Defining and Measuring Optical Frequencies · 2020-02-05 · Metrology, the Mother of Science...
Transcript of Defining and Measuring Optical Frequencies · 2020-02-05 · Metrology, the Mother of Science...
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Test slide
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John L. Hall
JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado at Boulder
Optical Atomic ClocksDefining and measuring (Optical) Frequencies
then, now and next
Jun Ye
http://HallStableLasers.comhttp://Jilawww.Colorado.edu
NI$TN$F
NA$A ONR
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Hall_Labs 2000
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Today’s Symposium: - Fundamental Physics – looking insideKaon Lifetimes Local Lorentz Invariance? Are the Numbers of Physics
time-dependent?Dark Matter Dark Energy?
How to make progress?
a. Visit the Tools store (specializing in laser and electro-optics for all your needs)b. Be sure you can get more resolution with whatever tools you buy! ~N3/2
New Comb Toolsfor Speedy & AccurateFrequency/PhaseMeasurement
A Great Highway!With 15+ digits, youmight find somethinginteresting …
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Mechanical clockworks
Verge and Foliot escapement
Fusee
Pendulum clock
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Mechanical clockworks
Anchor escapementSpiral balance spring
1675, Huygens, Netherlands
1772, John Harrison, clock H-51 s per 3 days (~4 x 10-6 )~1670, in England
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Watch, 2002.Mechanical clock, 1657.
Water clock &Sandglass.Sundial, 1st or 2nd
century A.D.
Quartz clock Atomic micro clock
Atomic hydrogen maser clock, early 1960s.
Grandfather clock
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Atomic Time from NIST, by radio
WWVB 60 kHzFt. Collins Colorado
“Sweet Spot”Better than needed
Just-right TechCost Effective
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What is a clock?
Stable Oscillator
Counter
Caveman’sMarks on thecave walls Electronic
zero-crossingCounter
NIST-F1BNM - SYRTE
laser
fs comb
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CH4 – stabilizedHeNe 3.39µm Laser
3.39µm tunable Laserlocked to 30 m Cavity
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Saturated Absorptionin Methane Gas
Line “Q” ~109
Reproducibility ~10-11
Instability < 10-13
prl 1969
“Working with the Methane-stabilized HeNe Laser at 3392 nm (3.39 µm)”
Jan Hall and Dick Barger ~ 1972
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τtr = w0 / v
∆ν ≅ 88 kHz •mm/ w0
Transit-time Increase, with Big Beams
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Pushing up the Resolution ~ 19731 kHz HWHM ~ 10-5 *Doppler Width
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Hall, Bordé, Ueharaprl 37 1339 (1976)
Recoil-induced splitting of hfs Lines (CH4)
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A New Wavelength Standard? !!!
HeNe fringesAt 3.39 µm
Krypton fringesAt 605.7 nm (1960)
4 x10-9 in 300 s !
Frequency Scan
R. L. Barger and JLH’71 ; APL 22, 196 (1973)
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BIPM’s Kg and Metre ProtoTypesMetre bar replaced in 1960 by light-wave definition – Krypton 605.7 nm line (Isotope 86)
First optical fringe measurement by A. A. Michelson 1887 Nobel Prize 1907
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Metrology, the Mother of ScienceToday’s Symposium features Length and Time/Frequency
Length – Depends on:Inter-atomic distances,
E & M/ Quantum Mechanics
Ell, Braunschweig ~1600Metre Bar, Paris ~1875 Cadmium Lamp A.A.Michelson 1887Nobel Prize A.A.M. ±4 x10-7 1907Krypton Lamp ±4 x10-9 1960Methane-Stab. Laser ±1 x10-11 1972c adopted constant 0 1983
DayMean Solar Day 1875Tropical Astronomical Year 1960Cesium Second 1967Cs Fountain Clock ±1 x10-15 ~2000Hg+ -stabilized Laser ±1 x10-15 2004
Frequency – Depends on:
Internal electronic energy differencesE & M/ Quantum Mechanics
Fine-Structure Constant
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Measuring Optical Frequencies
Frequency Starting Point: 9, 192, 631, 770 cycles per second
Target Frequency of Mercury Ion: 1 064 721 609 899 143 cps
Frequency Ratio Needed: 115 823.372 081 …
A ratio of 115 Thousand !
How can we ever do this?
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Here’s the first Government PLAN
x7 x2 x2 x2 x2 x2 x2 x2 x2 x2 x2 x2 x2 x2 x2
1 electronic + 14 Laser stages
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Frequency spectrum in optical frequency synthesis
LogFrequency(Hz)
107
1010
1011
1012
1013
1014
1015
Crystal oscillator
Cs
HCOOHHCN
CH3OH
H2O
CO2OsO4
CH4
VisibleMolecularovertones
Rb, CsI2Ca
H, Hg+
Lasers
Microwaveoscillators,Klystrons,etc.
MIM orSchottkydiode
W-Siµwavediode
BWO
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The First NBS Optical Frequency Chain
NBS (NIST): measurement of speed of light, 1972
J. Wells
J. L. Hall & J. Ye, “NIST 100th birthday”, Optics & Photonics News 12, 44, Feb. 2001
K. Evenson
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c = ν λThe NBS Speed of Light Program:
ν =88 376 181 627. kHz± 50.
Evenson’s ν TeamK.M.E., J.S. Wells, F.R. PetersenB.L.Danielson, & G.W. DayAnd D. A. Jennings
λ =3 392.231 390 nm± .000 01
JILA λ TeamR. L.Barger & J. L. Hall
c = 299, 792, 457.4 m/s Our Finest Product !
PRL 29 1346 (1972)
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“The Metre is the length of the path travelled by light (in vacuum) in
1/299 792 458 of a second”
ie., c = 299 792 458 m/s, exactlyCGPM 1983
1983 Metre Re-Definition & Demotion
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Meanwhile, on Hwy 50, W of Port Allen, Kauai (Hawaii)
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Molecular Frequency Standards ~1997
• HeNe Laser w CH4 Absorber 3.39 µm• HeNe vis Laser w I2 Absorber ~5 vis λ’s• CO2 Laser w CO2 Absorber 10.6 µm• CO2 Laser w OsO4 Absorber 10.6 µm• Ar+ Laser w I2 Absorber 514 nm• Nd:YAG Laser w I2 Absorber 1064 nm• Nd:YAG Laser w C2HD Abs. 1064 nm• Yb:YAG Laser w C2H2 Abs. 1030 nm• Diode Lasers w C2H2 Abs. 1550 nm
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Venya Chebotayev &Ken Evenson
“How are we going to measure thoseoptical frequencies?”
Lindy, Vera, Ken, & Venya
Celebrating the new Hall_Labs, April 1988
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Frequency (THz)
CH4
Rb/2C2H2
I2/2C2HD Rb Ca HeNe I2Hg+
0 88 192.6 266.2 281.6 385.3 456 473.6 563
λ (nm) 3390 1556 11261064
778 657633
532
617
486
H
f(λ=632 nm) = f(λ=633 nm) + 660 GHz
f(λ=778 nm) + f(λ=532 nm) = 2 x f(λ=632 nm)
= 66 x 10 GHz (µ-wave/optical comb)
Kourogi’s 1994 Comb!
The JILA f(λ=532 nm) frequency measurement schemeIEEE Trans. Instrum & Meas. 48 583 (1999)
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Phase coherent distribution
Opticalfrequency
Q ~ 1014 – 1015 ω3
613 10~
ωω
Femtosecond Laser Comb106 :1 Reduction Gears
(not to scale!)
ω1
Radio Frequency
Q ~ 108 – 1011
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T. Hänsch (1978), V. P. Chebotayev (1977); Th. Udem,et al. PRL 82, 3568 (1999).
Measuring Spectral δ-functions with Temporal δ-functions?!
Frequency (THz)
CH4
Rb/2C2H2
I2/2C2HD Rb Ca HeNe I2Hg+
0 88 192.6 266.2 281.6 385.3 456 473.6 563
λ (nm) 3390 1556 11261064
778 657633
532
617
486
H
Timeτr.t=2L/vg
Frequency∆=1/ τr.t.
F.T.
•Periodicity in Time = Periodicity in Frequencyknown freq.
f0 unknown freq.f0+n ∆
1997
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The First Comb RF-Optical Link
4f –3.5 f = n frep
So: f = 2 n frep
“Phase Coherent Vacuum-Ultraviolet to Radio Frequency Comparisonwith a Mode-Locked Laser,” PRL 84 3232 (2000) 10 April 2000J. Reichert, M. Niering, R. Holzwarth, M. Weitz, Th. Udem, and T. W. Hänsch
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courtesy of Jinendra Ranka
Honeycomb Microstructure Optical Fiber CLEO,May, 1999
Dawn of a new Epoch !
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Seriously- nonlinear optics (O(20))
Lucent Technologies
R. Windeler J.K Ranka, R. S. Windeler, A. Stenz, Opt. Lett. 25, 25 (Jan. 2000)
Microstructured fiberdispersion zero at ~800 nmpulses do not spreadcontinuum generation via self-phase modulation
-70
-60
-50
-40
-30
Det
ecte
d P
ower
(dB
m)
12001000800600400Wavelength (nm)
Pre-fiber(Ti:Sapph)
After fiber
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Group vs. Phase in Modelocked Lasers
• Each pulse emitted by a modelocked laser has a distinct envelope-carrier phase– due to group-phase velocity differential inside
cavity
OutputCoupler
HighReflector
LaserCavity Free Space
Thanks: Steve Cundiff
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2πδ= ∆φ frep
I(f)
f
δ
0
frepI(f)
f
δ
0
frep
Time Domain Frequency Domain
•Frequency modes of the fs pulse are offset from fn=0=0 by δ
TimeDomain
Frequency Domain
2∆φ
t
E(t) ∆φ
1/ frepF.T.
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Self-referenced Optical Frequency Synthesizer
I(f)
f
fn=n∆-δ
δ
∆
f2n=2n∆-δx2 2fn=2n∆-2δ
0
δδ can be set at any fixed frequency:For example, δ = 0: fn = n ∆
Absolute control of carrier-pulse phase: extreme nonlinear optics, precision optical waveforms
Telle, Appl Phys B ‘99Jones, Science ‘00
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Output Coupler & Translating Piezo(Mode Position)
High Reflector& Tilting Piezo
(Mode Spacing)
PumpTi:Sapphire
Gain
Prism Pair
Phase-Controlled 10 fs Laser
β
Ln ∆∝ν
ν0
ν+1
ν+2
ν-1
∆L
β∝∆
ν0
ν+1
ν+2
ν-2
ν-1
∆∆
β
Th. Udem, et al, PRL 82, 3568 (1999).
∆L
Orthogonalizing control degrees of freedom
Laser: Kapteyn, Murnane, CundiffControl Ideas: Udem et. al., Hall, Ye
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20
18
16
14
12
10
f 1064
- C
IPM
Fre
quen
cy (k
Hz)
3020100Days
52504846
Mean Value: 17.17 kHzStandard Deviation: 590 Hz
122
25
20
15
10
5
0Mea
sure
d H
eNe
- A
ccep
ted
(kH
z)
86420Days
118117116115114
633 vs. 1064 633 vs. 532 Average of 90 microWatt data
After international comparison
-20
-15
-10
-5
0
5
10
Mea
sure
men
t - C
IPM
Val
ue (k
Hz)
A
B
C
DE
FG H
J
A: Nez, Opt Comm (1993); 633 and 3390 nm He-Ne'sB: Touahri, Opt Comm (1997); CO2/OsO4
C: Madej, email to Jan (1999); NRC ChainD,E: Reported values of LPTF systems (Madej, 1999)F,G,H Femtocomb measurement against self calibrated iodine (JILA)J Diode laser system, indirectly linked to femtocombe system (JILA)
Summary of available Rb 2-photon measurements at 778 nm
Data runs
60
40
20
0
Num
ber
-25 -20 -15 -10 -5 0 5 10 15Offset from recommended CIPM 1997 value (kHz)
mean= -3.7 kHzσ(1s)= 5 kHz
(a) (b)
(c) (d)
I2 – YAG 2H
I2-stabilized HeNe 633 nm
Three Absolute Frequency Measurements using the Self-Referencing Comb Method
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Self-Reference: JILA Experimental Setup
fAOM=7/8frep
Microstructure optical fiber
BBO
AOM
Filter Polarizer
Comb position locking servo
Visible (f2n)
Infrared (fn)
frep servo Rb atomic clock
2fn
Self-referenced continuum
15-fs Laser
f to 2f lock
frep
δ
Synthesizer
• Relative carrier-envelope phase: ∆φ = 2π = 2πfrep
m
16 δ
Science 288, 63528 May 2000D. J. Jones et al.
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Time Domain Cross-Correlator
Scan
GaAsPPhotodiode(nonlinear)
Vacuum
Matched mirror bounces
Interfere pulse i withpulse i + 2.L. Xu, et al., Opt. Lett. 21, 2008 (1996)
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Cross-Correlation
• Auto-correlation is always symmetric
• Cross-correlation fringes shift: pulse to pulse phase
• Fit to obtain envelope peak
• Extract carrier phase shift relative to envelope -20 -10 0 10 20
EnvelopeFit
Cross-Correlation
Delay (fs)S. Cundiff & D. J. Jones /JILA
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Systematic Phase Control
“Dial-in” pulse-to pulse phase
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90
2
4
6
8
10
experiment theory
∆φ
(rad
ians
)
δ/frep
Fiber phase noise issues,T. Fortier, PhD thesis ‘03
T. M. Fortier et al., SPIE 4271, p.183 (2001).
D. J. Jones, et al.Science 288 635 ’00
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Friendly - but Hot - Competition!
• “Phase Coherent Vacuum-Ultraviolet to Radio Frequency Comparison with a Mode-Locked Laser,” J. Reichert, M. Niering, R. Holzwarth, M. Weitz, Th. Udem, and T. W. Hänsch, PRL 84 3232 10 April 2000
• "Carrier-envelope phase control of femtosecond mode-locked lasers and direct optical frequency synthesis," D. J. Jones, S. A. Diddams, J. K. Ranka, A. Stentz, R. S. Windeler, J. L. Hall, and S. T. Cundiff, Science, vol. 288, pp. 635-639, 28 April 2000.
• “Direct Link between Microwave and Optical Frequencies,” Diddams et al., JILA; Ranka et al., Lucent; & Holzwarth et al. MPQ PRL 84 5102 29 May 2000
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Positive Interference
ScottDiddams(Boulder)
Thomas Udem
(Garching)
It makes:
Coherent Comb Lines
Great Fun & Progress
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fs Comb-Measured Optical Frequencies• Ca 657 nm Schnatz – PTB PRL 1 Jan ‘96• C2H2 1.5 µm Nakagawa - NRLM JOSA-B Dec ‘96• Sr+ 674 nm Bernard – NRC PRL 19 Apr ‘99• In+ 236 nm v. Zanthier - MPQ Opt.Comm. Aug’99• H 243 nm Reichert - MPQ PRL 10 Apr ’00• Rb 778 nm D. Jones - JILA Science 28 Apr 00• I2 532 nm Diddams - JILA PRL 29 May ’00• H 243 nm Niering - MPQ PRL 12 June ‘00• Yb+ 467 nm Roberts - NPL PRA 7 July ‘00 • In+ 236 nm v. Zanthier – MPQ Opt. Lett. 1 Dec.‘00 • Ca 657 nm Stenger – PTB PRA 17 Jan ‘01• Hg+ 282 nm Udem – NIST PRL 28 May ‘01• Ca 657 nm Udem – NIST PRL 28 May ‘01• Yb+ 435 nm Stenger – PTB Opt. Lett.15 Oct ‘01
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Advanced optical frequency standards- Bergquist, Hall, Hollberg, Ye
L. Hollberg & C. Oates
Single Hg+ ionJ. Bergquist
Trapped Sr
Line 1110 (R(56)32-0)a1
a15
857.957180 MHz
a3&a4
Portable Iodine system
Ye-group
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Nd:YAG/I2 Long term reproducibility
Measured frequency is confirmed by 375 MHz system/new fiber
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Prototype of an optical clock –fs Laser Stabilization by Phase Lock to Reference
frequency
Stabilized to 1f Stabilized to 2f
fs Laser
Stable Nd:YAG
Fiber
SHG
2ff
2ff
OrthorgonalizerTo tilting PZT
To translating PZT
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JILA I2 Optical Standard vs NIST Hg+ Reference
-10
-5
0
5
10
Frac
tiona
l ins
tabi
lity
(1E-
13)
6005004003002001000Time (s)
Optical measurement Microwave measurement (maser)
610-14
2
46
10-13
2
4
Alla
n D
evia
tion
12 3 4 5 6 7
102 3 4 5 6 7
1002 3
Averaging Time (s)
Remote Optical measurement Microwave measurement (maser) Local optical measurement
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-85
-80
-75
-70
-65
-60
-55
Bea
t Am
plitu
de (d
BV
)
56545250484644Fourier Frequency (kHz)
Fiber phase noise uncompensated
Fiber phase noise Compensated
FWHM:0.05 Hz
1 kHz
20 dB
Fiber Phase Noise Compensation(Boulder Regional Area Network fiber, 3.4 km)
1064 nm to NIST & back
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Synchronization between 2 fs lasers
-4
-2
0
2
4
Line
ar U
nit
2000150010005000pico-second
4
2
0
-25004003002001000
Phase control by 100 MHz PLL
Phase control by 8 GHz PLL
-4
-2
0
2
4
20x103 151050
picosecond4
2
0
-25004003002001000
Line
ar U
nit
Time (pico-second)
(a)
(d)(c)
(b)
Phase control by 100 MHz PLL
Phase control by 8 GHz PLL
(e)
Ye,Shelton
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SH
G(fr
om 1
00 M
Hz
lase
r)S
FG
0 100 200 300 ns
Arbitrary Repetition Rates
One laser running at 100 MHz, the other at 90 MHzThe resultant sum frequency repetition rate is 10 MHz
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Interference fringes between two femtosecond lasers
900850800750700
- Laser 1 spectrum- Laser 2 spectrum- Both lasers, not phase locked- Both lasers, phase locked
Spec
tral
Inte
rfer
omet
ry(L
inea
r Uni
t)
Wavelength (nm)
(a)
2nd-
orde
r Cro
ss-C
orre
latio
n
- Not phase locked- Phase locked(b)
(Lin
ear U
nit)
Delay Time (~ 2.6 fs per fringe)
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“Synthesized” Pulse A
uto-
Cor
rela
tion Laser 1
auto-correlation(a)
Aut
o-C
orre
latio
n
Delay Time
Laser 2auto-correlation
(b)
Aut
o-C
orre
latio
n auto-correlation;un-synchronized
(d) Combinedbeam
Aut
o-C
orre
latio
nDelay Time
(e) auto-correlation;synchronized
Combinedbeam
Aut
o-C
orre
latio
n
Delay Time
(f) auto-correlation;phase lockedCombined
beam
900850800750700
Spe
ctra
l Int
erfe
rom
etry
Wavelength (nm)
Spectralinterferometry
(c)
-Laser 1-Laser 2
Both lasers-No phase lock-Phase locked
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Switching signal
SFG intensity
Switching signal
SFG intensity
Record time (total 1 s)
Record time (total 1 ms)
SFG
Am
litud
e (a
rb. u
nit)
78 fs
50 µs
Delay
SFG
Am
litud
e (a
rb. u
nit)
(a) (b)
(c)
0
0
1
1
78 fsShelton, Ye, et alOpt. Lett. 27, 3121 Mar 2002
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g
Cancellation of Length Change,based on Symmetry!
600
500
400
300
200
100
0
x10-6
51.2551.2051.15x103
linewidth 1 Hzsidebands 18 & 5.5
Sub-Hertz Laser Linewidth-- on a Table Top !
PowerSpectrum
Delta OpticalFrequency(Hz)
L - ∆L
L + ∆L
Mass center surface
Mass center surface
Mass center surface
Vibration-Insensitive Reference Cavity
JILA/HallGroup_05
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Future Plans & OpportunitiesImproved Local Oscillators:
Stable Optical Reference + fs Laser Comb - “Gearbox” - better, & best
Already-demonstrated stability (1 s) 4 x10-14
vs H Maser (present LO for DSN) 3 x10-13
New Paradigm Frequency Counters simpler & better
fs laser gearbox + quartz + GPS 1 x10-14 at 1 day
Improved Physical Tests/MeasurementsGravity Gradient and Climate Explorer –II please use optical reference
LISA Gravitational Astronomy - heterodyne interferometry
Astrometric Interferometric Mission – curvature of local space, planet-finding
Local Lorentz Invariance – Special Relativity tests in zero –g
Clock Tests - “Alpha-dot,” Strong Force/Elect. & Mag., CPT: H vs anti-H
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Tutorial-type Background Refs
• “An introduction to phase-stable optical sources,” in International School of Physics 'Enrico Fermi', Course CXVIII, Laser Manipulation of Atoms and Ions (E. Arimondo, W. D. Phillips, and F. Strumia, Eds., North Holland, 1992), pp. 671-702.
• “Frequency stabilization of tunable lasers,” in Atomic, Molecular and Optical Physics: Electromagnetic Radiation (F. B. Dunning and R. G. Hulet, Eds., Experimental Methods in the Physical Sciences series, Vol. 29C, Academic, San Diego, 1997),103-36 with M. Zhu.
• “External Laser Stabilization,” John L. Hall, in Laser Physics at the Limit, a T. W. Haensch FestShrift, H. Figger, D. Meschede and C. Zimmermann, Eds., (Springer-Verlag, Berlin, 2002) pp. 51-59.
• "Optical Frequency Synthesis Based on Modelocked Lasers," S.T. Cundiff, J. Ye and J.L. Hall, Rev. Sci. Inst., 72, 3749-3771 (2001). (review paper).
• “Laser Stabilization,” J. L. Hall, M. Taubman and J. Ye,in OSA Handbook IV, Chapter 27 (2002).
[email protected]://jilawww.colorado.edu/Hall/