Transcript Slide 1
Spatial distributions in a cold strontium Rydberg gas Graham Lochead The group Matt Jones Charles Adams Liz Bridge James Millen Danielle Boddy Daniel Christophe Sadler Vaillant Graham Lochead 28/01/13 Rydberg Dipole blockade Strong, tunable interactions M. Saffman et al., Rev. Mod. Phys. 82 2313 (2010) C.L. Vaillant et al., J. Phys. B 45 135004 (2012) Graham Lochead 28/01/13 Dipole blockade spatial effects Excited state Column density Autocorrelation Ground state Radius (μm) Position A. Schwartzkopf et al., Phys. Rev. Lett. 107, 103001 (2011) Graham Lochead 28/01/13 Further spatial effects Dynamical crystallisation P. Schauß et al., Nature 491, 87 (2012) T. Pohl et al., Phys. Rev. Lett. 104, 043002 (2010) Graham Lochead 28/01/13 Outline • CPT in cold strontium atoms • Optical Bloch equation model • Autoionization microscopy • Spatial electrometry Graham Lochead 28/01/13 Cold atom source • Zeeman slowed atomic beam • 107 strontium atoms at 5 mK • 5 x 109 atoms/cm3 Graham Lochead 28/01/13 CPT spectra • Coupling laser locked • Probe laser frequency stepped • E-field does not field ionize • Sub-natural linewidth • Data for n = 56 Graham Lochead 28/01/13 Optical Bloch Equations 5snd Ωc 5s5p Free parameters • Laser linewidths • Rabi frequencies • Laser detuning • State linewidths • Amplitude scaling Ωp Fixed parameters 5s2 Graham Lochead 28/01/13 Focus coupling laser Fewer Rydberg atoms – reduced spontaneous ionization Spatial intensity variation of beam makes a difference Graham Lochead 28/01/13 Spatial information Translate a focused autoionizing beam Graham Lochead 28/01/13 Lens setup 100 mm long 10 μm resolution Graham Lochead 28/01/13 Rydberg spatial distribution • Ground state fluorescence collected • Can take distributions in both directions Graham Lochead 28/01/13 Spatial widths: Coupling power OBE simulation Autoionizing probability Graham Lochead 28/01/13 Electrometry Use Stark effect to alter Rydberg distribution Spatially varying detuning G. Lochead et al., arXiv:1212.3270 Graham Lochead 28/01/13 Future work Increase density with further cooling 1P 3P 1 3P λ = 461 nm Γ = 2π x 32 MHz 1st stage cooling 3P 2 Excite using the triplet lines 1 0 λ = 689 nm Γ = 2π x 7.5 kHz 2nd stage cooling 1S 3S(D) λ2 = 319 nm 3P 0 Blue MOT: ~ 5 mK ~ 2 x 109 atoms/cm3 Red MOT: ~ 400 nK ~ 2 x 1012 atoms/cm3 Graham Lochead 28/01/13 0(2) 1 λ1 = 689 nm 1S 0 Summary • Coherently excite strontium atoms to Rydberg states • Optical Bloch equation model works • 10 µm resolution spatial distribution • Sensitive spatial electrometric technique Graham Lochead 28/01/13