optic rotation project i doppler-free saturated absorption spectrum lei huang
DESCRIPTION
Optic Rotation Project I Doppler-free saturated absorption spectrum Lei Huang Department of Physics and Astronomy SUNY at Stony Brook May. 4 th , 2005. Doppler Effect in absorption spectroscopy. Maxwell velocity distribution. Sharp absorption line get broadened!. - PowerPoint PPT PresentationTRANSCRIPT
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Optic Rotation Project I
Doppler-free saturated absorption spectrum
Lei Huang
Department of Physics and Astronomy
SUNY at Stony Brook
May. 4th, 2005
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Doppler Effect in absorption spectroscopy
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
Maxwell velocity distribution
ZZ
ZZ dVkT
MV
kT
MdVVP )
2exp()
2()(
22/1
Sharp absorption line get broadened!
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Doppler-free absorption spectroscopy
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
• Crossover transition peaks stronger than original transition peaks• pumping beam can create hyperfine pumping and saturation
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External Cavity Diode Laser (ECDL) & Grating Feedback
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
Laser Diode
GratingPZT
heat sink
Littrow Configuration for grating feedback:
Ldi
di
d
dm
2sin2, :order1st
)sin(sin
0th order: laser output1st order: grating feedback
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Optical Circuitry Layout
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
Rb cell
Optic Isolator
Photo Diode
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Temperature• change laser diode bandgap → coarse tuning• time-consuming • 4GHz / 0C
Injection Current• shift and select the lasing mode• 40 MHz / mA
Voltage bias applied on PZT• wave generator + amplifying circuit• offset → displacement• amplitude → range• DC voltage → limit
Tunable Parameters
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
Reduction ratesVosc:VPZT=1:100
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87Rb energy levels
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
...)(42 0
22
IJSLrr
eZ
m
pH eff
Hamiltonian:
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Rubidium spectrum
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
85Rb:72%, I=5/2,Ground states F=2,3
87Rb:28%, I=3/2,Ground states F=1,2
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Coarse position tuning
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
“flashing” maximal frequency sweeping
87Rb F=2→F’ 85Rb F=3→F’ Doppler-broadened absorption spectrum
Some periodic patterndue to laser output frequency hops
Fix the temperature and triangle wave voltage, tuning the injection current continuously within a small range
Parameters:Temp=22.70CAmp=2.12VOffset=1.84VCurr.=78.5A,78.8A
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87Rb F=2→F’ fine structure
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
F’=3 F’=2 F’=1
Parameters:Temp=22.70CAmp=1.09VOffset=1.77VCurr.=79.0A
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85Rb F=3→F’ fine structure
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
F’=4 F’=3 F’=2
Parameters:Temp=22.70CAmp=1.31VOffset=2.24VCurr.=78.6A
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Quantitative Analysis
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
For 85Rb F=3→F’channel 2Horizontal 8.5div, vertical 262V262V/8.5div = 30.8V/div
Horizontal scale zoom-in 2.5 times
Two strongest peaks 30MHz/0.4div=75MHz/divBefore zoom-in: 187.5MHz/divSo, the response for output f to PZT V is225MHz/30.8V=6.1MHz/V
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Quantitative Analysis
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
For 87Rb F=2→F’channel 2Horizontal 8.5div, vertical 218V218V/8.5div = 25.7V/div
Horizontal scale zoom-in 3 times
2nd and 3rd strongest peaks 128.6MHz/3.5div=36.7MHz/divBefore zoom-in: 110MHz/divSo, the response for output f to PZT V is110MHz/25.7V=4.28MHz/V
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Quantitative Analysis
Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
Finally, the response for output frequency to PZT Voltage is about 5.2+/-0.9 MHz/V
Back to our coarse position tuning,424V of scanning voltage amplitude corresponds to 2.205GHz of frequency sweeping range, thus can only reveal two neighboring Doppler-broadened absorption peaks.
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Lei Huang, Optic Rotation Project 1, Rb spectroscopy, May 4th,2005
References
• Daryl W. Preston, “Doppler-Free Saturated Absorption”, ELECTRO-OPTIC EXPERIMENTS FOR THE ADVANCED LABORATORY, 2000
• Bob Azmoun and Susan Metz, “RECIPE FOR LOCKING AN
EXTENDED CAVITY DIODE LASER FROM THE GROUND UP”, http://laser.physics.sunysb.edu/~bazmoun/RbSpectroscopy/
• Jan Max and Walter Kruger, “A NOVEL TECHNIQUE FOR FREQUENCY STABILISING LASER DIODES”, http://hubble.physik.uni-konstanz.de/jkrueger/thesis/thesis.html/
• Rita Kalra, experiment log book in Laser Teaching Center