Harnessing light-matter interaction in intersubband ... · Harnessing light-matter interaction in intersubband microcavities NEST CNR-INFM and Scuola Normale Superiore Pisa, Italy

SCUOLA NORMALE SUPERIORE

Harnessing light-matter interaction in intersubband microcavities

NEST CNR-INFM and Scuola Normale SuperiorePisa, Italy

Aji A. Anappara


People involved in this workDavid Barate, Alessandro Tredicucci, Lucia Sorba

and Fabio Beltram NEST CNR-INFM & Scuola Normale Superiore, Pisa, Italy

Simone De Liberato and Cristiano CiutiUniv. Paris 7-Denis Diderot, Paris, France

Giorgio BiasiolNEST CNR-INFM and Laboratorio TASC, Trieste, Italy

Jan Devenson, Roland Teissier

and Alexei BaranovIES, Montpellier II, France

Carl Hübler

and Rupert Huber Universitaet

Konstanz, Konstanz, Germany


Outline

Introduction and motivation

Strong-coupling regime using intersubband transitions

Manipulation of cavity electrodynamics

‘Ultra-strong coupling regime’ of light-matter interaction

Attempts to realize ultra-strong coupling regime

Conclusions


How intersubband

transitions interact with confined electromagnetic field?

Intersubband photonicsA

bsor

ptio

n

350

5−

x2

x2 150+

250 x

E

k||

“atomic-like”ultrafast relaxation time (~ps ) tailorable properties


Cavity QED

cavdg E=Transition-photon coupling,

coupling

Optical cavity light resonator⇒

Electronic transition material resonance⇒

Weak coupling Strong coupling

Perturbative regimePurcell effect

Rabi oscillations“cavity-polaritons”


Light-matter interaction

1

2

0ω1

2 2 Ω

0ωcavitymode ≡

electronic transition weak coupling strong coupling

⇒

1

2g

γ

κ


Strong-coupling regime

Solid state physics:

excitons (bulk, QWs or QDs in semiconductor microcavities)

qubits (cooper pair quantum-box in microwave resonators)

Atomic physics: atoms in metallic microcavity

R. J. Thompson et al., PRL.,68, 1132 (1992)


Exciton polaritons


Intersubband resonatorsTheoretical predictions by Ansheng

Liu, PRB., 55, 7101 (1997)

θintGaAs

substrate

cavity core

airθcav

z

DBR

QWs

air

DBR

substrate


Intersubband resonators

Ansheng

Liu, PRB 55, 7101 (1997)

Lcav

= 3μm; NDBR

= 3 GaAs/AlAs

DBRsTotal thickness ~ 14 μm


total-internal reflection geometryair as top-cladding

D. Dini

et.al, PRL., 90, 116401 (2003)

Intersubband polaritons

θ

AlAs

cavity core

60°

GaAssubstrate

Lcav

~ 3μm; θcav

= 60°;

NQW

= 18, doped to 5×1011cm-2

LAlAs

~ 4 μm;

Total thickness ~ 5 μm


0.850 0.855 0.860 0.865 0.870 0.875 0.880

110

120

130

140

150

160

170

angle θ (degrees)58.5 59.0 59.5 60.0 60.5 61.0 61.5 62.0

Ener

gy (m

eV)

sin(θ)

Intersubband polaritons

D. Dini

et.al, PRL., 90, 116401 (2003)

measurements at 10K

100 120 140 160 180

61.9861.6361.2560.6160.32

60.1360.0560.0059.7659.4959.2858.90

58.3858.37

58.20

Reflectance (a. u.)

Energy (meV) 12

, 2 14

, 140

Minimum splitting meV

ISBT energy meVω

Ω =

=


105 120 135 150 165 180

Ref

lect

ance

(a. u

.)

Energy (meV)

62.0

61.5

61.0

60.5

60.0

59.5

59.0

58.5

58.0

100 120 140 160

0.3

0.4

0.5

0.6

0.7

Ref

lect

ance

Energy (meV)

Coupled oscillators -

simulationElectromagnetic field propagation : Optical transfer matrix

Quantum well : ( ) ( )2 2

2 2

0 0 0

1

eff

Ne f Sin

m L i

θε ω ε

ε ω ω γω∞= +

− −

⎛ ⎞⎜ ⎟⎝ ⎠


Intersubband resonators

0 1 2 3 4 50.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Fiel

d In

tens

ity

Growth direction (μm)

Cladding (AlAs)

Active region m

etal

(Au)

0 1 2 3 4 5 6 7

0.0

0.1

0.2

0.3

0.4

Active regionFi

eld

Inte

nsity


cladding(AlAs)

air

0 1 2 3 4 5 6 7

0.0

0.1

0.2

0.3

0.4

Cladding (AlAs)

Fiel

d In

tens

ity


Cladding (AlAs)

Active region


Manipulation of cavity electrodynamics

intersubband polaritons, N → electron density

-

can be tuned externally !!

N → number of oscillators

Rabi splitting, NΩ∝


Depletion gating

Ohmic contacts

Schottky

gate

Cavity core

θ

n-doped

GaAsAlAs 3 quantum

wells

70°

A. A Anappara

et al., APL., 87, 051105 (2005)


Normal-mode splitting and anticrossing

90 100 110 120 130 140 150 160 170

Ref

lect

ance

(a.u

)

Energy (meV)

66.8967.0367.1867.3367.4767.6267.7767.9268.0768.2268.3768.4468.5268.6768.7468.8268.9769.1269.2769.4269.57

66.5 67.0 67.5 68.0 68.5 69.0 69.5 70.0112116120124128132136140144148

Ener

gy(m

eV)

Angle (θ)

12

, 2 13

, 137

Minimum splitting meV

ISBT energy meVω

Ω =

=

3300

QWsmeasured at K


Strong coupling to weak coupling

A. A Anappara

et al., APL., 87, 051105 (2005)

105 120 135 150

-6V-5.5V

-5V-4.5V

-4V-3.5V

-3V-2.5V

-2V-1.5V

-1VRef

lect

ance

(a. u

.)

Energy (meV)

zero V-0.5V

Room temperature measurementsResonant angle, θ

= 68.67°


Tunnel-assisted control of splitting

(b) 52 kV/cm

(c) 100 kV/cm

(a) Zero bias

A. A Anappara

et al., APL., 89, 171109 (2005)

Carriers are injected by tunneling


100 120 140 160 180 200

Ref

lect

ance

(a.u

.)

Energy(meV)

68.1767.8767.5767.2766.9666.6766.3666.0765.7765.4765.1864.8964.59

64.0164.30

(a) Zero field

50 100 150 200 250 300

120 140 160

Ref

lect

ance

(a.u

.)

Energy(meV)

-7V-6.5V

-6V-5.5V

-5V-4.5V

-4V-3.5V

-3V-2.5V

-2V-1.5V

-1V-0.5VzeroV

68.7868.4868.1767.8767.5767.2766.9666.6766.3666.0765.7765.4765.1864.8964.59

64.01

Ref

lect

ance

(a.u

.)

Energy(meV)

64.30

(b)100kV/cm

Tuning by tunnel coupling


Conclusions

Tailorability and manipulation of cavity electrodynamics

in intersubband microcavities

Intersubband microcavities are potential systems to realize

the unprecedented ‘ultra-strong coupling regime’

Novel device applications – high absorption QWIPs,

ultrafast optical switches, super luminescent devices

Documents

Harnessing light-matter interaction in intersubband ... · Harnessing light-matter interaction in intersubband microcavities NEST CNR-INFM and Scuola Normale Superiore Pisa, Italy