Heidi Lundgaard Sørensen
A thesis submitted December 2015 for the degree of Doctor of Philosophy and defended January 21, 2016.
The PhD School of Science
Faculty of Science
Niels Bohr Institute, Quantum Optics, University of Copenhagen
Eugene S. Polzik
Jörg H. Müller
A WAVEGUIDE P LAT FORM FOR COL L ECT IVE L IGHT-ATOM INT ERACT ION
In this work a tapered optical fiber is studied as a waveguide platform for efficient collective light-atom interaction. We present an allcomputer controlled heat-and-pull setup with which a standard optical fiber can reproducible be tapered down to sub-micron waist size.
The resulting fiber shape is compared against a prediction derived from a numerical model build upon an easy experimental calibration of the viscosity profile within the heater. Very good agreement between the modeled and measured fiber shape is found.
We next study the coherent back-scattering off atoms confined as two one-dimensional strings in the evanescent field of a tapered optical fiber. By applying a near-resonant standing wave field, the atoms are arranged into a periodic Bragg structure in close analogy to a photo-refractive medium with a refractive index grating. We observe more than 10% power reflection off about 1000 structured atoms, corresponding to an enhancement of two orders of magnitude when compared to reflections off an unstructured atomic ensemble.