Plenarvorträge - DPG-Tagungen

Halbleiterphysik Montag
HL 12.28 Mo 16:30 Poster A
Tuning a 2-D silicon photonic crystal using nonlinear optics —
•Stefan L. Schweizer 1 , Hong W. Tan 2 , Henry M. van Driel 2 ,
Ralf B. Wehrspohn 1 , and Ulrich Gösele 3 — 1 Universität Paderborn,
Dept. Physik, 33095 Paderborn — 2 Department of Physics, University
of Toronto, Canada — 3 MPI für Mikrostrukturphysik, Weinberg
2, 06120 Halle
Photonic crystals (PC) have unusual dispersion properties that can be
used to control the propagation characteristics of light beams. However,
for some potential active devices, one desires methods to tune these optical
properties quickly. We use pump-probe reflectivity experiments with
130 fs pulses to demonstrate how the real (Kerr) and imaginary (two
photon absorption) parts of a third order optical nonlinearity can tune
the long (1.6 µm) and short wavelength (1.3 µm) band-edges of a stop
gap in a 2-D silicon photonic crystal. A 2 µm pump pulse induces optical
tuning of the 1.3 µm edge via the Kerr effect whereas a 1.76 µm
pump pulse induces tuning of the 1.6 µm band edge via both Kerr and
Drude effects with the latter related to 2-photon induced generation of
free carriers with a lifetime of ≈900ps.
HL 12.29 Mo 16:30 Poster A
Trimming of two dimensional photonic crystal structures —
•Markus Schmidt 1 , Gunnar Boettger 1 , Karolin Preusser-
Mellert 1 , Manfred Eich 1 , Uwe Huebner 2 , and Hans-Georg
Meyer 2 — 1 Technische Universitaet Hamburg-Harburg, AB 4-09, Eissendorfer
Str. 38, D-21073 Hamburg — 2 Institut fuer Physikalische
Hochtechnologie Jena e. V., Abt. Kryoelektronik, Winzerlaer Str. 10 D-
07745 Jena
We present a new concept to adjust the transmission properties of a
two dimensional photonic crystal based on photobleaching. A square lattice
of 500 nm lattice constant and 300 nm hole diameter was fabricated
by etching air holes into a slab waveguide consisting of a polymethylmethacrylate
polymer covalently functionalized with 10 mol % of the
Disperse Red 1 chromophore. While illuminating the photonic crystal
with UV light the azo molecule bonds degenerate, resulting in a considerable
refractive index change and a slightly reduced slab waveguide core
layer thickness. Wavelength and polarization dependent measurements
show that the dielectric band edge can be shifted strongly, achieving maximum
shifts of 35 nm in TE and 27 nm in TM polarization. Bleaching
of a finite 2d-resonator results in a 22 nm higher resonance wavelength.
In practical applications much smaller shifts are needed to tune Dense
Wavelength Division Multiplexing (DWDM) - devices. Our novel concept
therefore allows to compensate fabrication inaccuracies and to trim
photonic crystal transmission properties.
HL 12.30 Mo 16:30 Poster A
Reflection from two- and three-dimensional Photonic Crystals
— •Marcus Diem 1 , Suresh Pereira 1,2 , and Kurt Busch 1,3 —
1 Institut für Theorie der Kondensierten Materie, Universität Karlsruhe
— 2 Department of Physics, University of Toronto, Canada — 3 School of
Optics/CREOL & Department of Physics, University of Central Florida,
Orlando, USA
We employ a Scattering-Matrix-Method [1] to calculate transmissionand
reflection properties of two- and three-dimensional finite-sized Photonic
Crystal structures. The angle and frequency dependent data can
be directly compared with measurements [2] and allow one to investigate
the quality and parameters of the sample. Peaks in the reflection
spectra associated with different Bragg-orders can be used to determine
the coupling to the modes of the periodic system. This coupling depends
strongly on the surface termination of the Photonic Crystal illustrating
certain complications when interpreting measurements using only the
bandstructures of bulk systems.
In addidtion, we employ this method to determine mode losses in periodically
structured planar waveguides based on optically active polymer
films evaporated onto surface-relief gratings.
[1] D.M. Whittaker and I.S. Culshaw, Phys. Rev. B 60, 2610 (1999)
[2] G. von Freymann et.al, Appl. Phys. Lett 83, 614 (2003)
HL 12.31 Mo 16:30 Poster A
Loss mechanisms in Photonic Crystal slabs — •Meikel Frank 1 ,
Suresh Pereira 1 , and Kurt Busch 2 — 1 Institut für Theorie der Kondensierten
Materie, Universität Karlsruhe, 76128 Karlsruhe, Germany
— 2 School of Optics/CREOL and Department of Physics, University of
Central Florida, Orlando, USA
A scattering matrix method [1] is used to study the optical properties
of Photonic Crystal slabs. Of special interest is the effect of fabricational
tolerances on the propagation characteristics of the modes that are guided
in the ideal system. It is shown that modes in dielectric and air bands,
respectively, exhibit significantly different behavior for certain types of
disorder. For instance, dielectric modes are rather insensitve to errors in
the pore radii, whereas they are strongly affected by variations in the
lattice constant. In addition, it is shown how reflection and transmission
data from finite-sized Photonic Crystal samples may be used to obtain
partial information about fabricational imperfections.These results allow
one to specify critical parameters for the fabrication of Photonic Crystals.
[1] E.Silberstein, P.Lalanne, J.-P.Hugonin and Q.Cao J.Opt.Soc.Am.A
18 2865 (2001)
HL 12.32 Mo 16:30 Poster A
2D photonic crystal slab structures of high refractive index
in inorganic glasses — •Karolin Preusser-Mellert 1 , Markus
Schmidt 1 , Gunnar Boettger 1 , Uwe Huebner 2 , and Manfred
Eich 1 — 1 Technische Universität Hamburg-Harburg, Arbeitsbereich Materialien
der Elektrotechnik und Optik, Eissendorfer Str. 38, D-21073
Hamburg, Germany — 2 Institut für Physikalische Hochtechnologie e. V.,
Abt. Magnetik/Quantenelektronik, Winzerlaer Str. 10, D-07745 Jena,
Germany
Semiconductors are common materials used for fabricating twodimensional
photonic crystals because of their high refractive index and
the existing fabrication technology. But as it comes to integrate photonic
crystal structures, these high refractive index materials show larger
coupling losses than lower index systems. We have found an alternative
way of realizing a high vertical index contrast: We use inorganic glasses
as a waveguiding material with a relatively high refractive index - such
as titanium dioxide (n=2.5) - and we increase the vertical index contrast
with the help of a very low refractive index material: mesoporous
silica (n=1.14). This approach combines the advantages of air-bridgestructures
and solid substrates excluding their drawbacks. First structures
and simulations are presented.
HL 12.33 Mo 16:30 Poster A
Characterization and Structure Determination of Mesoporous
Silica Films for Optical Applications — •Denan Konjhodzic 1 ,
Markus Schmidt 2 , Helmut Bretinger 1 , Manfred Eich 2 , and
Frank Marlow 1 — 1 Max-Planck-Institut für Kohlenforschung, D-
45470 Mülheim an der Ruhr — 2 TU Hamburg-Harburg, D-21077 Hamburg
Mesoporous silica thin films were synthesized in a sol-gel process using
a nonionic triblock copolymer PEO-PPO-PEO as a template. Due to high
pore volume of these films, the effective index of refraction is very low
(n=1.14 at 1300 nm determined by the prism coupling method). Because
of their high mechanical, chemical and thermal stability, high optical
transparency, low optical scattering and especially because of the very
low refractive index, these films are useful as substrates for 2D photonic
crystals.
SAXS diffraction patterns obtained with an area detector clearly show
a partially ordered structure of the channels in one type of as-synthesized
films with a spacing of about 8 nm. There is no preferred direction of
the channels parallel to the surface, which is in agreement with optical
measurements. Other types of pore ordering have also been found. Calcination
leads to the shrinkage of the structure. Surface properties have
been investigated using AFM. The film surface is very smooth (roughness
below 1 nm) but with certain defects in one structure type.
Based on these findings we propose structure models for our mesoporous
films and for the defects inside. We discuss their implications for
photonic crystal research.
HL 12.34 Mo 16:30 Poster A
Crystal orientation dependence of pores in InP for photonic
crystal applications — •Stefan Lölkes, Sergiu Langa, Jürgen
Carstensen, and Helmut Föll — Technische Fakultät, Christian-
Albrechts-Universität zu Kiel, Kaiserstr. 2, 24143 Kiel
For the field of Photonic Crystals (PhCs), electrochemically etched
macroporous Si has set milestones[1]. All III/V semiconductor based
PhCs have so far been produced by plasma-etching. In 2003, Langa et
al.[2] showed uniform electrochemical pore etching in InP with tremendous
aspect ratios for 2D InP PhCs. To produce PhCs with a full 3D
photonic band gap, several authors have proposed fabrication methods
where first a set of slanted pores is drilled electrochemically [3], followed
by highly directional dry etching to introduce a second pore set orthog-