TY  - JOUR
A1  - Laiho, K.
A1  - Pressl, B.
A1  - Schlager, A.
A1  - Suchomel, H.
A1  - Kamp, M.
A1  - Höfling, S.
A1  - Schneider, C.
A1  - Weihs, G.
T1  - Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation
JF  - Nanotechnology
N2  - We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.
KW  - Parametric down-conversion
KW  - Entanglement
KW  - CHIP
KW  - PUMP
KW  - Bragg-reflection waveguide
KW  - Information
KW  - phasematching
KW  - group refractive index
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187025
VL  - 27
IS  - 43
ER  - 
TY  - JOUR
A1  - Estrecho, E.
A1  - Gao, T.
A1  - Brodbeck, S.
A1  - Kamp, M.
A1  - Schneider, C.
A1  - Höfling, S.
A1  - Truscott, A. G.
A1  - Ostrovskaya, E. A.
T1  - Visualising Berry phase and diabolical points in a quantum exciton-polariton billiard
JF  - Scientific Reports
N2  - Diabolical points (spectral degeneracies) can naturally occur in spectra of two-dimensional quantum systems and classical wave resonators due to simple symmetries. Geometric Berry phase is associated with these spectral degeneracies. Here, we demonstrate a diabolical point and the corresponding Berry phase in the spectrum of hybrid light-matter quasiparticles—exciton-polaritons in semiconductor microcavities. It is well known that sufficiently strong optical pumping can drive exciton-polaritons to quantum degeneracy, whereby they form a macroscopically populated quantum coherent state similar to a Bose-Einstein condensate. By pumping a microcavity with a spatially structured light beam, we create a two-dimensional quantum billiard for the exciton-polariton condensate and demonstrate a diabolical point in the spectrum of the billiard eigenstates. The fully reconfigurable geometry of the potential walls controlled by the optical pump enables a striking experimental visualization of the Berry phase associated with the diabolical point. The Berry phase is observed and measured by direct imaging of the macroscopic exciton-polariton probability densities.
KW  - Berry phase
KW  - diabolical points
KW  - quantum billiard
KW  - exciton-polariton
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-167496
VL  - 6
IS  - 37653
ER  -