Mid-term Strategic ConferenceGranada, Spain, Nov. 13-14, 2019
CUSPIDOR: CMOS Compatible Single PhotonSources based on SiGe Quantum Dots
Thomas Fromherz
This project has received funding from the European Union’sHorizon 2020 research and innovation programme
under grant agreement No 731473.
Introduction
Integrated quantum optics at telecom wavelengths
I SOI integrated optic extremelymature
I can compact quantum opticalsources be added to establish SOIintegrated quantum optics in thetelecom wave length region ?
I currently: elaborate buildingblocks based on spontaneous4-wave mixing, externally pumped
I SiGe quantum dots as quantumoptical sources ?
Intel Silicon Photonics 100 Gb/s optical transceiver
Inset: Device A1 and B1
Laser input
SPDs RF CMOS electronic logic
N SiliconPhCW’s
IntegratedAWG’s
Fibre delay Low-loss PLZTNx2 switch
Sub-Poissonianheralded singlephoton output
Noiseport
NX
2 O
PTIC
AL S
WIT
CH
n0 ng n0
I P S
SFWM
M.J. Collins et al., Integrated spatial multiplexing ofheralded single-photon sources, Nat. Com. 4: 2582(2013)
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Main objectives
O1: A room-temperature electrically driven, optical matrix-element enhanced,silicon- germanium quantum dot based deterministic single photon source(SPS) with a generation rate of 50 MHz, with a second-order correlationfunction, g (2)(0) < 0.05 at cryogenic temperatures (∼ 10K) andg (2)(0) < 0.2 at room temperature, unprecedented for these type ofquantum dots;
O2: A single photon source based on the unconventional photon blockade(UPB), with a generation rate of 10 MHz and g (2)(0) < 0.05 at cryogenictemperatures (∼ 10K) and g (2)(0) < 0.2 at room temperature.
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Consortium
Johannes Kepler University Linz Austria T. Fromherz
Universita degli Studi di Pavia Italy D. Gerace
Cork Institute of Technology Ireland L. O’Faolain
Masaryk University Brno CzechRepublic
P. Klenovsky
Tyndall National Institute Ireland F. Murphy
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Role of partnersJohannes Kepler University Linz, Austria
I site controlled epitaxial growth ofSiGe based nanostructures
I defect engineered SiGe quantumdots (DEQDs)
I SOI integrated nano photonics
I project coordination
a
1 µm
b
c
1 µm
x
y x
y
z
Ge QD
airholeSi capping layer
pit
Ge wetting layer
mode M2
DEQD LED
2µm
µ-disc laser
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Role of partnersUniversita degli Studi di Pavia, Italy
I quantum photonics theory
I photonic nanostructuressimulations
I quantum optical spectroscopyand characterization in thetelecom band.
2μm
Energy (meV)793 800 806 812 817 822
0
0.5
1
RS
Int
ensi
ty (
arb.
)
M1
M2 M3 M4M5
M6
M1 M2 M3
M4 M5 M6
|E |y2
a',r'
a,r
Frequency comb
Unconventional photon blockade, pulsed excitation
UPB, photonic moleculeThe “bichromatic” cavity
Marco Clementi - University of Pavia 8/20
a’/a= 0.857
a’/a= 0.96
Alpeggiani et al., Appl. Phys. Lett. 107 (2015)
FDTD|E|2
Model|cn|2
Gaussian mode envelope(fundamental mode)
Simbula et al., APL Photonics 2 (2017)
Bichromatic cavity
FS
R ( m
ΓΓ
-FSR-FSR
Selective tuning of comb-modesSolutions
Marco Clementi - University of Pavia 16/20
Increase linewidth(introduce losses)
Selective tuning of the resonant modes
Portalupi et al., Opt. Express 18 (2010)Chen et al., Opt. Express 19 (2011)
Laser inducedlocal oxidation
5
Role of partnersCork Institute of Technology, Ireland
I doping of p-i-n structures
I nano-structuring of state-of-artphotonic devices
I integrated nano-optical systems
6
Role of partnersMasaryk University Brno, Czech Republic
I interfaceing mircoscopic andmesoscopic simulation methods
I mesoscopic energy level simulations inSiGe DEQDs including strain
I multi-particle effects
Simulated SiGe QD structure
3/17
Simulated SiGe QD had a shape of pyramid with base length of 20 nm and height of 2.5 nm. The whole structure is situated in Si; g.s. means ground state in the figure below. The electrons in the dot were considered to have a constant mixture of pure Γ Ge character and that for intersticial being mixed between Γ and X or L bands (this was provided by DFT).
QD
electron g.s.
hole g.s.
Simulated SiGe QD structure
3/17
Simulated SiGe QD had a shape of pyramid with base length of 20 nm and height of 2.5 nm. The whole structure is situated in Si; g.s. means ground state in the figure below. The electrons in the dot were considered to have a constant mixture of pure Γ Ge character and that for intersticial being mixed between Γ and X or L bands (this was provided by DFT).
QD
electron g.s.
hole g.s.
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Role of partnersTyndall National Institute, Ireland
I ab initio electronicstructure calculationsof the implanted Gedefect levels
I simulations ofimplanted Si, Sn, Sbdefects
I develop interface formesoscopick · p−simulations
I transport simulationssingle DEQD pin diode
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Main progress
I fabrication of bichromaticcavities with comb-likespectrum, Q >1M and recordfinesse (Si only)
I permanent tuning of modes inbicromatic photonic crystalcavities with ultra high Q
2μm
Energy (meV)793 800 806 812 817 822
0
0.5
1
RS
Int
ensi
ty (
arb.
)
M1
M2 M3 M4M5
M6
M1 M2 M3
M4 M5 M6
|E |y2
a',r'
a,r
Frequency comb
Quality factors
Marco Clementi - University of Pavia 21/20
Highest Q factor:Q ≈ 1.1 × 106 (fabrication limited)
Average Q is reduced by far-field optimization toQ ≈ 2 × 105 (load limited)
1560.855 1560.860 1560.8650
1
2
Bichromatic cavityN=48, a=410nm, R=100nm, r'=59nm, ff=0nm
Experimental points Fano fit
RS
sign
al (a
.u.)
Wavelength (nm)
Mode n. 1λ=1560.861 nmQ=1.1x106
Solutions
Marco Clementi - University of Pavia 16/20
Increase linewidth(introduce losses)
Selective tuning of the resonant modes
Portalupi et al., Opt. Express 18 (2010)Chen et al., Opt. Express 19 (2011)
FS
R ( m
ΓΓ
-FSR-FSR
Selective tuning of comb-modesSolutions
Marco Clementi - University of Pavia 16/20
Increase linewidth(introduce losses)
Selective tuning of the resonant modes
Portalupi et al., Opt. Express 18 (2010)Chen et al., Opt. Express 19 (2011)
Laser inducedlocal oxidation
9
Main progress
I site controlled growth of Geimplanted SiGe DEQDs
I nucleation sites in registry withbichromatic PhC design
I realistic DFT modelling of Gesplit-[110] interstitial, tracing backincrease of optical oscillatorstrength observed in experiments
I multi-scale modeling: k · p bandstructure parameters for Gesplit-[110] bands from DFTsimulations
15000 10000 5000 0 5000 10000 15000
10000
7500
5000
2500
0
2500
5000
7500
10000
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Key challenges
I achieving ultra large Q-factors in Ge containing PhC cavities. New route:growth of a single QD per cavity on a 2D wetting layer
I demonstrate single photon emission of DEQDs
I reduce spectral drift resulting in large linewidths of SiGe QDs
I combine large Q factor cavities with contacts for pin diodes
I achieve efficient current injection into single DEQDs embedded in a pindiode
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Dissemination and valorization
List of papers and conference contributions can be found on CUSPIDORhomepage http://www.cuspidor-quantera.eu
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