super- and sub-radiance with atoms around an optical
TRANSCRIPT
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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
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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.
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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
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Optical Nanofibers
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Optical Nanofibers
Core φ ~ 5 µm Cladding φ ~ 125 µm
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Optical Nanofibers
Core φ ~ 5 µm Cladding φ ~ 125 µm
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Core φ ~ 5 µm Cladding φ ~ 125 µm
Optical Nanofibers
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Core φ ~ 5 µm Cladding φ ~ 125 µm
Optical Nanofibers
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50 nm away from the surface 1 atom can block 10% of the light.
Optical Density
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Evanescent Coupling γ rad
γ1D Nottoscale
γTot = γ rad +γ1D
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Nottoscale
A(!r ) = PI(!r )
α(!r ) = γ1D (!r )
γ0=1neff
σ 0
A(!r )=1neff
OD1(!r )
ONF Single Atom Optical Density
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Can we see a collective atomic effect of atoms around the
nanofiber?
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Infinite Range Interactions
Not to scale
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Infinite Range Interactions
Not to scale
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Infinite Range Interactions
Not to scale
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Infinite Range Interactions
Vfree ∝exp(ikr)kr
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Infinite Range Interactions
Vfree ∝exp(ikr)kr
V1D ∝ exp(ikr)
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Infinite Range Interactions
Vfree ∝exp(ikr)kr
V1D ∝ exp(ikr)
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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".
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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( ){ }
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Observation of infinite-range interactions
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Probe Beam
The idea behind the experiment
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Probe Beam
The idea behind the experiment
We look for modifications of the radiative lifetime of an ensemble of atoms around the ONF.
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Probe Beam
The sub- and super-radiant behavior depend on the phase relation of the atomic dipoles along the common mode
The idea behind the experiment
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currentnanofiber
α =γ1Dγ0
Coupling Enhancement
Weuseuntrappedatoms!
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Measuring the Radiative Lifetime
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Measuring the Radiative Lifetime
1 mm
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F=1F=2
F’=2F’=3
F’=1F’=0
De-pump Re-pump Probe
De-pump
Probe
Re-pump
Preparing the Atoms
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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
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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)
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-4
-3
-2
-1
0
Log 10
cou
nt r
ate
0 5 10 15 20 25 30t/τ
0
Two distinct lifetimes
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-4
-3
-2
-1
0
Log 10
cou
nt r
ate
0 5 10 15 20 25 30t/τ
0
Two distinct lifetimes
τ ≈ 7.7τ 0
τ ≈ 0.9τ 0
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Two distinct lifetimes
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
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Decay time vs detunning
No radiation trapping for long lifetime
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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
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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
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-4
-3
-2
-1
0
Log 10
cou
nt r
ate
0 5 10 15 20 25 30t/τ
0
Two distinct lifetimes
τ ≈ 7.7τ 0
τ ≈ 0.9τ 0
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N dependence
γsup = γ rad + Nγ1D
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N dependence
γsup = γ rad + Nγ1D
Superradiance depends on the atom number!
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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 )
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The slope (0.02) is smaller than γ1D (0.10) because it is an average over different realizations, non all of them superradiant.
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Sub-radiance???
γsup = γ rad + Nγ1D
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Infinite-range subradiance is limited!
Subradiance???
γ sub = γ rad −γ1D
γsup = γ rad + Nγ1D
γ radγ1D
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-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!
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Understanding the Signal
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Understanding the Signal
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Polarization dependent signal
VerDcallypolarizedprobe Horizontallypolarizedprobe
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Polarization dependent signal
Vertically polarized probe Horizontally polarized probe
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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
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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
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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
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Fitting the Simulation
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Long distance modification of the atomic radiation
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Long distance modification of the atomic radiation
We have atomic densities low enough to observe mostly infinite-range interactions
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nanofiber
Left MOT
Splitting the MOT in two
Right MOT
≈ 400λ
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Right MOT
Left MOT
Both MOTs
Evidence of infinite-range interactions
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Observations: About one in 50 of the decays is super-radiant. Quantitative agreement with simulations.
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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.
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Thanks!
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