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

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(a) (b) Figure 7.33: Frequency-offset lock error signals. (a) Tapered amplifier master laser error signal. (b) Imaging laser error signal. 7.3.1.4 Tapered Amplifier Setup The tapered amplifier provides sufficient power for the MOT and the Zeeman slower beam. Additionally, the laser is used for imaging at zero magnetic field, where both MOT and repump frequency components are necessary for absorption imaging. It also provides a resonant beam used for various alignment procedures. The optical layout is shown in figure 7.34. To protect the tapered amplifier from back reflections an optical isolator (ConOp- tics, model 716) is placed behind the tapered amplifier output. Because tapered amplifier chips are even more sensitive to back-reflections than laser diodes, the isolation of this isolator is 56 to 60 dB. All other isolators in the setup have a 37 to 40 dB isolation. Even though the tapered amplifier beam is well collimated by a lens system inside the laser housing, the vertical and horizontal beam waists are different. To improve the beam profile, especially important to achieve good coupling efficiencies into fibers, a 5:3 cylindrical telescope optimizes the beam shape. Directly behind the cylindrical telescope, a 5:1 spherical telescope matches the beam diameter to the active area of two 114 MHz AOMs (IntraAction, ATM114-A1). Using a half-wave plate and a polarizing beam splitter cube, the beam from the tapered amplifier is split into two beam paths, the MOT and the repump arm. A typical ratio of powers is 3:1. The AOM in the MOT 125
Imaging ber Imaging ber from Imaging laser -40MHz AOM polarizing beam splitter cube 50:50 beam splitter cube mirror spherical lens cylindrical lens half-wave plate shutter ber coupler AOM +40MHz to beat lock setup additional resonant beam, e.g. for the small extra MOT beam for single atom detection f=50mm f=250mm f=60mm AOM f=100mm -114MHz optical isolator AOM +114MHz f=50mm f=50mm Figure 7.34: Optical layout of the tapered amplifier MOT ber 1 Tapered Amplier Zeeman slower ber AOM -80MHz MOT ber 3 f=150mm f=100mm MOT ber 2 arm shifts the laser frequency by −114 MHz, the AOM in the repump arm shifts the frequency by +114 MHz. Combined this produces a frequency difference of 228 MHz, the hyperfine splitting of the ground state of 6 Li. All three MOT beams and the Zeeman slower beam need a repump frequency component as well as the MOT frequency. The MOT arm and the repump arm are therefore recombined on a 50:50 beam splitter cube. To align the polarization of the two beams, a half-wave plate is added to the repump arm. One of the output ports of the 50:50 beam splitter cube provides the power for the three MOT beams, the second one provides the power for the Zeeman slower beam. In the beam path for the MOT beams, a series of half-wave plates and polarizing beam splitter cubes separate the beam into three beams. Each of these is individually coupled into a single-mode polarization-maintaining fiber. The beam of the second output port, used for the Zeeman slower beam, passes through another spherical telescope, again used to match the beam size to the active area of an 80 MHz AOM (IntraAction, AOM802). 126
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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
Page 91 and 92: effect of the reflected beam at zer
Page 93 and 94: y the repulsive trough beams, gaini
Page 95 and 96: Figure 5.9: Atom number as a functi
Page 97 and 98: 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: Thorlabs PDA10A Coupler ZDC-10-1 to
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 and 152: Feshbach coil objective lenses atom
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
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transitions for the excited state p
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Bibliography [1] J.J. Thomson. Cath
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[22] C.J. Foot. Atomic Physics. Oxf
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[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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