rydberg excitation laser locking for spatial distribution measurement graham lochead 24/01/11
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Rydberg excitation laser locking for spatial distribution measurement
Graham Lochead 24/01/11
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Outline
• Rydberg spatial distribution
• Coupling laser locking
• Cold atom experiments
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Rydberg spatial distribution
Ground state Rydberg state
Distance (microns)
V
Lowdensity
Highdensity
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Experimental procedure
Automatictranslation stage
Lens setup
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Autoionization
• Allows independent Rydberg excitation and investigation
• Ion detection is very sensitive
5s2 5s5p 5sns(d) 5pns(d) 5s1/2+
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Progress towards experiment
Translation stage testing
Lens design and testing
Incorporation with main LabVIEW program
Laser locking
Rest of the optical layout
Test signal-to-noise of focussed autoionization pulse
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Laser locking
Need to lock coupling laser (5s5p → 5sns(d)) – previously stepped
Use modulation spectroscopy
Frequency (MHz)
Stepping gives incoherent transfer- Blockade harder to achieve
Autoionization laser will be stabilized using digital PID lock to the wavemeter
R.P. Abel et. al, Appl. Phys. Lett. 94, 071107 (2009)
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Frequency modulation spectroscopy
CellEOM
PS
Oscilloscope
G.C. Bjorklund et. al, Appl. Phys. B 32, 145-152 (1983)
Filter
9.45 MHz
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EIT locking difficulties
• Have to lock off-resonance
• Narrow absorption profile in cell
• Absorption quite lowCell
413
461
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EIT locking solution
CellEOM
PS
Oscilloscope
Problem: EIT signal too small
Solution: Use an optical chopper
Filter
9.45 MHz
413
Chopper
Lock-in
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EIT characterization
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Cold atom setup
Time
Probe +
Coupling
(10 μs)
MOT +
Zeeman 10 μs
Electric
field pulse
(10 μs)
MOT +
Zeeman
Repeat
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Spontaneous ionization with locked lasers
Fit = 31 MHz
Natural linewidth = 32 MHz
Narrower – coherent population
transfer
Temperature = 6 mK
Doppler width = 5 MHz
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Outlook
• Can now lock both lasers
• Test autoionization SNR