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Guillaume TAREL, PhC Course, QD EMISSION 1
Control of spontaneous emission
of QD using photonic crystals
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Guillaume TAREL, PhC Course, QD EMISSION 2
Radiative transition -> Spontaneous emission
All light sources except lasers
+excitedemitter
environment
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Guillaume TAREL, PhC Course, QD EMISSION 3
Excited emitter -> emission of a photon after a characteristic lifetime
+excitedemitter
environment
=
Radiative transition -> Spontaneous emission
All light sources except lasers
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Guillaume TAREL, PhC Course, QD EMISSION 4
A lot of interest in modifying spontaneous emission
-Faster emission: Integrated photonics, high speed light sources
- Single photon sources: Quantum optics, Quantum criptography
- Better emission coupling factor
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Guillaume TAREL, PhC Course, QD EMISSION 5
Emitter : dimensionality of structures
Baier M., PhD Thesis, 2005
Spatial Variations of band edge for carriers (e and h)
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Nanopyramids of Gallium Arsenide
Guillaume TAREL, PhC Course, QD EMISSION 6
Control Spontaneous emission (SE)
Quantum dot: 3D confinment atomic like emitter
Low extraction efficiency: Absorption+reflected part+ even total intern reflection
%
Easy incorporation in devices
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Guillaume TAREL, PhC Course, QD EMISSION 7
« By intentionnaly placing boundaries close to a radiative system, one realize new situations in which excited state decay can be either supressed, greatly enhanced, or even made reversible .»
S. Haroche, 1990, Fundamental systems in Quantum Optics
-> Cavity Quantum Electrodynamic
Environment ?+
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Guillaume TAREL, PhC Course, QD EMISSION 8
iEbi fEaf
)(. rE
)()()(
22
baifE
if
f
ErEEr
F. Krauss Science 20 May 2005: 1122-1123
Cavity decay rate > QD cavity coupling strength
SE rate calculated from fermi golden rule…
Weak coupling
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Guillaume TAREL, PhC Course, QD EMISSION 9
-> on-resonance enhanced of resonance supressed
See e.g. Andreani et Al., Physica status solidi. B.
mode volumes and Q factor
2
2
)()(
)()(~
peakpeak rEr
rdrErV
0Q
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Guillaume TAREL, PhC Course, QD EMISSION 10
Purcell effect
-> Tailoring spontaneous emission
E.M.Purcell Phys. Rev. 69 (1946) p. 681
mode3
3
24
3
V
Q
nF cavcav
Vahala, Nature 2003
Excited emitter -> emission of a photon after a characteristic lifetimePurcell effect reduces spontaneous emission lifetimeProperties of the emitter modified but not fundamentally altered : weak coupling
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Guillaume TAREL, PhC Course, QD EMISSION 11
Low dimensionality structures
Photons confined by modulation of the refractive index: planar microcavity, photonic wires, micropillars, microdisks…
Vahala, Nature 2003
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Guillaume TAREL, PhC Course, QD EMISSION 12
Andreani et Al., Physica status solidi. B.
Photonic crystals
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Guillaume TAREL, PhC Course, QD EMISSION 13
QD+Photonic crystals
Both electrons and photons are confined in all dimensions
+
+
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Guillaume TAREL, PhC Course, QD EMISSION 14
Vahala Nature 424, 839-846 (2003)
M0 and M1 cavitys
Need small mode volumes
High Q – Small V
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Guillaume TAREL, PhC Course, QD EMISSION 15
Phys. Rev. Lett. 95, 013904 (2005)
Strauf et Al., Phys. Rev. Lett. 96, 127404 (2006)
Designs concepts holes position and size
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Guillaume TAREL, PhC Course, QD EMISSION 16
Yoshie et al., Nature 432, 200-203
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Guillaume TAREL, PhC Course, QD EMISSION 17
Andreani et Al., Physica status solidi. B.
0Q
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Guillaume TAREL, PhC Course, QD EMISSION 18
Phys. Rev. Lett. 95, 013904 (2005)
What is done:
1/ fabrication of structures : emitter embedded in photonic crystal
2/ try to find an emitter coupled to a cavity mode
Spectral + Spatial positioning
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Guillaume TAREL, PhC Course, QD EMISSION 19
Phys. Rev. B 71, 241304 (2005): Kress et al.
H1 PC cavity
Pronounced CQED effect
First example
r/a
r: hole radius
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Guillaume TAREL, PhC Course, QD EMISSION 20
Phys. Rev. B 71, 241304 (2005): Kress et al.
H1 PC cavity
Deeper shift in the bandgap
First example
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Guillaume TAREL, PhC Course, QD EMISSION 21
Phys. Rev. B 71, 241304 (2005): Kress et al.
Shortening of emission lifetime of around 5.6
H1 PC cavity
Maximum enhancement around 20
Max(photon lifetime) 2psTypical QD SE time 1 ns
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Guillaume TAREL, PhC Course, QD EMISSION 22
Phys. Rev. B 71, 241304 (2005): Kress et al.
H1 PC cavity
Shortening AND lengthening
Unpaterned membrane
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Guillaume TAREL, PhC Course, QD EMISSION 23
Phys. Rev. B 66, 041303 (2002): Happ et al.
Hexagonal defect microcavity H2 (7 missing holes, triangular lattice, filling factor 40%)
Ground state transition of the dots (170) Pump rate limited
4 of the defect modes of a H2 cavityHigh power no resolution of QD individual emission
2nd example
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Guillaume TAREL, PhC Course, QD EMISSION 24
Phys. Rev. B 66, 041303 (2002): Happ et al.
Hexagonal defect microcavity H2
Mode peaks emerge from the spectraLifetime limited, difference off/on resonance
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Guillaume TAREL, PhC Course, QD EMISSION 25
Phys. Rev. B 66, 041303 (2002): Happ et al.*9 SE rate enhancement due to purcell effect
on/off resonance
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Guillaume TAREL, PhC Course, QD EMISSION 26
Phys. Rev. Lett. 95, 013904 (2005)
What is done:
1/ fabrication of structures : emitter embedded in photonic crystal
2/ try to find an emitter coupled spectraly and spatially to a cavity mode
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Guillaume TAREL, PhC Course, QD EMISSION 27
One more step: « deterministic coupling» Light-matter coupling is no more due to chance
Badolato et al., Science 20 May 2005: 1158 - 1161
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Guillaume TAREL, PhC Course, QD EMISSION 28
Writing of the S1 PhC
Trace of the stacked QDs
Electric field intensity from FDTD calculations
-> high Q cavity mode resonance QD transition energy
BUT remains red shifted = approximate SPECTRAL COUPLING
Positionning of the QD
SPATIAL COUPLING
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Guillaume TAREL, PhC Course, QD EMISSION 29
Spectral tuning of the mode resonance
3 etching cycles
5 etching cycles
QD emission intensity is modified
Enhancement of radiative decay rate of around 5
Enlarge PC holes and thin PC membrane
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Guillaume TAREL, PhC Course, QD EMISSION 30
Strong coupling
Other really interesting aspects : Cavity decay rate < QD cavity coupling strength
Vahala, Nature 2003
Cavity decay rate > QD cavity coupling strength = Purcell effectModify spontaneous emission
CONCLUSION
Photonic crystals = tailoring of spontaneous emission using Purcell effect