PLMCN‘10 Bloch-Polaritons in Multiple Quantum Well Photonic Crystals David Goldberg 1, Lev I....
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Transcript of PLMCN‘10 Bloch-Polaritons in Multiple Quantum Well Photonic Crystals David Goldberg 1, Lev I....
PLMCN‘10
Bloch-Polaritons in Multiple Quantum Well Photonic Crystals
David Goldberg1, Lev I. Deych1, Alexander Lisyansky1, Zhou Shi1, Vinod M. Menon1
Vadim Tokranov2, Mikhail Yakimov2, Serge Oktyabrsky2
1 Laboratory for Nano and Micro Photonics (LaNMP)Department of Physics, Queens College & Graduate Center of CUNY, USA.
2College of Nanoscale Science and Technology, University at Albany SUNY, USA.
Acknowledgement: United States Air Force Office of Scientific Research
Superradiance
Dicke: collection of closely spaced emitters form superradiant states. [R. H. Dicke,“Coherence in spontaneous radiation process,” Phys. Rev. 93, 99 (1954)]
Atoms in optical lattice used for demonstrating this effect. [S. Inouye et al. “Superradiant Rayleigh scattering from a Bose-Einstein condensate,” Science 285, 575 (1999) and others]
Quantum dot ensemble - Coupling between the excitons via their common radiative field.
[Scheibner et al. “Superradiance of quantum dots,” Nature Physics 3, 106 (2007)]
λ
Superradiance to Photonic Bandgap What happens when the number of emitters become very large?
- Superradiant mode to Photonic Bandgap
Atomic lattice used for demonstrating this effect. [ I. H. Deutsch et al. “Photonic bandgap in optical lattice,” Phys. Rev. A 52 1394 (1995); G. Birkl et al. Bragg scattering from atoms in optical lattice,” Phys. Rev. Lett. 75 2823 (1995)]
Excitonic lattice – semiconductor analog of atomic lattice. [M. Hubner et al. “ Optical lattices achieved by excitons in perodic quantum well structures,” Phys. Rev. Lett. 83 2851 (1999)]
In0.04Ga0.96As/GaAs QW lattice
Prineas et al., PRB (2000)
Emitters are periodically arranged with a half-wavelength periodicity (Bragg condition)
Light-matter interaction is between the excitons and vacuum photons.In0.04Ga0.96As/GaAs MQWs
Hübner et al., PRL (1999)
Exciton Lattice Polaritons
DBRs – 1D Photonic Crystals
n1
n2
Δn
Growth Direction
Exciton Lattice + Photonic Crystals
• Non-negligible refractive index contrast background, • Interaction between Bloch modes of photonic crystal and
excitonic lattice.
What happens when an excitonic lattice is also a photonic crystal? And the excitonic frequency is in resonance with photonic crystal Bloch states.
Formation of a hybrid bandgap with a narrow propagation band within the bandgap. The hybrid bandgap is wider than the individual bandgaps
Resonant Photonic Crystals
λ
Bragg bandgap
Excitonic bandgap
Reflect
ivit
y
Hybrid bandgap
MQW system
Exciton Lattice Bloch-Polaritons
ω
k//
ω0
ω+
ω-
Ω+
Ω-
04
2
00
Effect of refractive index modulation
2
)sincos()sin()cot(
)(
SiKdNKd
SR
Si
So
E. L. Ivchenko, A. I. Nesvizhskii, and S. Jorda, Phys. Solid State (1994)Erementchouk et al., PRB (2006)
Strong Coupling
Strong Coupling → Anti-crossing accompanied by bandgap enhancement
Strong Coupling → Anti-crossing
Microcavity Polaritons: Strong coupling is manifested in a typical anti-crossing behavior of the cavity mode and the exciton.
ω
k//
Erementchouk et al., PRB (2006)
ω
k//
ω0
ω+
ω-
Ω+
Ω-
Excitonic Lattice Bloch-Polaritons: Dispersion is described by two bandgaps: one attributed to the excitonic lattice and the other to the photonic crystal.
Weisbuch et al, PRL (1992)
Double-Quantum-Well (DQW) Basis: We used a structure with a DWQ basis. The DQWs allows for a greater Stark shift than compared to single QWs.
Geometry: The QWs are 3.5nm wide. A thin barrier of 1.6nm separates the paired QWs. The overall periodicity of the structure is 108.2nm.
Al0.22Ga0.78As/GaAs
35 Å 16 Å
1082 Å
Structure
Soubusta, et al, PRB, 1999
Modified Dispersion of Bloch-Polaritons
GaAs/AlGaAs QW system
Angle Dependent Reflectivity
In the vicinity of resonance, we observe broadening of the bandgap due to the formation of the mixed excitonic-photonic bandgap Slowing of the dispersion. Dramatic increase in reflectivity in the vicinity of the excitons.
10K
Goldberg…VMM et al, Nature Photonics 3, 662 (20009)
Experimental Dispersion
lh
hh
Polariton Dispersion
Strong coupling between the light-hole-exciton (e-lh1) and the low frequency photonic bandedge.
The heavy-hole-excitons (e-hh1) couple to propagating mode manifested by increase in reflectivity and formation of third polariton branch.
Goldberg…VMM et al, Nature Photonics 3, 662 (20009)
Polariton Dispersion
Three coupled oscillator model Mixing Coefficients
Ωlh-photon ~ 4.3 meVΩhh-photon ~ 6.2 meV
Electric Field Tuning of Polaritons
740 750 760 770 780 790
Refl
ectiv
ity (a.
u.)
Wavelength (nm)
12.5o(a)
740 750 760 770 780 790
Wavelength (nm)
35o(b)
740 750 760 770 780 790
0 kV/cm
Wavelength (nm)
55o
13.0 kV/cm
(c)
Electric Field Tuning of Polaritons
Ref
lect
ivity
(a.
u.)
0 kV/cm 2.6 kV/cm 5.2 kV/cm 7.8 kV/cm 10.4 kV/cm 13.0 kV/cm
740 750 760 770 780 790
Ref
elct
ivity
(a.
u.)
Wavelength (nm)
0 kV/cm 3.9 kV/cm 7.8 kV/cm 10.4 kV/cm
1.595
1.600
1.605
1.610
1.615
1.620
1.625
1.630
Ene
rgy
(eV
)
0 2 4 6 8 10 121.595
1.600
1.605
1.610
1.615
1.620
1.625
1.630
Ene
rgy
(eV
)
Electric Field (kV/cm)
Reflectivity Tuning
740 745 750 755 760 765 770 775 780 785 790
R
efle
ctiv
ity (
a.u.
)
Wavelength (nm)
0 kV/cm 2.6 kV/cm 5.2 kV/cm 7.8 kV/cm 10.4 kV/cm 13.0 kV/cm
770 771 772
0.4
0.6
0.8
1.0
>100% Spectral tuning
using quantum confined Stark effect.
~ 100% reflection change for small fields.
Use of double quantum well enhances the effect.
Summary
Demonstrated strong coupling between Bloch and excitonic modes in a photonic crystal incorporating an excitonic lattice Bandgap enhancement Large increase in the reflectivity in the vicinity of the exciton Formation hybrid lh-hh-Bloch-ELPs Slow dispersion for application in slow light, low threshold
nonlinear optics.
Electric field tuning of hybrid polariton states.
Significant change in reflectivity by tuning the polaritons.
L to R: Vasilios Passias, Warren Cheng, Tinya Cheng, Nischay Kumar, Mathew Luberto, Subhasish Chatterjee, Saima Husaini, David Goldberg, Jonathan Yip, Nikesh Valappil, and Vinod MenonMissing: Harish Natarajan, Nicky Okoye
http://www.lanmp.org [email protected]