278 research outputs found
Optimal all-optical switching of a microcavity resonance in the telecom range using the electronic Kerr effect
We have switched GaAs/AlAs and AlGaAs/AlAs planar microcavities that operate
in the "Original" (O) telecom band by exploiting the instantaneous electronic
Kerr effect. We observe that the resonance frequency reversibly shifts within
one picosecond. We investigate experimentally and theoretically the role of
several main parameters: the material backbone and its electronic bandgap, the
pump power, the quality factor, and the duration of the switch pulse. The
magnitude of the shift is reduced when the backbone of the central
layer has a greater electronic bandgap; pumping with photon energies
near the bandgap resonantly enhances the switched magnitude. Our model shows
that the magnitude of the resonance frequency shift depends on the pump pulse
duration and is maximized when the duration matches the cavity storage time
that is set by the quality factor. We provide the settings for the essential
parameters so that the frequency shift of the cavity resonance can be increased
to one linewidth
Decoherence processes in a current biased dc SQUID
A current bias dc SQUID behaves as an anharmonic quantum oscillator
controlled by a bias current and an applied magnetic flux. We consider here its
two level limit consisting of the two lower energy states | 0 \right> and |
1 \right>. We have measured energy relaxation times and microwave absorption
for different bias currents and fluxes in the low microwave power limit.
Decoherence times are extracted. The low frequency flux and current noise have
been measured independently by analyzing the probability of current switching
from the superconducting to the finite voltage state, as a function of applied
flux. The high frequency part of the current noise is derived from the
electromagnetic environment of the circuit. The decoherence of this quantum
circuit can be fully accounted by these current and flux noise sources.Comment: 4 pages, 4 figure
Differential ultrafast all-optical switching of the resonances of a micropillar cavity
We perform frequency- and time-resolved all-optical switching of a GaAs-AlAs
micropillar cavity using an ultrafast pump-probe setup. The switching is
achieved by two-photon excitation of free carriers. We track the cavity
resonances in time with a high frequency resolution. The pillar modes exhibit
simultaneous frequency shifts, albeit with markedly different maximum switching
amplitudes and relaxation dynamics. These differences stem from the
non-uniformity of the free carrier density in the micropillar, and are well
understood by taking into account the spatial distribution of injected free
carriers, their spatial diffusion and surface recombination at micropillar
sidewalls.Comment: 4 pages, 3 figure
Optical characterization and selective addressing of the resonant modes of a micropillar cavity with a white light beam
We have performed white-light reflectivity measurements on GaAs/AlAs
micropillar cavities with diameters ranging from 1 {\mu}m up to 20 {\mu}m. We
are able to resolve the spatial field distribution of each cavity mode in real
space by scanning a small-sized beam across the top facet of each micropillar.
We spectrally resolve distinct transverse optical cavity modes in reflectivity.
Using this procedure we can selectively address a single mode in the multimode
micropillar cavity. Calculations for the coupling efficiency of a
small-diameter beam to each mode are in very good agreement with our
reflectivity measurements.Comment: 7 pages, 8 figure
7e conférence scientifique internationale sur la prévention des troubles musculosquelettiques, PREMUS 2010 (Angers, 29 août - 2 septembre 2010)
Mac Cune-Albright syndrome. Answer to the e-quid “Painful lameness in a child”
International audienc
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