Super- and sub-radiance with atoms around an optical

Princeton-TAMU Symposium on Quantum Physics and Engineering,

in honor of Wolfgang Schleich June 2017

Luis A. Orozco www.jqi.umd.edu

Super- and sub-radiance with atoms around an optical

nanofibers

Graduate Students: J. A. Grover, J. E. Hoffman, S. Ravets (I. d’Optique), P. Solano, B. Patterson. Undergraduate Students: U. Chukwu, C. Ebongue, E. Fenton, B. Friedman, X. Gutierrez, A. Kahn, P. Kordell, E. Magnan, A. Preciado, J. D. Wong-Campos, A. Wood. Professors and Researchers: P. Barberis Blostein, F. K. Fatemi, L. A. Orozco, W. D. Phillips, S. L. Rolston University of Maryland, Institute D’Optique, National Institute of Standards and Technology, Army Research Laboratory, Universidad Nacional Autonoma de Mexico. Supported by: Atomtronics MURI from ARO, DARPA, the Fulbright Foundation, NSF through PFC@JQI, JQI, and ONR.

Christiane Xavier

5 2013

Jeff, Krysten Peter Uchenna Pablo, Jonathan, David

Eliot Alan

6 2015

Sylvain

Jonathan Jeff

3 2012

THE TEAMAdnan

9 2015

Pablo Jeff

102014

1 2016 Burkley

Optical Nanofibers

Optical Nanofibers

Core φ ~ 5 µm Cladding φ ~ 125 µm

Optical Nanofibers



Optical Nanofibers


Optical Nanofibers

50 nm away from the surface 1 atom can block 10% of the light.

Optical Density

Evanescent Coupling γ rad

γ1D Nottoscale

γTot = γ rad +γ1D

Nottoscale

A(!r ) = PI(!r )

α(!r ) = γ1D (!r )

γ0=1neff

σ 0

A(!r )=1neff

OD1(!r )

ONF Single Atom Optical Density

Can we see a collective atomic effect of atoms around the

nanofiber?

Infinite Range Interactions

Not to scale


Not to scale


Not to scale


Vfree ∝exp(ikr)kr


Vfree ∝exp(ikr)kr

V1D ∝ exp(ikr)


Vfree ∝exp(ikr)kr

V1D ∝ exp(ikr)

Super- and Sub-radiance (a classical explanation)

“When two organ pipes of the same pitch stand side by side, complications ensue which not infrequently give trouble in practice. In extreme cases the pipes may almost reduce one another to silence. Even when the mutual influence is more moderate, it may still go so far as to cause the pipes to speak in absolute unison, in spite of inevitable small differences. Lord Rayleigh (1877) in "The Theory of Sound".

Super- and Sub-radiance (a classical explanation)

We need the response of one oscillator due to a nearby oscillator (interference): !!a1 +γ0 !a1 +ω0

2a1 =32ω0γ0d̂1 ⋅

!E 2!r( )a1,

assuming a1 = a10 expi(ω − i / 2)t

γ = γ0 +32γ0Im d̂1 ⋅

!E 2!r( ){ }, with d̂1 ⋅

!E 2 0( ) = 2

3

ω =ω0 −34γ0 Re d̂1 ⋅

!E 2!r( ){ }

Observation of infinite-range interactions

Probe Beam

The idea behind the experiment

Probe Beam


We look for modifications of the radiative lifetime of an ensemble of atoms around the ONF.

Probe Beam

The sub- and super-radiant behavior depend on the phase relation of the atomic dipoles along the common mode


currentnanofiber

α =γ1Dγ0

Coupling Enhancement

Weuseuntrappedatoms!

Measuring the Radiative Lifetime

Measuring the Radiative Lifetime

1 mm

F=1F=2

F’=2F’=3

F’=1F’=0

De-pump Re-pump Probe

De-pump

Probe

Re-pump

Preparing the Atoms

F=1F=2

F’=2F’=3

F’=1F’=0

De-pump Re-pump Probe

Preparing the Atoms

20 30 40 50 60 70-30

-25

-20

-15

-10

-5

0

Atom-surface position [nm]

Frecuencyshift

[MHz] Δ

Δ

Atomic distribution with optical pumping

Distribution of atoms with optical pumping

0 50 100 150 200 2500.0

0.2

0.4

0.6

0.8

1.0

Atom-surface distance (nm)

Densitydistribution(arb.unit)

-4

-3

-2

-1

0

Log 10

cou

nt r

ate

0 5 10 15 20 25 30t/τ

0

Two distinct lifetimes

-4

-3

-2

-1

0

Log 10

cou

nt r

ate

0 5 10 15 20 25 30t/τ

0


τ ≈ 7.7τ 0

τ ≈ 0.9τ 0


τ ≈ 7.7τ 0

τ ≈ 0.9τ 0

-4

-3

-2

-1

0

Log 10

cou

nt r

ate

0 5 10 15 20 25 30t/τ

0

Decay time vs detunning

No radiation trapping for long lifetime

Decay time vs detunning

No radiation trapping for short lifetime

-4 -2 0 2 40.91.01.11.21.3

Δ/γ0

γ/γ 0

Pulse and signal ��

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0 5 10 15 20- 6

- 5

- 4

- 3

- 2

- 1

0

time (in units of τ0)

Log 1

0no

rmal

ized

coun

t ra

te

-4

-3

-2

-1

0

Log 10

cou

nt r

ate

0 5 10 15 20 25 30t/τ

0


τ ≈ 7.7τ 0

τ ≈ 0.9τ 0

N dependence

γsup = γ rad + Nγ1D

N dependence


Superradiance depends on the atom number!

Measurment of N

-20 -10 0 10 200.6

0.7

0.8

0.9

1.0

frequency (MHz)

Transmission

Probe

OD = N ⋅OD1(!r0 )

The slope (0.02) is smaller than γ1D (0.10) because it is an average over different realizations, non all of them superradiant.

Sub-radiance???


Infinite-range subradiance is limited!

Subradiance???

γ sub = γ rad −γ1D


γ radγ1D

-4

-3

-2

-1

0

Log 10

cou

nt r

ate

0 5 10 15 20 25 30t/τ

0

Sub-radiance??? γ rad

γ1D

γ ≈ 0.13γ0

γ sub = γ rad −γ1D ≈ 0.9γ0

The subradiant decay rate we measure is too slow!

Understanding the Signal

Understanding the Signal

Polarization dependent signal

VerDcallypolarizedprobe Horizontallypolarizedprobe

Polarization dependent signal

Vertically polarized probe Horizontally polarized probe

Subradiant Signal

-  Interaction distance smaller than λ: all modes get cancelled.

-  Interaction distance greater than λ: only one mode gets cancelled

We measure

γ sub = γ rad −γ1D ≈ 0.9γ0γ sub = 0.13γ0

Super-radiant Signal

-  Interaction distance smaller than λ: all modes get enhanced.

-  Interaction distance greater than λ: only one mode gets enhanced

We measure

γsup = γ rad + Nγ1Dγsup =1.1γ0

Fitting the Simulation

-4

-3

-2

-1

0

Log 10

nor

mal

ized

cou

nt ra

te

-4-2024

Nor

mal

ized

Res

idua

ls

(a)

(b)

0

-1

-2

-3

-4

t/τ0

0 5 10 15 20 25 30

0 5 10 15 20

t/τ0

Log 10

nor

mal

ized

cou

nt ra

te

Fitting the Simulation

Long distance modification of the atomic radiation

Long distance modification of the atomic radiation

We have atomic densities low enough to observe mostly infinite-range interactions

nanofiber

Left MOT

Splitting the MOT in two

Right MOT

≈ 400λ

Right MOT

Left MOT

Both MOTs

Evidence of infinite-range interactions

Observations: About one in 50 of the decays is super-radiant. Quantitative agreement with simulations.

Summary •  We have seen collective atomic effects (sub- and

super- randiance) monitoring the mode of the nanofiber. Superadiance shows long-range dipole-dipole interactions (many times the wavelength) scaling with the optical density (number of atoms). Subradiance is between nearby atoms.

•  New platform for exploring long-range interactions. •  Many Body physics without the Markov

approximation.

Thanks!

Documents

Super- and sub-radiance with atoms around an optical