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
Outline
• Rydberg spatial distribution
• Coupling laser locking
• Cold atom experiments
Rydberg spatial distribution
Ground state Rydberg state
Distance (microns)
V
Lowdensity
Highdensity
Experimental procedure
Automatictranslation stage
Lens setup
Autoionization
• Allows independent Rydberg excitation and investigation
• Ion detection is very sensitive
5s2 5s5p 5sns(d) 5pns(d) 5s1/2+
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
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)
Frequency modulation spectroscopy
CellEOM
PS
Oscilloscope
G.C. Bjorklund et. al, Appl. Phys. B 32, 145-152 (1983)
Filter
9.45 MHz
EIT locking difficulties
• Have to lock off-resonance
• Narrow absorption profile in cell
• Absorption quite lowCell
413
461
EIT locking solution
CellEOM
PS
Oscilloscope
Problem: EIT signal too small
Solution: Use an optical chopper
Filter
9.45 MHz
413
Chopper
Lock-in
EIT characterization
Cold atom setup
Time
Probe +
Coupling
(10 μs)
MOT +
Zeeman 10 μs
Electric
field pulse
(10 μs)
MOT +
Zeeman
Repeat
Spontaneous ionization with locked lasers
Fit = 31 MHz
Natural linewidth = 32 MHz
Narrower – coherent population
transfer
Temperature = 6 mK
Doppler width = 5 MHz
Outlook
• Can now lock both lasers
• Test autoionization SNR