83 research outputs found
Efficient Spatial Redistribution of Quantum Dot Spontaneous Emission from 2D Photonic Crystals
We investigate the modification of the spontaneous emission dynamics and
external quantum efficiency for self-assembled InGaAs quantum dots coupled to
extended and localised photonic states in GaAs 2D-photonic crystals. The
2D-photonic bandgap is shown to give rise to a 5-10 times enhancement of the
external quantum efficiency whilst the spontaneous emission rate is
simultaneously reduced by a comparable factor. Our findings are quantitatively
explained by a modal redistribution of spontaneous emission due to the modified
local density of photonic states. The results suggest that quantum dots
embedded within 2D-photonic crystals are suitable for practical single photon
sources with high external efficiency
Highly efficient single photon emission from single quantum dots within a two-dimensional photonic bandgap
We report highly efficient single photon generation from InGaAs
self-assembled quantum dots emitting within a two-dimensional photonic bandgap.
A strongly suppressed multiphoton probability is obtained for single quantum
dots in bulk GaAs and those emitting into the photonic bandgap. In the latter
case, photoluminescence saturation spectroscopy is employed to measure a ~17
times enhancement of the average photon extraction efficiency, when compared to
quantum dots in bulk GaAs. For quantum dots in the photonic crystal we measure
directly an external quantum efficiency up to 26%, much higher than for quantum
dots on the same sample without a tailored photonic environment. The results
show that highly efficient quantum dot single photon sources can be realized,
without the need for complex nanopositioning techniques
Dephasing of quantum dot exciton polaritons in electrically tunable nanocavities
We experimentally and theoretically investigate dephasing of zero dimensional
microcavity polaritons in electrically tunable single dot photonic crystal
nanocavities. Such devices allow us to alter the dot-cavity detuning in-situ
and to directly probe the influence on the emission spectrum of varying the
incoherent excitation level and the lattice temperature. By comparing our
results with theory we obtain the polariton dephasing rate and clarify its
dependence on optical excitation power and lattice temperature. For low
excitation levels we observe a linear temperature dependence, indicative of
phonon mediated polariton dephasing. At higher excitation levels, excitation
induced dephasing is observed due to coupling to the solid-state environment.
The results provide new information on coherence properties of quantum dot
microcavity polaritons.Comment: Figure 2, panel (b) changed to logarithmic + linear scal
Enhanced photoluminescence emission from two-dimensional silicon photonic crystal nanocavities
We present a temperature dependent photoluminescence study of silicon optical
nanocavities formed by introducing point defects into two-dimensional photonic
crystals. In addition to the prominent TO phonon assisted transition from
crystalline silicon at ~1.10 eV we observe a broad defect band luminescence
from ~1.05-1.09 eV. Spatially resolved spectroscopy demonstrates that this
defect band is present only in the region where air-holes have been etched
during the fabrication process. Detectable emission from the cavity mode
persists up to room-temperature, in strong contrast the background emission
vanishes for T > 150 K. An Ahrrenius type analysis of the temperature
dependence of the luminescence signal recorded either in-resonance with the
cavity mode, or weakly detuned, suggests that the higher temperature stability
may arise from an enhanced internal quantum efficiency due to the
Purcell-effect
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