Actual research project

3D photonic crystals allow to custom design the photonic density of states and therefore to omit spontaneous emission for certain wavelengths. This opens the possibility to study atom-photon bound states and new relaxation channels, which are not observable in vacuum. We fabricate 3D photonic crystals with complete gaps via different templating methods (e.g. artifical opals, laser direct writing) and subsequent Silicon or Tungsten inversion. PbS quantum dots are used as active medium emitting around 1.5um.
I am working on the modification of spontaneous and thermal emission from 3D photonic crystals. The samples as well as the active materials are fabricated and characterized in our group to get the best control on all parameters possible.

Contact

Work: Dept. of Chemistry
University of Toronto
Lash Miller Building
80, St. George Street
M5S3H6 Toronto , Canada
Office: Room LM 329
Fax : 416 971 2011
Email: gfreyman@chem.utoronto.ca

Curriculum vitae

1992-1998 studying physics at Universität Karlsruhe (TH) in Germany, focusing on near-field optics and semiconductor physics

1998-2001 Ph.D. student at Universität Karlsruhe (TH) in Germany in Martin Wegener's group. Research topics: low temperature near-field microscopy, influence of disorder on the emission properties and the excitonic energy level statistics in semiconductor quantum wells

2001-2002 PostDoc at the Institute for Nanotechnology at the Forschungszentrum Karlsruhe in Martin Wegener's group. Research topics: characterization of 2D and 3D photonic crystals via white-light interferometry, fabrication of 3D photonic crystals via laser holography and laser direct writing.

2003-… Joint PostDoc at the University of Toronto in the groups of Sajeev John and Geoffrey A. Ozin . Research topics: Thermal and spontaneous emission from 3D photonic crystals, fabrication and characterization of 3D photonic crystals, fabrication and characterization of PbS quantum dots.

List of publications

Computer simulations: Subwavelength resolution with an apertureless SNOM
G. von Freymann, Th. Schimmel, and M. Wegener,
Appl. Phys. A 66 , 5939 (1998)

Parallel computing on Near-field Scanning Optical Microscopy (NSOM)
G. von Freymann, Th. Schimmel, and M. Wegener,
in “High Performance Computing in Science and Engineering '98”, Springer (1998)

Computer simulations on near-field scanning optical microscopy: Can subwavelength resolution be obtained using uncoated optical fibre probes?
G. von Freymann, Th. Schimmel, and M. Wegener,
Appl. Phys. Lett. 73 (9), 1170 (1998)

Depolarization Near-field Scanning Optical Microscopy: Influence of Wavelength and Tip-Shape on the Lateral Resolution
G. von Freymann, M. Wegener, and Th. Schimmel,
Surface and Interface Analysis 27 , 499 (1999)

The Depolarization NSOM: Comparison of Experiment and Theory
G. von Freymann, Ch. Adelmann, G. Scheiber, Th. Schimmel, and M. Wegener
Journal of Microscopy 194 , 491 (1999)

Near-Field Photoluminescence Imaging of Single Defects in a ZnSe Quantum Well Structure at Low Temperatures
G. von Freymann, D. Lüerßen, C. Rabenstein, M. Mikolaiczyk, H. Richter, H. Kalt, Th. Schimmel, and M. Wegener
Appl. Phys. Lett. 76 , 203 (2000)

Statistical Analysis of Near-Field Photoluminescence Spectra of Single Ultrathin Layers of CdSe/ZnSe
G. von Freymann, E. Kurtz, C. Klingshirn, and M. Wegener
Appl. Phys. Lett. 77 , 394 (2000)

Autocorrelation spectroscopy on single ultrathin layers of CdSe/ZnSe: hints for a non-thermal distribution of excitons in quantum islands
G. von Freymann, E. Kurtz, C. Klingshirn, D. Litvinov, D. Gerthsen, Th. Schimmel, and M. Wegener,
Journal of Microscopy 202 , 218 (2001)

Hints for a non-thermal distribution of excitons in CdSe/ZnSe quantum islands.
von Freymann, G.; Kurtz, E.; Klingshirn, C.; Schimmel, Th.; Wegener, M.
Springer Proceedings in Physics 87 (Proceedings of the 25th International Conference on the Physics of Semiconductors, 2000, Part I ), 705 (2001).

Level repulsion in nano-photoluminescence spectra from single GaAs quantum wells.
G. von Freymann, U. Neuberth, M. Deubel, M. Wegener, G. Khitrova, and H. M. Gibbs
Phys. Rev. B. 65 , 205327 (2002)

Combining a scanning near-field optical microscope with a picosecond streak-camera: Statistical analysis of exciton kinetics in GaAs single quantum wells
U. Neuberth, L. Walter, G. von Freymann, B. DalDon, H. Kalt, M. Wegener, G. Khitrova, and H. M. Gibbs,
Appl. Phys. Lett. 80, 3340 (2002)

Spatial autocorrelation analysis of nanophotoluminescence images of single GaAs quantum wells.
Neuberth, U.; Walter, L.; von Freymann, G.; Schimmel, Th.; Wegener, M.; Khitrova, G.; Gibbs, H. M.
Applied Physics Letters 81 (10), 1881 (2002)

Investigations on phonon-assisted relaxation mechanisms in CdSe/ZnSe quantum islands using time-resolved near-field spectroscopy.
Dal Don, B.; Dianoux, R.; Wachter, S.; Kurtz, E.; Von Freymann, G.; Neuberth, U.; Klingshirn, C.; Wegener, M.; Kalt, H.
Physica Status Solidi A 190 (2), 533 (2002)

Influence of the quantum island distribution on relaxation of localized excitons in CdSe/ZnSe heterostructures.
Dal Don, B.; Dianoux, R.; Wachter, S.; Schmidt, M.; Kurtz, E.; Von Freymann, G.; Neuberth, U.; Klingshirn, C.; Wegener, M.; Kalt, H.
Physica Status Solidi B 229 (1), 463 (2002)

Autocorrelation spectroscopy on single GaInAs/GaAs quantum wells.
Neuberth, Ulrich; von Freymann, Georg; Wegener, Martin; Nau, Siegfried; Stolz, Wolfgang.
Physica Status Solidi B, 238 (3), 498 (2003)

Three-dimensional face-centered-cubic photonic crystal templates by laser holography: fabrication, optical characterization, and band-structure calculations.
Miklyaev, Yu. V.; Meisel, D. C.; Blanco, A.; von Freymann, G.; Busch, K.; Koch, W.; Enkrich, C.; Deubel, M.; Wegener, M.
Applied Physics Letters 82 (8), 1284 (2003)

Diffraction properties of two-dimensional photonic crystals.
von Freymann, G.; Koch, W.; Meisel, D. C.; Wegener, M.; Diem, M.; Garcia-Martin, A.; Pereira, S.; Busch, K.; Schilling, J.; Wehrspohn, R. B.; Gosele, U.
Applied Physics Letters 83 (4), 614 (2003)

 

Conference contributions

Poster: Computer simulations: subwavelength resolution with an apertureless SNOM
G. von Freymann, Th. Schimmel, and M. Wegener
9th International Conference on Scanning Tunneling Microscopy / Spectroscopy and Related Techniques, July 20-25, 1997, CCH Hamburg

ditto
Deutsch-Chinesischer Workshop über Rastersondentechniken, FZ Karlsruhe

Poster: Computersimulationen: Abbildungseigenschaften des Internal-Reflection SNOM
G. von Freymann, Th. Schimmel, M. Wegener, B. Hanewinkel, A. Knorr, and S. W. Koch
Frühjahrstagung der DPG 1998, Regensburg

Poster: Parallelrechner in der optischen Nahfeldmikroskopie
G. von Freymann, Th. Schimmel, and M. Wegener
First Workshop on High Performance Computing in Science and Engineering, June 22-24, 1998, HLRS Stuttgart

Poster: Computer simulations and experiments on the Depolarization-NSOM
(best poster award)
G. von Freymann, Ch. Adelmann, Th. Schimmel, and M. Wegener
International Summerschool in Nanophysics, August 11-20, 1998, Helsinki

Talk: The Depolarization NSOM: Subwavelength resolution with uncoated optical fiber probes
G. von Freymann, Ch. Adelmann, G. Scheiber, Th. Schimmel, and M. Wegener
5th International Conference on Near-Field Optics, nfo-5, December 2-6, 1998, Shirahama, Japan

Talk: Das Depolarisations SNOM: Nahfeldauflösung mit unbedampften Glasfaserspitzen
G. von Freymann, Ch. Adelmann, Th. Schimmel, and M. Wegener
Frühjahrstagung der DPG 1999, Münster

Talk: Nanocharakterisierung mit dem Nahfeldmikroskop
G. von Freymann, Th. Schimmel, and M. Wegener
Nano-Workshop, Institut für Nanotechnologie, 7. Juli 1999, Karlsruhe

Talk: Abbildung einzelner Defekte in einer ZnSe Quantentrogstruktur mittels Nahfeld-Photolumineszenz bei tiefen Temperaturen
G. von Freymann, D. Lüerssen, C. Rabenstein, M. Mikolaiczyk, H. Richter, H. Kalt, Th. Schimmel, M. Wegener, K. Okawa, D. Hommel
Frühjahrstagung der DPG 2000, Regensburg

Talk: Imaging of single defects in a ZnSe Quantum Well Structure with Nanophotoluminescence at low temperatures
G. von Freymann, D. Lüerssen, C. Rabenstein, M. Mikolaiczyk, H. Richter, H. Kalt, Th. Schimmel, M. Wegener, K. Okawa, and D. Hommel
International conference on quantum electronics and laser science, QELS 2000, San Francisco

Poster: Statistical analysis of near-field photoluminescence spectra of ultrathin layers of CdSe/ZnSe
G. von Freymann, E. Kurtz, C. Klingshirn, Th. Schimmel, and M. Wegener
International conference on near-field optics and related techniques, nfo-6, 27.8.-31.8.2000, University of Twente, The Netherlands

ditto
International conference on the physics of semiconductors, ICPS 25, 17.9.-22.9.2000, Osaka , Japan

Poster: Autokorrelationsspektroskopie an CdSe/ZnSe: Hinweise auf eine nicht-thermische Exzitonenverteilung in Quanten-Inseln
G. von Freymann, E. Kurtz, C. Klingshirn, Th. Schimmel, and M. Wegener
Frühjahrstagung der DPG 2001, Hamburg

Talk: Optische Nahfeld-Autokorrelationsspektroskopie an GaAs Einzelquantenfilmen
G. von Freymann, U. Neuberth, H.M. Gibbs, G. Khitrova, M. Wegener
Frühjahrstagung der DPG 2001, Hamburg

Talk: Autocorrelation optical near-field spectroscopy of single GaAs quantum wells
G. von Freymann, U. Neuberth, H.M. Gibbs, G. Khitrova, M. Wegener
International conference on quantum electronics and laser science, QELS 2001, Baltimore

Poster: Level repulsion in nanophotoluminescence spectra from single GaAs quantum wells
G. von Freymann, U. Neuberth, M. Deubel, M. Wegener, G. Khitrova, and H. M. Gibbs
26th International conference on the physics of semiconductors ICPS, 2002, Edinburgh

Talk: Polarisation Dependent Coupling in Ring Resonator Filters
G.-A. Chakam, W. Freude, C. Poulton, G. von Freymann, M. Wegener, and M. Fujii
15th Annual Lasers and Electro Optics Society Meeting, 2002, Glasgow

Poster: Fabrication of 3D fcc Photonic Crystal Templates by Holography
G. von Freymann, D. C. Meisel, Yu. Miklyaev, W. Koch, M. Wegener, K. Busch
Photonic and Electromagnetic Crystal Structures PECS-IV, October 28-31, 2002 Los Angeles , California , USA

Talk: Angle- and spectrally-resolved Bragg scattering on two-dimensional silicon-based photonic crystals
G. von Freymann, K. Busch, M. Diem, A. Garcia-Martin, U. Gösele, W. Koch, D.C. Meisel, S. Pereira , J. Schilling, M. Wegener, R. Wehrspohn 
International conference on quantum electronics and laser science QELS 2003, Baltimore

 

 

 

 

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