The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Alkali-Metal Atoms in Laser Fields: Optical Pumping, Coherent Population Trapping, and Laser Cooling

Thomas Lindvall

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium TU2 at the Aalto University School of Science and Technology (Espoo, Finland) on the 10th of December 2010 at 12 noon.

Overview in PDF format (ISBN 978-952-60-3502-4)   [1948 KB]
Dissertation is also available in print (ISBN 978-952-60-3501-7)

Abstract

Alkali metals have played an important role in optical and atomic physics from the very beginning. This thesis deals with three aspects and applications of alkali-metal atoms, in particular rubidium (Rb).

Optical pumping changes both the amplitudes and the center positions of the absorption profiles in the Doppler-broadened D-line spectra of the alkali-metal atoms. This effect has been studied by reducing the multilevel system to an effective three-level system and by treating the finite interaction time and collisions with the vapor-cell walls in two different ways: as ground-state relaxation and by averaging the time-dependent absorption over the distribution of interaction times. The former is a computationally efficient way to compare theoretical spectra to experimental results, and the latter reveals lineshape details that are due to the coupling between the Doppler shift and the interaction times through the longitudinal velocity of the atoms.

Using coherent population trapping (CPT) in 85Rb, an all-optical atomic clock has been realized. The good noise properties of the diode laser, an optimized buffer gas, and a very low light intensity allow detection of ultranarrow CPT resonances < 20 Hz, apparently the narrowest optically induced hyperfine CPT resonance ever measured. The Q value of this resonance, 1.5 × 108, is comparable to Q values in cesium clocks and the stability of the CPT clock is sufficient for many high-precision applications.

Trapping of Rb atoms in microscopic magneto-optical traps (MOTs) a few hundred micrometers from the surface of an optically transparent ferrite-garnet permanent-magnet atom chip has been demonstrated. The required magnetic fields are created by magnetic patterns magneto-optically written into the ferrite-garnet film and the transparency of the chip allows using a conventional MOT geometry. The magnetic patterns can be erased and re-written in situ, even during the experiments. Magnetic traps with a trap depth up to 1 mK could be realized using this type of atom chip.

This thesis consists of an overview and of the following 5 publications:

  1. T. Lindvall and I. Tittonen. 2007. Effect of optical pumping on alkali-atom Doppler-limited spectra. Journal of Modern Optics, volume 54, numbers 16-18, pages 2779-2793. Corrigendum. 2008. Journal of Modern Optics, volume 55, number 15, pages 2497-2500.
  2. Thomas Lindvall and Ilkka Tittonen. 2009. Interaction-time-averaged optical pumping in alkali-metal-atom Doppler spectroscopy. Physical Review A, volume 80, number 3, 032505, 10 pages. © 2009 American Physical Society (APS). By permission.
  3. T. Lindvall, M. Merimaa, I. Tittonen, and E. Ikonen. 2002. All-optical atomic clock based on dark states of 85Rb. In: Patrick Gill (editor). Proceedings of the 6th Symposium on Frequency Standards and Metrology (FSM 2001). Fife, Scotland, UK. 9-14 September 2001. Singapore. World Scientific Publishing Company. Pages 183-190. ISBN 981-02-4911-X.
  4. Mikko Merimaa, Thomas Lindvall, Ilkka Tittonen, and Erkki Ikonen. 2003. All-optical atomic clock based on coherent population trapping in 85Rb. Journal of the Optical Society of America B, volume 20, number 2, pages 273-279. © 2003 Optical Society of America (OSA). By permission.
  5. A. Shevchenko, M. Heiliö, T. Lindvall, A. Jaakkola, I. Tittonen, M. Kaivola, and T. Pfau. 2006. Trapping atoms on a transparent permanent-magnet atom chip. Physical Review A, volume 73, number 5, 051401(R), 4 pages. © 2006 American Physical Society (APS). By permission.

Errata of publication 2

Keywords: alkali metal, optical pumping, coherent population trapping, laser cooling

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Last update 2011-07-21