evolves away from the
dielectric-type behaviour, when it overlaps the plasmon resonance. Increase
of the Au content up to 50 wt. emerging bands with unusual
angular dispersion. Experimental data are discussed in the light of theory
predictions.