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978-3-8439-1492-5, Reihe Physik
Ultrastable Laser Technologies and Atom-Light Interactions in Hollow Fibers
115 Seiten, Dissertation Universität Hamburg (2014), Softcover, A5
Atom interferometers promise to dramatically impact the field of inertial sensing. Since the phase shift in an atom interferometer scales with the square of the time T the matter wave spends in the interferometer, the key to tapping its full potential is the maximization of T which is achieved by putting the complete experimental setup into free fall, e.g. in a drop tower or sounding rocket. In the course of this dissertation, innovative laser system concepts were developed and thoroughly tested for this purpose. The main challenge in this context is the achievement of large mechanical and thermal stability in conjunction with maintenance-free operation in a tight space. To meet these demands, the optical systems presented here are based on Zerodur benefiting from its vanishing thermal expansion coefficient. In particular, single mode fiber couplers and collimators for quantum optics experiments which are based almost entirely on Zerodur were developed for the first time. With these complex fiber couplers and jointing techniques based on light curing adhesives, coupling efficiencies as high as 90% are achieved with a thermal sensitivity below 0.004 per K. An integrated system consisting of a diode laser and a Zerodur based frequency stabilization module has already passed all relevant qualification tests and will perform the first optical precision spectroscopy on a sub-orbital space flight.
One approach to further improve the performance of atom interferometers is to provide a guiding potential for the matter waves. A possible realization is a hollow fiber which supports a light mode providing an optical dipole potential for laser cooled atoms. In this work, the properties of an ensemble of cold Rb atoms in a hollow guide have been thoroughly characterized regarding its temperature and spatial extent. These quantities also determine the overlap of the atoms with a resonant light field in the fiber indicating that huge optical depths can be achieved. This is a result of the confinement of both atoms and light field to a transverse area close to the resonant scattering cross section. By a careful choice of fiber and an optimization of the trapping and detection system, an optical depth OD > 50 was measured in the system. These findings enable a new route towards nonlinear optics at low light levels using schemes based on electromagnetically induced transparency.