Graham Lochead07/09/09

Pulsed laser spectroscopy in strontium

Graham Lochead07/09/09

Outline

• Strontium project update

• Ladder EIT

• Electron shelving spectroscopy

Graham Lochead07/09/09

Project update

• Pyramid MOT

• Cavity

• 412 nm laser

• 420 nm laser

Graham Lochead07/09/09

Optical setup

Cell461 nm light from fibre

FPD

Aperture

Dispenser Baffle

Lens

• ~5 mm beam diameter• 10 Hz repetition• 10 ns pulse duration

• ~20 mJ per pulse• ~5 nm tuning range• ~2 GHz linewidth

Dye laser parameters

Pump laser

Dye laser

Graham Lochead07/09/09

Ladder EIT (I)

Probe: 5s2 1S0 → 5s5p 1P1

Couple: 5s5p1P1 → 5snd1D2

)(2/0

2/2/

02/0

cpc

cpp

p

5s2 1S0

5s5p 1P1

5snd 1D2

lg>

le>

lr>

461 nm

413 nm

1P1 lifetime ~ 5 ns, Rydberg lifetime ~ 10 μs

rree rea ..2

cheregee tic

tipi

cp

epp

rcc

ωe

ωr

ωp

ωc

Δp

Δc

J.P. Marangos, J. Mod. Opt 45, p. 471-503 (1998)

Graham Lochead07/09/09

Ladder EIT (II)

reg sincoscossinsin

reg coscossincossin

rg sincos0

Diagonalization of the Hamiltonian leads to new eigenstates:

c

p

arctan

p

cp

22

arctan2

1

For Ωc >> Ωp and Δp = 0

2er

2er

g0

Probe couples to excited state of both |+> and |-> which have equal but opposite transition probabilities, thus on-resonance probe not absorbedCoherent process – decoherence effects increase absorption

Graham Lochead07/09/09

Simulations

• Solve three level optical Bloch equations

• Rydberg transition Rabi frequency from oscillator strength S.-U. Haq et al., EPJD 44, p. 439 (2007)

)(

4/

1

31

2

21cp

p ii

Absorption

Graham Lochead07/09/09

Catastrophe!

• Hole drilled in viewport• Vacuum lost

Hole • Cell cleaned out• Reassembled and re-

evacuated• Absorption seen again

Graham Lochead07/09/09

Electron shelving

Off-resonant two photon excitation to Rydberg state5s2 1S0

5s5p 1P1

5snd 1D2

ΩpΩc

461 nm

435 nm

435 nm

P. Thoumany et al., Optics Letters 34, p. 1621-1623 (2009)

Probe: 5s2 1S0 → 5s5p 1P1

Couple: 5s2 1S0 → 5snd 1D2

Unlikely to see EIT due to large decoherence

Rydberg state has a long lifetime relative to 1P1

Graham Lochead07/09/09

Outlook

• Change dye to attempt electron shelving

• Finish building pyramid MOT