Experiments with Ultracold Fermi gases : Quantum Degeneracy of Potassium-40 and All-solid-state Laser Sources for Lithium
Norman Kretzschmar (LKB)

This thesis presents novel techniques for the experimental study of ultracold quantum gases of fermionic lithium and potassium atoms.
In the first part of this thesis, we describe the design and characterization of the new components of our experimental apparatus capable of trapping and cooling simultaneously 6Li and 40K atoms to ultracold temperatures. We report on a novel sub-Doppler cooling mechanism, operating on the D1 line transition of alkali atoms, for laser cooling of lithium and potassium. The measured phase space densities after this molasses phase are on the order of 1e-4 for both 6Li and 40K. We present the forced evaporative cooling of 40K atoms, starting in an optically plugged magnetic quadrupole trap and continuing in an optical dipole trap. In this context, we report on the production of a quantum degenerate Fermi gas of 1.5e5 atoms 40K in a crossed dipole trap with T/TF = 0.17, paving the way for the study of strongly interacting superfluids of 40K.
In the second part of this thesis, we present a narrow-linewidth, all-solid-state laser source, emitting 5.2 W in the vicinity of the lithium D-line transitions at 671 nm. The source is based on a diode-end-pumped unidirectional ring laser operating on the 1342 nm transition of Nd:YVO4, capable of producing 6.5 W of single-mode light delivered in a diffraction-limited beam. We report on three different approaches for second-haromonic generation of its output beam, namely by employing an enhancement cavity containing a ppKTP crystal, intracavity frequency doubling and a ppZnO:LN waveguide structure.