Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 50: Poster Ultrakalte Atome
Q 50.16: Poster
Thursday, March 13, 2008, 16:30–19:00, Poster C2
Fringe-free imaging of BEC with spatially incoherent light — •Jochen Kronjäger1, Lars Neumann1, Christoph Becker1, Kai Bongs2, and Klaus Sengstock1 — 1Institut für Laser-Physik, Universität Hamburg — 2Midlands Centre for Ultracold Atoms, University of Birmingham
Imaging techniques of cold atomic gases, e.g. alkali Bose-Einstein condensates, critically rely on one atomic absorption line with a width of a few MHz typically. Laser light from the same source used for e.g. Doppler cooling naturally provides the highly concentrated spectral power density needed for efficient absorption or phase contrast imaging. The drawback of using laser illumination in any application is interference fringes, originating from diffraction at optical apertures or dust particles and multiple reflections on optical surfaces in the light path.
We have developed and tested an approach to neutralize these unwanted artefacts which is based on laser light scattered from an opaque fluid. In a simplified view, random scattering destroys the spatial coherence of the beam, while preserving its spectral narrowness. A more refined approach based on the properties of laser speckle allows to quantitatively analyze our setup and demonstrates its fitness for the purpose of fringe reduction.