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

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factor of 4. To image the MOT and measure its temperature this magnification is too large, and another lens (f = 50 mm) is added to the setup, changing the magnification to 0.5. A fire-wire camera (Allied Vision Technologies, Stingray F-33B/C) records the image along this axis. For imaging atoms in the CO2 beam this lens is removed from the setup. A second imaging axis, mostly used for fluorescence imaging, is at a slight axis of the direction of MOT beam 1. A mirror mounted as close as possible to the MOT beam and a f = 150 mm lens collect the light and image it onto the CCD camera (Alta U47+). A retro-reflected MOT beam is currently the only beam using the vertical axis. 7.3.4 Laser Culling Dipole Trap Setup The vertical axis will be used in the near future for a number of different purposes. Most importantly, it is the axis along which the small tweezer beam used for laser culling will be focused into the degenerate Fermi gas. To focus this laser beam a self-designed objective consisting of an aspheric lens and a meniscus lens was designed. A schematic of the setup within the reentrant viewport is shown in figure 7.39. In addition this axis will be used to collect the fluorescence light for single- and few-atom detection. Of course the third MOT beam will still be along this axis as well. The custom objective therefore has to fulfill many requirements: The working distance has to be larger than 14.3 mm, the spot size should be as small as possible, the numerical aperture should be as large as possible to collect as many photons as possible, and the MOT beam has to be retro-reflected. The objective consists of two stock lenses, an aspheric lens (Thorlabs AL4532-B) and a meniscus lens (CVI MellesGriot MENP- 50.0-4.8-300.0-C-670-1064) and is designed using Zemax optical design software. The diffraction limited beam waist of this objective using a YAG beam with a waist of 8 mm is exptected to be 1.7 µm. The spacing between the two lenses is 2 mm. To focus at the location of the atoms the objective needs to be mounted 2.8 mm above the window of the reentrant viewport. 133
Feshbach coil objective lenses atoms reentrant viewport vacuum chamber Figure 7.39: Future vertical axis optics. The Nd:YAG tweezer beam will be focused through the objective lens unto the atoms. The MOT beam will come from the bottom and be retroreflected above the vacuum chamber with the help of additional optics. The objective will also be used to collect the fluorescence signal for single-atom detection. In principle aspheric lenses are designed to minimize aberrations to generate the smallest spot size possible. However, these lenses are not designed having the glass of the vacuum viewport in mind. The meniscus lens is therefore added to compensate for the effect of that window. The objective will also be used to collect the fluorescence light for single-atom detection. A large numerical aperture of the objective is therefore important and the diameter of the objective lenses should be kept as large as possible. With this objective it is expected to collect about 10% of the scattered photons. These photons can then be spatially filtered and focused onto the avalanche photo diode (APD, Perkin Elmer, SPCM-AQR-14) for single-atom detection. A dichroic mirror combines the YAG beam and the scattered photon beam paths. The MOT beam will be focused by the objective lens. Additional lenses can recollimate the beam, before it is retro-reflected. An optical layout of the envisioned optical setup is shown in figure 7.40. A mirror required for the MOT loading stage can be moved away after the MOT is loaded. 134
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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
Page 99 and 100: 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: 132 Figure 7.38: Optical layout aro
Page 153 and 154: MOT beams are no longer traveling a
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
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[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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