Population Transfer Resonance: A new Three-Photon Resonance for Small Scale Atomic Clocks Ido...
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Transcript of Population Transfer Resonance: A new Three-Photon Resonance for Small Scale Atomic Clocks Ido...
Population Transfer Resonance: A new Three-Photon Resonance for Small Scale Atomic Clocks
Ido Ben-Aroya, Gadi Eisenstein
EE Department, Technion, Haifa, Israel.
Technion
FRISNO-11, Aussois, France, Mar. 2011
FRISNO-11 Ido B – Technion, Israel. 2
The Synchronous WorldThe Quartz Crystal Oscillators (1920stoday)
NIST (NBS) Frequency Standard by Bell labs, 1929. 4 x 100 KHz crystal oscillators.
stability: 10-7 Source: NIST
•Resonance frequency shifted due to aging
•No two crystals with the same frequency.
FRISNO-11 Ido B – Technion, Israel. 3
Frequency/Time Standard
• An oscillator with poor long-term stability (hours to
years) is locked on a narrow filter around a fixed frequency improved long-term stability.
Local Oscillator (Quartz Crystal)
f0
Δf
•High contrast
•Narrow width
•Fixed f0•Stable during feedback
Principle of Operation
FRISNO-11 Ido B – Technion, Israel. 4
Types of Reliable Frequency Standards
Source: Symmetricom
CSAC:
•Small dimension
•Low power consumption
2’’
FRISNO-11 Ido B – Technion, Israel. 5
CPT based CSAC
• CPT – Two photon coherent process yielding narrow resonances with low contrast
• Clocks require complex locking schemes – Multi field FM spectroscopy
• Large contrast resonances eliminate many of the locking problems
-600 -400 -200 0 200 400 6000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
CPT resonance matching around 3 417.352 499MHz (span 1.5KHz). Resonance width=186Hz
f (around 3 417.352 499MHz ; span 1.2KHz) [Hz]
Am
p [a
rb.
units
]
raw dataLorentzian
f=186Hz
• D2 transition (780nm).
• Resonance width – 186Hz
• Contrast – 0.5% - 1%.
FRISNO-11 Ido B – Technion, Israel. 6
Types of Atomic Resonances
• Important characteristics: width and height (or contrast)
EIA-type: Population Transfer Resonance (PTR)
Inspired by Zibrov and Walsworth group “N-resonance” demonstration.
Electromagnetically Induced Transparency (EIT) type:
Electromagnetically Induced Absorption (EIA) type:
FRISNO-11 Ido B – Technion, Israel. 7
Population Transfer Resonance
2g
1g
e
fhfs
fhfs/2
1 2 3
•Three-level -system interacts with three phase-locked fields in an N-type configuration scheme.
12
3
FRISNO-11 Ido B – Technion, Israel. 8
Population Transfer Resonance
2g
1g
e
fhfs
fhfs/2
1 2 3
• The probe 3, is tuned on resonance and therefore is absorbed by the medium.
• 1 and 2 are highly one-photon detuned and sweep near the zero two-photon Raman detuning.
FRISNO-11 Ido B – Technion, Israel. 9
Population Transfer Resonance
2g
1g
e
fhfs
fhfs/2
1 2 3
• 3 optically pumps the medium from |g2> to |g1>.
• The two-photon process induced by 1 and 2 transfers the population back from |g1> to |g2> …
FRISNO-11 Ido B – Technion, Israel. 10
Population Transfer Resonance
2g
1g
e
fhfs
fhfs/2
1 2 3
The absorption of 3 is enhanced due to the repopulation of |g2>
Electromagnetically Induced Absorption (EIA)-type resonance.
FRISNO-11 Ido B – Technion, Israel. 11
The Spectral Constellation87Rb : F=2->F’ F=1->F’
32 112 ~ hfsf
• The interacting frequency components originate from a laser which is locked to the 87Rb D2 transition (|F=2>|F’=2>) and modulated by half the 87Rb hyperfine splitting frequency (fhfs/2=3.417 GHz).
2g
1g
e
fhfs
fhfs/2
1 2 3
FRISNO-11 Ido B – Technion, Israel. 12
The Setup
w
vapor cell in -metal
F-P
Spectrum Analyzer
/42 F-P filters
Detector ND Laser
PM and
filters
•3 main blocks: Source, Medium, and Detection formation.
•Parameters: Modulation frequency (12), Total intensity (I), and Carrier to 1st side lobe intensity ratio (C1L).
32 112
32 1
FRISNO-11 Ido B – Technion, Israel. 13
First Observation
• The probe (3) intensity (normalized) is measured versus PM frequency sweeping near 3 417 345 KHz for various C1L ratios. I=300 W.
Approx. 50 % contrast.
FRISNO-11 Ido B – Technion, Israel. 14
First Observation
• EIA-type resonance for the probe (3) and 1.• EIT-type resonance for 2.
12
3
32 112
3
2
1
FRISNO-11 Ido B – Technion, Israel. 15
The Model
2g
1g
e
fhfs
fhfs/2
1 2 3
Probing 2-ph process: The Population Coupling model
2g
1g
e
p
Γ1→2
2g
1g
eΔ
1 2
Γ2→1
B: Two highly one-photon detuned fields interacting with a three-level -system with a |g2>|g1> coupling channel.
A: One, “on resonance” field interacting with a three-level -system with a |g1>|g2> coupling channel.
Two processes coupled by the population of their states
FRISNO-11 Ido B – Technion, Israel. 16
The Model (phase II)
• The population coupling model is insufficient in describing the obtained resonance for moderate probe intensities.
• The coupling model neglects the existence of each process field(s) in the other process.
• The “missing information”: the coherence in both processes.
2g
1g
e
fhfs
fhfs/2
1 2 3
The Coupling of Coherence
2g
1g
e
p
Γ1→2212g
1g
eΔ
1 2
Γ2→1
2g eProcess BProcess A
FRISNO-11 Ido B – Technion, Israel. 17
• The population of |g2> is given by a ratio between two polynomial terms of symmetric (Lorentzian) and anti-symmetric (“dispersion-like”) functions of the modulation frequency ().
• The approximated anti-symmetric and symmetric functions:
2g
1g
e
fhfs
fhfs/2
1 2 3
2g
1g
e
p
Γ1→2212g
1g
eΔ
1 2
Γ2→1
2g e
Process BProcess A
Symmetric
Anti-
Symmetric Fundamental Width:
probe
atom
2-ph
The Model
FRISNO-11 Ido B – Technion, Israel. 18
The Model
• The absorption of the probe, under several assumptions, is an almost symmetric function of the modulation frequency:– Width (HWHM):
– Height:
– Where s is the saturation parameter:
2g
1g
e
fhfs
fhfs/2
1 2 3
2g
1g
e
p
Γ1→2212g
1g
eΔ
1 2
Γ2→1
2g e
Process BProcess A
FRISNO-11 Ido B – Technion, Israel. 19
The Model2g
1g
e
fhfs
fhfs/2
1 2 3
Results 2g
1g
e
p
Γ1→2212g
1g
eΔ
1 2
Γ2→1
2g e
Process BProcess A
Width (HWHM)
Height
FRISNO-11 Ido B – Technion, Israel. 20
Model versus MeasurementsModel Meas.
FRISNO-11 Ido B – Technion, Israel. 21
The Role of Temperature
• Higher temperatures more atoms and higher velocities.
• Assumption: a change in temperature does not effect 12.
• 1 and 2 are not absorbed by the medium (due to the one-photon detuning).
• 3 obeys Beer-Lambert law:
namely, the probe (and only the probe) is absorbed by atoms in the medium which do not participate in the three-photon process.
Vapor Temperature, Beer Law, and PTR
FRISNO-11 Ido B – Technion, Israel. 22
The Role of Temperature
• At low intensities of the probe, the EIA effect is negligible.
• At higher temperatures the effect is shifted towards higher C1Ls.
• ‘Stronger’ resonances are expected at higher temperatures.
Vapor Temperature, Beer Law, and PTR
Beer-Lambert :
FRISNO-11 Ido B – Technion, Israel. 23
The Role of TemperatureModel Results
No EIA
Shift in the effect
Higher resonanc
es
FRISNO-11 Ido B – Technion, Israel. 24
The Role of TemperatureExperimental Observations
No EIA
Higher resonanc
es
Shift in the effect
FRISNO-11 Ido B – Technion, Israel. 25
Back to the Experimental Setup
32 1
32 1
32 15 4
FRISNO-11 Ido B – Technion, Israel. 26
PM
w
vapor cell in -metal
F-P filter
F-P
Spectrum Analyzer
ND/4
m
F-P filter
Detector
ECDL
PSBP
w
Locking Scheme
m
Back to the Experimental Setup
32 15 4
32 1
No Filters Before Cell
FRISNO-11 Ido B – Technion, Israel. 27
Five Fields87Rb : F=2->F’ F=1->F’
32 112 ~ hfsf
2g
1g
e
fhfs
fhfs/2
1 2 3
87Rb : F=2->F’ F=1->F’
32 1
1245
145 22
12
3
2g
1g
e
fhfs
fhfs/2
1 2 3fhfs/2
54
FRISNO-11 Ido B – Technion, Israel. 28
Experimental ResultsFive Spectral Lines
-75 -50 -25 25 50 750.875
1
1.075
[KHz]
I (n
orm
)
8.0%;100.0%
12.0%;148.8%
16.2%;200.0%
20.2%;251.2%
24.4%;300.0%
C1L ; C2L
EIT
EIA
Anti-Symmetric Resonance
FRISNO-11 Ido B – Technion, Israel. 29
The Anti-Symmetric Resonance
• The Local Oscillator should be stable during feedback.
A Novel Scheme for Atomic Clocks?
ATOM RES.
LO
• Employing symmetric resonances requires peak detection which delays the feedback
• Anti-symmetric resonances provides an almost instantaneous feedback, therefore other, less stable oscillators can be used– Thin Film Resonators
FRISNO-11 Ido B – Technion, Israel. 30
Summary
• A new type of EIA resonance was introduced.– Resonant population transfer in a three-level
-system induced by three electromagnetic fields.
• A large contrast (~50%) was observed.
• A model describing the interaction was introduced.
• The role of vapor temperature was discussed.
• A first glance over the interaction of five fields with the same medium.– A new scheme for atomic clocks?
FRISNO-11 Ido B – Technion, Israel. 31
Acknowledgement
• This work is partially supported by the Technion Micro Satellite Program.
• Ramon fellowship of the Israeli ministry of science.
Thank you