| 1. |
- Ellmann, Harald, 1971-
(author)
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Experimental Investigation of Three-Dimensional Single and Double optical Lattices
- 2002
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Doctoral thesis (other academic/artistic)abstract
- A complete laser cooling setup was built, with focus on threedimensional near-resonant optical lattices for cesium. These consist of regularly ordered micropotentials, created by the interference of four laser beams. One key feature of optical lattices is an inherent ”Sisyphus cooling” process. It efficiently extracts kinetic energy from the atoms, leading to equilibrium temperatures of a few µK. The corresponding kinetic energy is lower than the depth of the potential wells, so that atoms can be trapped.We performed detailed studies of the cooling processes in optical lattices by using the time-of-flight and absorption-imaging techniques. We investigated the dependence of the equilibrium temperature on the optical lattice parameters, such as detuning, optical potential and lattice geometry. The presence of neighbouring transitions in the cesium hyperfine level structure was used to break symmetries in order to identify, which role “red” and “blue” transitions play in the cooling. We also examined the limits for the cooling process in optical lattices, and the possible difference in steady-state velocity distributions for different directions. Moreover, in collaboration with ´Ecole Normale Sup´erieure in Paris, numerical simulations were performed in order to get more insight in the cooling dynamics of optical lattices.Optical lattices can keep atoms almost perfectly isolated from the environment and have therefore been suggested as a platform for a host of possible experiments aimed at coherent quantum manipulations, such as spin-squeezing and the implementation of quantum logic-gates. We developed a novel way to trap two different cesium ground states in two distinct, interpenetrating optical lattices, and to change the distance between sites of one lattice relative to sites of the other lattice. This is a first step towards the implementation of quantum simulation schemes in optical lattices.
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| 2. |
- Ellmann, Harald, et al.
(author)
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Experiments with a 3D Double Optical Lattice
- 2003
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 90:5, s. 053001-
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Journal article (peer-reviewed)abstract
- We present a setup where we trap two different cesium hyperfine ground states in two different near-resonant optical lattices with identical topographies. We demonstrate that we can change the relative spatial phase between the lattices and we measure the equilibrium temperature as a function of the relative spatial phase. This provides a topographical chart of the optical potential. We also determine the rate at which atoms are transferred between the lattices and show that the setup is a promising candidate for implementing coherent quantum state manipulation.
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| 3. |
- Ellmann, Harald, et al.
(author)
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Experiments with a 3D double optical lattice
- 2003
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In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 90:5
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Journal article (peer-reviewed)abstract
- We present a setup where we trap two different cesium hyperfine ground states in two different near-resonant optical lattices with identical topographies. We demonstrate that we can change the relative spatial phase between the lattices and we measure the equilibrium temperature as a function of the relative spatial phase. This provides a topographical chart of the optical potential. We also determine the rate at which atoms are transferred between the lattices and show that the setup is a promising candidate for implementing coherent quantum state manipulation.
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| 4. |
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| 5. |
- Ellmann, Harald, et al.
(author)
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Temperatures in 3D optical lattices influenced by neighbouring transitions
- 2001
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In: European Physical Journal D. - 1434-6060 .- 1434-6079. ; 13:3, s. 379-384
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Journal article (peer-reviewed)abstract
- A detailed experimental study of the steady-state temperature in a 3D optical lattice for cesium has been performed for a wide range of detunings. Specifically, we have investigated the situation with the cooling and trapping light detuned far red of a (J(g) --> J(e) = J(g) + 1)-transition, where the blue detuned interaction with a (J(g) --> J(e) = J(g))-transition can not be neglected. We find that the temperature scales with the optical potential due to the interaction with just the (J(g) --> J(e) = J(g) + 1)-transition. This indicates that blue Sisyphus cooling has essentially no effect on the dynamics of the system, when there exists a neighbouring red detuned transition.
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| 6. |
- Jersblad, Johan, et al.
(author)
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Anisotropic velocity distributions in 3D dissipative optical lattices
- 2003
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In: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 22:3, s. 333-339
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Journal article (peer-reviewed)abstract
- We present a direct measurement of velocity distributions in two dimensions by using an absorption imaging technique in a 3D near resonant optical lattice. The results show a clear difference in the velocity distributions for the different directions. The experimental results are compared with a numerical 3D semi-classical Monte-Carlo simulation. The numerical simulations are in good qualitative agreement with the experimental results.
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| 7. |
- Jersblad, Johan, et al.
(author)
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Experimental investigation of the limit of Sisyphus cooling
- 2000
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 62:5
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Journal article (peer-reviewed)abstract
- We present measurements of the steady-state temperature in a three-dimensional cesium optical lattice, operating in the near-resonance regime of the D2 line. For various detunings between the (F-g=4 -->F-e=5) and the (F-g=4 -->F-e=4) transitions, we systematically determine at which intensities/optical potential modulation depths the Sisyphus cooling process breaks down and what the lowest achievable temperatures are. We find that the minimum temperature decreases as we increase the detuning with respect to the (F-g=4 -->F-e=5) transition.
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