Experiments to Control Atom Number and Phase-Space Density in ...

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polarizing beam splitter cube xed ratio beam splitter cube dichroic mirror pinhole photodiode APD quarterwave plate Figure 7.40: Optics along the vertical axis. The main MOT beam is shown in blue, the small MOT beam is shown in orange, the YAG tweezer beam is shown in green, and the scattered light collection is shown in red. There is however one more problem that needs to be addressed by the objective. In order to detect single atoms, the atoms will have to be trapped in a small MOT and excited so that they scatter photons. This means that a small MOT beam is required along the vertical axis even during single-atom detection. To overcome this problem part of the lenses had to be removed to allow for the alignment of a small MOT beam at an angle of 38 ◦ relative to the vertical axis. That way the scattered photons and the 135
MOT beams are no longer traveling along the same beam path. In addition, the outer diameter of the meniscus lens has to be reduced for the lens to fit close enough to the vacuum viewport. The final diameter of the lens is 40 mm. These modifications to the lenses were done in the physics department machine shop. Special care had to be taken that the AR coating of the lenses would not be damaged during the machining process. Photographs of the lenses are shown in figure 7.41. (a) (b) Figure 7.41: Photograph of the objective lenses: a) Meniscus lens. b) Aspheric lens. The two lenses are housed in a specially designed objective holder. The meniscus lens sits at the bottom of the holder and is held in place by a Delrin sleeve. This sleeve also houses the aspheric lens. This Delrin sleeve allows for easy mounting of the aspheric lens inside the objective holder. It also determines the distance between the meniscus lens and the aspheric lens. The asphere is fixed to the objective holder by set screws. After the lenses are machined and assembled inside the objective holder, the performance of the objective is tested by measuring the final waist of a YAG laser beam. The YAG laser is first fiber-coupled into a single-mode polarization-maintaining fiber and then collimated to a waist of 8.4 mm using an achromat doublet lens (Thorlabs AC254- 100). To simulate the reentrant viewport window, a window of the same thickness and material is implemented into the test setup. Even without optimizing the alignment, waists of 2.1 µm and 2.0 µm are measured horizontally and vertically. Two beam splitter cubes, the first a polarizing beam splitter cube, and the second a fixed ratio beam splitter cube, shown in figure 7.40 can be used to stabilize the beam power in the YAG using a PID feedback loop. The first beam splitter cleans the polar- 136
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Copyright by Kirsten Viering 2012
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Experiments to Control Atom Number
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Acknowledgments First of all, I wou
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Experiments to Control Atom Number
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Table of Contents Acknowledgments v
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Chapter 7. Lithium Apparatus 92 7.1
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List of Tables 2.1 Physical propert
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4.1 Vacuum chamber . . . . . . . .
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7.39 Future vertical axis optics .
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The development of techniques to la
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Ptorr 10 5 10 6 10 7 10 8 10 9 260
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Property Symbol Value Reference Ato
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2.3.2 Hyperfine Structure So far th
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The Wigner-Eckhart theorem can be u
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The total magnetic moment of an ato
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interaction. The shift in the energ
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(a) (b) scattering length a 0 Energ
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a laser field with frequency ω. Th
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Here ω0 is the resonance frequency
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Optical molasses do not provide a s
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J=1 J=0 -1 Δ σ + σ - σ - 0 +1 -
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phase-space density is defined as
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which maintains a constant η = U/k
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2.12.1 Saturated Absorption Spectro
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Figure 2.22: Saturation absorption
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Signal 0 Signal (a) (b) Signal Freq
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(a) (b) (c) (d) Figure 2.24: Absorp
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y more complex energy level structu
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ight side of the box. An irreversib
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time (a) (b) (c) Figure 3.3: Single
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them to move from B to A, but close
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Figure 4.1: Vacuum chamber. Photogr
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( ( Figure 4.3: Helicoflex seal. (a
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88 mm 4.2.3 Auxiliary Coils 62 mm Q
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5 2 P 3/2 5 2 S 1/2 384. 230 484 46
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distribution of the MOT master lase
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shifts. First a frequency shift of
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transition. However, the laser freq
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4.3.1.4 Upper MOT Horizontal Slave
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provides the beam for the upper MOT
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demon beam λ λ horizontal MOT bea
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scholar, Florian Schreck. It is wri
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Atoms are then optically pumped to
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ferred into the |F = 1,mF = 0〉 or
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5.2 Branching Ratios and Population
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effect of the reflected beam at zer
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y the repulsive trough beams, gaini
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Figure 5.9: Atom number as a functi
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Figure 5.10: Radius of the magnetic
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on the collision rate of atoms insi
Page 101 and 102: ferred via the single-photon coolin
Page 103 and 104: By comparison an atomic Fock state
Page 105 and 106: of atoms in the two hyperfine groun
Page 107 and 108: difference in the lifetimes is dete
Page 109 and 110: Chapter 7 Lithium Apparatus Creatin
Page 111 and 112: angle valve rotary feedthrough ion
Page 113 and 114: an ion gauge controller (Granville
Page 115 and 116: viewports (MDC, 450002) are attache
Page 117 and 118: not trapped by the MOT impinge on t
Page 119 and 120: Should contamination of the vacuum
Page 121 and 122: Figure 7.12: The assembled Zeeman s
Page 123 and 124: 7.2.2 MOT Coils A second set of coi
Page 125 and 126: BGauss 250 200 150 100 50 30 20 10
Page 127 and 128: are required to create the high mag
Page 129 and 130: The coils are then checked for shor
Page 131 and 132: + B A Figure 7.23: Feshbach coil H-
Page 133 and 134: ensure that no particulates build u
Page 135 and 136: 118 Figure 7.26: Optical layout of
Page 137 and 138: The error signal shows three lines,
Page 139 and 140: into the CO2 laser. The optical lay
Page 141 and 142: Thorlabs PDA10A Coupler ZDC-10-1 to
Page 143 and 144: Imaging ber Imaging ber from Imagin
Page 145 and 146: Table 7.4 summarizes the beam power
Page 147 and 148: CO2 laser 40 MHz AOM f=2 in f=2 in
Page 149 and 150: 132 Figure 7.38: Optical layout aro
Page 151: Feshbach coil objective lenses atom
Page 155 and 156: The second card (NI6733) offers eig
Page 157 and 158: Averaging over the magnetic subleve
Page 159 and 160: 2 2 P 3/2 D 2=670.977nm 2 2 S 1/2 m
Page 161 and 162: The right hand side of equation 7.1
Page 163 and 164: = E0 1 −n2 √2 exp σ0 ± iE0
Page 165 and 166: esidual potentials besides gravitat
Page 167 and 168: Figure 8.1: MOT loading. Typical lo
Page 169 and 170: A linear ramp typically changes the
Page 171 and 172: A typical MOT is density-limited at
Page 173 and 174: ubidium [113-115] and cesium[116].
Page 175 and 176: that most of the noise is due to th
Page 177 and 178: (a) (c) y . x z X=0.0mm Z=2.5mm 1)
Page 179 and 180: Figure 8.11: Different shapes of MO
Page 181 and 182: ZnSe lens f=5 in knife edge ZnSe wi
Page 183 and 184: shown in figure 8.13. By matching t
Page 185 and 186: Figure 8.15: Atom number and temper
Page 187 and 188: 275 Hz. Using these values the beam
Page 189 and 190: system. Maybe the easiest way to ac
Page 191 and 192: Appendix A Magic Wavelength of Hydr
Page 193 and 194: transitions for the excited state p
Page 195 and 196: Bibliography [1] J.J. Thomson. Cath
Page 197 and 198: [22] C.J. Foot. Atomic Physics. Oxf
Page 199 and 200: [46] E.D. Black. An introduction to
Page 201 and 202: [67] J.L. Hanssen. Controlling Atom
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[88] D.S. Naik, C.G. Peterson, A.G.
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[110] J.W. Goodman. Introduction to
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[132] C. Degenhardt, H. Stoehr, U.
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