rydberg excitation laser locking for spatial distribution measurement graham lochead 24/01/11

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