1. Rydberg excitation laser locking for spatial distribution measurement Graham Lochead 24/01/11

2. Outline Rydberg spatial distribution Coupling laser locking Cold atom experiments

3. Rydberg spatial distribution Ground stateRydberg state Distance (microns) Density (arb. units) V Low density High density

4. Experimental procedure Automatic translation stage Lens setup

5. Autoionization Allows independent Rydberg excitation and investigation Ion detection is very sensitive 5s 2 5s5p5sns(d)5pns(d)5s 1/2 +

6. 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

7. 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)

8. Frequency modulation spectroscopy CellEOM PS Oscilloscope G.C. Bjorklund et. al, Appl. Phys. B 32, 145-152 (1983) Filter 9.45 MHz

9. EIT locking difficulties Have to lock off- resonance Narrow absorption profile in cell Absorption quite low Cell 413 461

10. EIT locking solution Cell EOM PS Oscilloscope Problem: EIT signal too small Solution: Use an optical chopper Filter 9.45 MHz 413 Chopper Lock-in

11. EIT characterization

12. Cold atom setup Time Probe + Coupling (10 μs) MOT + Zeeman 10 μs Electric field pulse (10 μs) MOT + Zeeman Repeat

13. Spontaneous ionization with locked lasers Fit = 31 MHz Natural linewidth = 32 MHz Narrower – coherent population transfer Temperature = 6 mK Doppler width = 5 MHz

14. Outlook Can now lock both lasers Test autoionization SNR