PLMCN‘10 Bloch-Polaritons in Multiple Quantum Well Photonic Crystals David Goldberg 1, Lev I. Deych 1, Alexander Lisyansky 1, Zhou Shi 1, Vinod M. Menon.

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]