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

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The laser diode (Intelite MLD-780-100S5P) has a wavelength of 780 nm and an output power of 100 mW at a current of 120 mA. The diode is mounted into the cavity by placing it in a collimation tube (Thorlabs LT230P-B). This tube also houses a broadband AR coated aspheric lens (f = 4.5 mm) to collimate the output beam. The collimated beam hits a gold-coated, blazed diffraction grating with 1200 grooves/mm. The zeroth- order specular reflection serves as the output beam. The first-order diffracted beam is reflected back into the diode laser, completing the external laser cavity. The laser frequency can be adjusted by changing the grating angle using a piezo stack. Thermal stability is provided by actively stabilizing the temperature of the bronze baseplate of the external cavity diode laser with a thermo-electric cooler (TEC) and a PID feedback loop. The whole setup is housed in a plexiglass cover to isolate the laser from air currents and acoustic vibrations. Figure 4.7: MOT master laser. After the beam exits the diode laser housing the beam asymmetry is removed by an anamorphic prism pair. To protect the laser from damage due to back reflec- tions, the beam passes through an optical isolator (ConOptics 712B). The beam then passes through an AOM with a frequency of 103 MHz. Only a few milliwatts of power are diffracted in this AOM, just enough to provide sufficient light for the saturated absorption spectroscopy setup used to stabilize the laser frequency. A schematic of the 53
distribution of the MOT master laser is shown in figure 4.8. error signal from lock-box MOT master laser λ/2 λ/2 optical isolator anamorphic prism pair AOM @ 103 MHz to saturation absorption spectrometer +1 λ/4 λ/2 +1 to slave lasers to Fabry-Perot cavity PBSC AOM @ 80 MHz Figure 4.8: Distribution fo the MOT master laser. Figure courtesy of Gabriel Price. Figure 4.9 shows the layout of the saturated absorption spectroscopy setup used to lock the MOT master laser. The beam is split into a pump and a probe beam using an uncoated glass plate. This ensures that the probe beam is significantly weaker than the pump beam. The pump beam is deflected by a polarizing beam splitter cube and double passes a 44 MHz AOM. This AOM is modulated with a frequency of 7 kHz and a modulation depth of 4 MHz. In the double pass the polarization of the beam is rotated by 90 ◦ , passing a quarter waveplate twice. On the second incidence on the polarizing beam splitter cube the pump beam thus passes through the cube and into the rubidium vapor cell. The pump beam is therefore counter-propagating the probe beam. At the same cube the probe beam is deflected and the signal is recorded with a fast photodiode. The signal is mixed with the FM frequency at a lock-in amplifier (Stanford Research Systems, SR510). The error signal that results from sweeping the laser across the |F = 2〉 → |F ′ = 3〉 transition is shown in figure 4.10. The laser is locked to the |F = 2〉 → |F ′ = 2/3〉 crossover line, as this is the most prominent feature. The error signal is fed into a PID circuit and amplified by a high-voltage amplifier (Trek 601B-2) to feed back onto the grating angle. 54
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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 .
Page 19 and 20: The development of techniques to la
Page 21 and 22: Ptorr 10 5 10 6 10 7 10 8 10 9 260
Page 23 and 24: Property Symbol Value Reference Ato
Page 25 and 26: 2.3.2 Hyperfine Structure So far th
Page 27 and 28: The Wigner-Eckhart theorem can be u
Page 29 and 30: The total magnetic moment of an ato
Page 31 and 32: interaction. The shift in the energ
Page 33 and 34: (a) (b) scattering length a 0 Energ
Page 35 and 36: a laser field with frequency ω. Th
Page 37 and 38: Here ω0 is the resonance frequency
Page 39 and 40: Optical molasses do not provide a s
Page 41 and 42: J=1 J=0 -1 Δ σ + σ - σ - 0 +1 -
Page 43 and 44: phase-space density is defined as
Page 45 and 46: which maintains a constant η = U/k
Page 47 and 48: 2.12.1 Saturated Absorption Spectro
Page 49 and 50: Figure 2.22: Saturation absorption
Page 51 and 52: Signal 0 Signal (a) (b) Signal Freq
Page 53 and 54: (a) (b) (c) (d) Figure 2.24: Absorp
Page 55 and 56: y more complex energy level structu
Page 57 and 58: ight side of the box. An irreversib
Page 59 and 60: time (a) (b) (c) Figure 3.3: Single
Page 61 and 62: them to move from B to A, but close
Page 63 and 64: Figure 4.1: Vacuum chamber. Photogr
Page 65 and 66: ( ( Figure 4.3: Helicoflex seal. (a
Page 67 and 68: 88 mm 4.2.3 Auxiliary Coils 62 mm Q
Page 69: 5 2 P 3/2 5 2 S 1/2 384. 230 484 46
Page 73 and 74: shifts. First a frequency shift of
Page 75 and 76: transition. However, the laser freq
Page 77 and 78: 4.3.1.4 Upper MOT Horizontal Slave
Page 79 and 80: provides the beam for the upper MOT
Page 81 and 82: demon beam λ λ horizontal MOT bea
Page 83 and 84: scholar, Florian Schreck. It is wri
Page 85 and 86: Atoms are then optically pumped to
Page 87 and 88: ferred into the |F = 1,mF = 0〉 or
Page 89 and 90: 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
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Figure 7.12: The assembled Zeeman s
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7.2.2 MOT Coils A second set of coi
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BGauss 250 200 150 100 50 30 20 10
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are required to create the high mag
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The coils are then checked for shor
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+ B A Figure 7.23: Feshbach coil H-
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ensure that no particulates build u
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118 Figure 7.26: Optical layout of
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The error signal shows three lines,
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into the CO2 laser. The optical lay
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Thorlabs PDA10A Coupler ZDC-10-1 to
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Imaging ber Imaging ber from Imagin
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Table 7.4 summarizes the beam power
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CO2 laser 40 MHz AOM f=2 in f=2 in
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132 Figure 7.38: Optical layout aro
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Feshbach coil objective lenses atom
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MOT beams are no longer traveling a
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The second card (NI6733) offers eig
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Averaging over the magnetic subleve
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2 2 P 3/2 D 2=670.977nm 2 2 S 1/2 m
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The right hand side of equation 7.1
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= E0 1 −n2 √2 exp σ0 ± iE0
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esidual potentials besides gravitat
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Figure 8.1: MOT loading. Typical lo
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A linear ramp typically changes the
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A typical MOT is density-limited at
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ubidium [113-115] and cesium[116].
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that most of the noise is due to th
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(a) (c) y . x z X=0.0mm Z=2.5mm 1)
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Figure 8.11: Different shapes of MO
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ZnSe lens f=5 in knife edge ZnSe wi
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shown in figure 8.13. By matching t
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Figure 8.15: Atom number and temper
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275 Hz. Using these values the beam
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system. Maybe the easiest way to ac
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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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