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TRANSCRIPT
http://www.umich.edu/aehardt
Developing a Portable Optical
Frequency Standard
with Atomic Mercury
K.R. Moore†, E.A. Alden*, A.E. Leanhardt* Leanhardt Lab
†Applied Physics Program, University of Michigan
*Physics Department, University of Michigan
June 6, 2012 DAMOP XLIII, Anaheim CA
http://www.umich.edu/aehardt
Overview
June 6, 2012 DAMOP XLIII, Anaheim CA
• Hg frequency standard for a hot optical clock
• Limiting broadening mechanism contributing
to fractional frequency uncertainty
• Schemes for detecting population in clock state
http://www.umich.edu/aehardt
Frequency Standards
June 6, 2012 DAMOP XLIII, Anaheim CA
Δν: Linewidth of system
ν: Frequency of sampling probe
T: Duty cycle of experiment
τ: Total experiment time
N: Sample size per duty cycle
•* denotes theorized values not experimentally realized
•References available
• Fractional frequency uncertainty:
http://www.umich.edu/aehardt
Frequency Standard with Atomic Hg
June 6, 2012 DAMOP XLIII, Anaheim CA
[1] Calculated, natural abundance: A.P.
Mishra and T.K. Balasubramamian.
JQSRT 69, 769 - 780 (2001)
τ =5.78s [1]
3P0
3P1
1S0 531nm
531nm Δν: Linewidth of system
ν: Frequency of sampling probe
T: Duty cycle of experiment
τ: Total experiment time
N: Sample size per duty cycle
• Fractional frequency uncertainty:
http://www.umich.edu/aehardt
Δν: Linewidth of system
ν: Frequency of sampling probe
T: Duty cycle of experiment
τ: Total experiment time
N: Sample size per duty cycle
• Fractional frequency uncertainty:
Frequency Standard with Atomic Hg
June 6, 2012 DAMOP XLIII, Anaheim CA
[1] Calculated, natural abundance: A.P.
Mishra and T.K. Balasubramamian.
JQSRT 69, 769 - 780 (2001)
τ =5.78s [1]
3P0
3P1
1S0 531nm
531nm
http://www.umich.edu/aehardt
Δν: Linewidth of system
ν: Frequency of sampling probe
T: Duty cycle of experiment
τ: Total experiment time
N: Sample size per duty cycle
• Fractional frequency uncertainty:
Frequency Standard with Atomic Hg
June 6, 2012 DAMOP XLIII, Anaheim CA
Hg atoms
Laser
E
E
• Eliminate first-order Doppler
broadening of the linewidth
http://www.umich.edu/aehardt
• Limitations due to portability:
Broadening: Collisions
Broadening: Laser power amplification
June 6, 2012 DAMOP XLIII, Anaheim CA
System Portability
• Portability:
Vapor cell atomic source:
Solid-state compact laser:
60. Col kHz
?. Las
Cell temperature: 60ºC
http://www.umich.edu/aehardt
Laser Characterization
Seed Laser:
20 mW
1062 nm
Δν = 914 Hz*
Amplifier:
50 W
1062 nm
Δν ≤ ?
June 6, 2012 DAMOP XLIII, Anaheim CA
*measured by
Orbits Lightwave
SHG:
6 W
531 nm
Δν2 212 input
http://www.umich.edu/aehardt
Laser Characterization
Seed Laser:
20 mW
1062 nm
Δν = 914 Hz*
Amplifier:
50 W
1062 nm
Δν ≤ ?
June 6, 2012 DAMOP XLIII, Anaheim CA
*measured by
Orbitz Lightwave
SHG:
6 W
531 nm
Δν2 212 input
http://www.umich.edu/aehardt
Laser Characterization
From Seed
Beat Note:
1MHz
• Shifting the laser frequency in a Mach-Zender interferometer results in a
beat note centered at a down-converted frequency.
June 6, 2012 DAMOP XLIII, Anaheim CA
AOM
AOM
http://www.umich.edu/aehardt
Laser Characterization
From Seed
June 6, 2012 DAMOP XLIII, Anaheim CA
AOM
AOM
• Shifting the laser frequency in a Mach-Zender interferometer results in a
beat note centered at a down-converted frequency.
http://www.umich.edu/aehardt
Laser Characterization
June 6, 2012 DAMOP XLIII, Anaheim CA
Hz
His
t. C
ou
nts
Linewidth:
12.1±6.1Hz
• A delay line is required to verify the actual linewidth.
• The relative broadening between the seed-seed beat note and the seed-
amplified beat note can be measured to some limit.
• Beat note, example data set:
Beat
Seed
with
Seed:
http://www.umich.edu/aehardt
Laser Characterization
From Seed
Beat Note:
1MHz
June 6, 2012 DAMOP XLIII, Anaheim CA
AOM
AOM
• In place of the amplifier, external noise is artificially applied to one arm
of the interferometer.
http://www.umich.edu/aehardt
Laser Characterization
From Seed
Beat Note:
1MHz Artificial
Noise
• In place of the amplifier, external noise is artificially applied to one arm
of the interferometer.
June 6, 2012 DAMOP XLIII, Anaheim CA
AOM
AOM
http://www.umich.edu/aehardt
kHz
Am
pl.
(a.
u.)
kHz
Am
pl.
(a.
u.)
Laser Characterization
June 6, 2012 DAMOP XLIII, Anaheim CA
Linewidth:
12.1±6.1Hz
Beat
Seed
with
Artificial
Noise (50mV):
• Beat note, example data set:
Beat
Seed
with
Seed:
Linewidth:
2.7±0.5kHz
http://www.umich.edu/aehardt
Laser Characterization
From Seed
Beat Note:
1MHz Artificial
Noise
June 6, 2012 DAMOP XLIII, Anaheim CA
AOM
AOM
• Shifting the laser frequency in a Mach-Zender interferometer results in a
beat note centered at a down-converted frequency.
http://www.umich.edu/aehardt
Laser Characterization
From Seed
Beat Note:
1MHz
• Shifting the laser frequency in a Mach-Zender interferometer results in a
beat note centered at a down-converted frequency.
June 6, 2012 DAMOP XLIII, Anaheim CA
AOM
AOM
http://www.umich.edu/aehardt
Laser Characterization
From Seed
Beat Note:
1MHz
AOM
AOM
Amplifier
June 6, 2012 DAMOP XLIII, Anaheim CA
• Shifting the laser frequency in a Mach-Zender interferometer results in a
beat note centered at a down-converted frequency.
http://www.umich.edu/aehardt
kHz
Am
pl.
(a.
u.)
kHz
Am
pl.
(a.
u.)
Laser Characterization
June 6, 2012 DAMOP XLIII, Anaheim CA
Beat
Seed
with
Amplified
Light (14.2W):
• Beat note, example data set:
Beat
Seed
with
Seed:
Linewidth:
12.1±6.1Hz
Linewidth:
7.2±3.6Hz
http://www.umich.edu/aehardt
Laser Characterization
June 6, 2012 DAMOP XLIII, Anaheim CA
• After replacing the amplifier in the system, measurements show no
systematic change in the linewidth of the beat note.
ΔL
inew
idth
[H
z]
IR Power [W]
• Increasing amplifier power:
http://www.umich.edu/aehardt June 6, 2012 DAMOP XLIII, Anaheim CA
Broadening Mechanisms
• Theorized values for other broadening mechanisms:
Cell temperature: 60ºC | Spot size: 500 μm | Green power: 6 W
http://www.umich.edu/aehardt June 6, 2012 DAMOP XLIII, Anaheim CA
Broadening Mechanisms
• Theorized values for other broadening mechanisms:
Cell temperature: 60ºC | Spot size: 500 μm | Green power: 6 W
http://www.umich.edu/aehardt June 6, 2012 DAMOP XLIII, Anaheim CA
Broadening Mechanisms
• Theorized values for other broadening mechanisms:
Cell temperature: 60ºC | Spot size: 500 μm | Green power: 6 W
http://www.umich.edu/aehardt June 6, 2012 DAMOP XLIII, Anaheim CA
Broadening Mechanisms
• Theorized values for other broadening mechanisms:
Cell temperature: 60ºC | Spot size: 500 μm | Green power: 6 W
Duty Cycle: 1/T < 0.1 Hz | Number of interacting atoms: N ≈ 6×1012
http://www.umich.edu/aehardt June 6, 2012 DAMOP XLIII, Anaheim CA
Broadening Mechanisms
• Theorized values for other broadening mechanisms:
Cell temperature: 60ºC | Spot size: 500 μm | Green power: 6 W
Duty Cycle: 1/T < 0.1 Hz | Number of interacting atoms: N ≈ 6×1012
2/11610
http://www.umich.edu/aehardt
Proof-of-Principle Outlook
• Detect population in
the 3P0 level using:
• Known cascade with
NH3 buffer gas[1]
• Excite to the 3S1 level
with 405nm, detect
radiative decay[2]
June 6, 2012 DAMOP XLIII, Anaheim CA
[1] C.G. Freeman, M.J. McEwan, R.F.C. Claridge and L.F. Phillips.
Trans. Faraday Soc., 1971,67, 2004-2008
[2] E. C. Benck, J. E. Lawler and J. T. Dakin. JOSAB 6, 11 (1989)
63P0
61S0
531nm
531nm
63P2
61P1
63P1
73S1
405nm
http://www.umich.edu/aehardt
Summary
• Compact, solid-state set-up for an optical clock
• Limited by collisional broadening, which
could lead to a fractional frequency stability of
σν ≈ 10-16 ×√τ.
• Outlook for detecting population
June 6, 2012 DAMOP XLIII, Anaheim CA
http://www.umich.edu/aehardt
Acknowledgements
June 6, 2012 DAMOP XLIII, Anaheim CA
Aaron
Leanhardt
Skyler
Degenkolb Yisa
Rumala
Jeongwon
Lee Emily
Alden Kaitlin
Moore
• Funding:
DARPA/ARO
• Dept. of Physics,
University of
Michigan
• Applied Physics
Program, Univ-
ersity of Michigan
Tim
Chupp
http://www.umich.edu/aehardt
Standards References
June 6, 2012 DAMOP XLIII, Anaheim CA
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
D. McKenna, C. Tanner. Progress toward a two-photon optical atomic clock in neutral
silver. Abstract submitted for the DAMOP12 Meeting of APS (K1.00140), January 2012.