transient enhancement of the nonlinear atom-photon coupling via recoil-induced resonances:
DESCRIPTION
Transient enhancement of the nonlinear atom-photon coupling via recoil-induced resonances:. FIP. Joel A. Greenberg and Daniel. J. Gauthier Duke University 5/22/2009. Cavity-less Rayleigh Superfluorescence in a Thermal Gas. Superfluorescence (SF). Pump. W. N. L. W 2 /L l~1. - PowerPoint PPT PresentationTRANSCRIPT
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
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
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)
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
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)
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 /
SF MechanismSF Mechanism
What is the mechanism responsible for SF?
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
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
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
• 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
• Study dependence of Ppeak and D on N
• Look at competition between vibrational Raman and Rayleigh SF
Future WorkFuture Work
700 500 300
BeatnoteBeatnote
(kHz)
Look at beatnote between probe beam and SF light as probe frequency is scanned
Pow
er (
F)
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
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
Weak probeWeak probe
Probe (p=+)
Pumps ()
Forward
Backward
250 0 2500
2
4
6FWM Above Thresh
Below thresh
(kHz)
Weak probeWeak probe
Probe (p=+)
Pumps ()
Forward
Backward
Backward
400 200 0 200 400 400 200 0 200 400
Forward
(kHz) (kHz)
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
Lin || LinLin || Lin
100 200 300
Pow
er
time (s)
Pumps ()
Forward
Backward
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
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
ConclusionsConclusionsRayleigh backscattering
Recoil-mediated FWM
250 0 250
1
2
250 0 2500
1
2
(kHz)
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
Superfluorescence (SF)Superfluorescence (SF)
L,N
Pump
gL1
Spontaneous Emission
Amplified Spontaneous Emission (ASE)
Superfluorescence (SF)
SF Thresh
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
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
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
Observation of Cavity-less Rayleigh Superfluorescence in a
Thermal Gas
Joel A. Greenberg and Daniel. J. Gauthier
Duke University
5/22/2009
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)
• Motivation
• Collective effects
• Self-organization
• Experimental results
• Conclusions/Future work
OutlineOutline