Transient enhancement of the nonlinear atom-photon coupling via recoil-induced resonances:
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Transcript of Transient enhancement of the nonlinear atom-photon coupling via recoil-induced resonances:
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Transient enhancement of the nonlinear atom-photon coupling via
recoil-induced resonances:
Joel A. Greenberg and Daniel. J. Gauthier
Duke University
5/22/2009
Cavity-less Rayleigh Superfluorescence in a Thermal Gas
FIP
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Superfluorescence (SF)Superfluorescence (SF)
L
Pump
Dicke, Phys. Rev. 93, 99 (1954); Bonifacio & Lugiato, Phys. Rev. A 11, 1507 (1975), Polder et al., Phys. Rev. A 19, 1192 (1979), Rehler & Eberly, Phys. Rev A 3, 1735 (1971)
WN
‘endfire’ modes
W2/L
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SF ThresholdSF Threshold
time
Pow
er
SFsp/N
sp
• Cooperative emission produces short, intense pulse of light
• PpeakN2
• Delay time (D) before pulse occurs
• Threshold density/ pump power
D
Ppeak
1
Spontaneous Emission
Amplified Spontaneous Emission (ASE)
Superfluorescence (SF)
SF Thresh
Cooperativity
Malcuit, M., PhD Dissertation (1987); Svelto, Principles of Lasers, Plenum (1982)
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New Regime: Thermal Free-space SFNew Regime: Thermal Free-space SF
10~
Pump (F)Cold atoms
Pump (B)
Detector (B)
Detector (F)- T=20 K
- L=3 cm, R=150 m - N~109 Rb atoms
- PF/B~4 mW - F2F’3=5
F=R2/L~1
NO CAVITY!NOT BEC!
≠ Slama et al. ≠ Inouye et al.
Inouye et al. Science 285, 571 (1999); Slama et al. PRL 98, 053603 (2007)
* Counterpropagating,
* Large gain path length2
collinear pump beams1
1) Wang et al. PRA 72, 043804; 2) Yoshikawa PRL 94, 083602
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Results - SFResults - SF
0 100 200 3000
1
2
3
t (s)
Pow
er (W
)
Forward
Backward
F/B PumpsMOT beams
• Light persists until N falls below threshold
• F/B temporal correlations
• ~1 photon/atom large fraction of atoms participate
on
off
Wang et al. PRA 72, 043804 (2005)
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0 1 2 3 401234
2 3 4255075
100
Dtime
Pow
erPpeak
PF/B (mW)
Pp
eak
(W
)
D (s
)
PF/B (mW)
2/1/
BFP
•Density/Pump power thresholds
•PpeakPF/B
• D (PF/B)-1/2
Results - SFResults - SF
Consistent with CARL superradiance*
*Piovella et al. Opt. Comm. 187, 165 (2001)
BFP /
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SF MechanismSF Mechanism
What is the mechanism responsible for SF?
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Probe
Pump (F)Cold atoms
Pump (B)Detector (B)
- T=20 K - L=3 cm, R=150 m- N~109 Rb atoms
- PF/B~4 mW - F2F’3=5
10~
Detector (F)
(p =+)
What is the mechanism responsible for SF?
SF MechanismSF Mechanism
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Probe SpectroscopyProbe Spectroscopy
0 100 200
Forward Detector
Backward Detector (FWM)
250 0 250
250 0 250 (kHz)
Rayleigh
SF signal
time (s)
Pro
be P
ower
P
robe
Pow
er
Rayleigh pump beam alignment
Raman pump beam alignment
SF
Pow
er
Raman
SF
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Probe SpectroscopyProbe Spectroscopy
0 100 200
Forward Detector
Backward Detector (FWM)
250 0 250
250 0 250 (kHz)
Rayleigh
SF signal
time (s)
Pro
be P
ower
P
robe
Pow
er
Rayleigh pump beam alignment
Raman pump beam alignment
SF
Pow
er
Raman
SFRayleigh scattering is critical
for observation of SF
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• Observe free-space superfluorescence in a cold, thermal gas
• Large F/B gain path length + pair of pump beams
• Spectroscopy and beatnote imply Rayleigh scattering as source of SF
• Temporal correlation between forward/backward radiation
ConclusionsConclusions
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• Study dependence of Ppeak and D on N
• Look at competition between vibrational Raman and Rayleigh SF
Future WorkFuture Work
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700 500 300
BeatnoteBeatnote
(kHz)
Look at beatnote between probe beam and SF light as probe frequency is scanned
Pow
er (
F)
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700 500 300
170 172 174 176
BeatnoteBeatnote
(kHz)
time (s)
1/f f~450kHz fSF~-50kHz
Look at beatnote between probe beam and SF light as probe frequency is scanned
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Weak probeWeak probe
Forward: Rayleigh backscattering Backward: Recoil-mediated FWM
250 0 250
1
2
250 0 2500
1
2
(kHz) (kHz)
Probe (p=+)
Pumps ()
I ou
t/Iin
I ou
t/Iin
Forward
Backward
Rayleigh Rayleigh
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Weak probeWeak probe
Probe (p=+)
Pumps ()
Forward
Backward
250 0 2500
2
4
6FWM Above Thresh
Below thresh
(kHz)
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Weak probeWeak probe
Probe (p=+)
Pumps ()
Forward
Backward
Backward
400 200 0 200 400 400 200 0 200 400
Forward
(kHz) (kHz)
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Coherence TimeCoherence Time
0 1 2 3 4 5 60.00.20.40.60.81.0
time
Pow
er
F/B Pumpson
off
off
1
PR
PR
off
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Lin || LinLin || Lin
100 200 300
Pow
er
time (s)
Pumps ()
Forward
Backward
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Dtime
Pow
erPpeak
Pp
eak
(W
)Results - SFResults - SF
*Piovella et al. Opt. Comm. 187, 165 (2001)
0 5 10 15 20 250.000.050.100.150.20
OD N
)(NExp2)( tNN
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CARL RegimesCARL Regimes
Slama Dissertation (2007)
Quantum CARL
Ultr
acol
d A
tom
s/B
EC
Good Cavity: <r Bad Cavity: >r
Quantum:
r>G
Semiclassical:
r<G
In resonator Free space
MIT (2003)
MIT (1999)
Tub (2006)
Tub (2003)
Tub (2006)
The
rmal
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ConclusionsConclusionsRayleigh backscattering
Recoil-mediated FWM
250 0 250
1
2
250 0 2500
1
2
(kHz)
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Superfluorescence (SF)Superfluorescence (SF)
L,N
Pump
Pow
er
SFsp/N
sp
D
Ppeak • Cooperative emission produces short, intense pulse of light
• Emission occurs along ‘endfire’ modes
• PpeakN2
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Superfluorescence (SF)Superfluorescence (SF)
L,N
Pump
gL1
Spontaneous Emission
Amplified Spontaneous Emission (ASE)
Superfluorescence (SF)
SF Thresh
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Weak probeWeak probe
Forward: Rayleigh backscattering Backward: Recoil-mediated FWM
250 0 250
1
2
250 0 2500
1
2
(kHz) (kHz)
Probe (p=+)
Pumps ()
I ou
t/Iin
I ou
t/Iin
Forward
Backward
Rayleigh Rayleigh
RNg 2
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Probe SpectroscopyProbe Spectroscopy
0 100 200
Forward Detector Backward Detector (FWM)
250 0 250 250 0 250 (kHz) (kHz)
Rayleigh
SF signal
time (s)
Pro
be P
ower
Pro
be P
ower
Rayleigh pump beam alignment
Raman pump beam alignment
SF
Pow
erRaman
SF
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Forward Detector Backward Detector (FWM)
Probe SpectroscopyProbe Spectroscopy
0 100 200
250 0 250 250 0 250 (kHz) (kHz)
Rayleigh
SF signal
time (s)
Pro
be P
ower
Pro
be P
ower
Rayleigh pump beam alignment
Raman pump beam alignment
SF
Pow
er
Rayleigh scattering is critical for observation of SF
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Observation of Cavity-less Rayleigh Superfluorescence in a
Thermal Gas
Joel A. Greenberg and Daniel. J. Gauthier
Duke University
5/22/2009
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Our SetupOur Setup
10~
Pump (F)Cold atoms
Pump (B)Detector (B)
Detector (F)- T=20 K - L=3 cm, R=150 m- N~109 Rb atoms
- PF/B~4 mW - F2F’3=5
- No cavity- Thermal atoms- Counterprop. pumps
Inouye et al. Science 285, 571 (1999); Slama et al. PRL 98, 053603 (2007)
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• Motivation
• Collective effects
• Self-organization
• Experimental results
• Conclusions/Future work
OutlineOutline