guillaume tarel, phc course, qd emission 1 control of spontaneous emission of qd using photonic...

Guillaume TAREL, PhC Course, QD EMISSION 1

Control of spontaneous emission

of QD using photonic crystals


Radiative transition -> Spontaneous emission

All light sources except lasers

+excitedemitter

environment


Excited emitter -> emission of a photon after a characteristic lifetime

+excitedemitter

environment

=

Radiative transition -> Spontaneous emission

All light sources except lasers


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


Emitter : dimensionality of structures

Baier M., PhD Thesis, 2005

Spatial Variations of band edge for carriers (e and h)

Nanopyramids of Gallium Arsenide


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


« 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 ?+


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


-> 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


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


Low dimensionality structures

Photons confined by modulation of the refractive index: planar microcavity, photonic wires, micropillars, microdisks…

Vahala, Nature 2003


Andreani et Al., Physica status solidi. B.

Photonic crystals


QD+Photonic crystals

Both electrons and photons are confined in all dimensions

+

+


Vahala Nature 424, 839-846 (2003)

M0 and M1 cavitys

Need small mode volumes

High Q – Small V


Phys. Rev. Lett. 95, 013904 (2005)

Strauf et Al., Phys. Rev. Lett. 96, 127404 (2006)

Designs concepts holes position and size


Yoshie et al., Nature 432, 200-203


Andreani et Al., Physica status solidi. B.

0Q


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


Phys. Rev. B 71, 241304 (2005): Kress et al.

H1 PC cavity

Pronounced CQED effect

First example

r/a

r: hole radius



H1 PC cavity

Deeper shift in the bandgap

First example



Shortening of emission lifetime of around 5.6

H1 PC cavity

Maximum enhancement around 20

Max(photon lifetime) 2psTypical QD SE time 1 ns



H1 PC cavity

Shortening AND lengthening

Unpaterned membrane


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


Phys. Rev. B 66, 041303 (2002): Happ et al.

Hexagonal defect microcavity H2

Mode peaks emerge from the spectraLifetime limited, difference off/on resonance


Phys. Rev. B 66, 041303 (2002): Happ et al.*9 SE rate enhancement due to purcell effect

on/off resonance


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


One more step: « deterministic coupling» Light-matter coupling is no more due to chance

Badolato et al., Science 20 May 2005: 1158 - 1161


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


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


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

guillaume tarel, phc course, qd emission 1 control of spontaneous emission of qd using photonic...

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qd emission

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excited emitter emission

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qd photonic crystals