Lyman-alpha sources for laser cooling of antihydrogen

For future laser cooling of anti-hydrogen as well as quantum information processing with Rydberg-ions, there is a need for a strong continuous vacuum ultraviolet (VUV) laser source in the region of 121-123 nm. Non-degenerate four-wave mixing (FWM) in metal vapors is a well-established method for VUV generation. A power enhancement, compared to the use of focussed beams, can be achieved with an elongated interaction region of the fundamental beams, by confining the light in a vapor filled hollow core fiber. A study of possible phase-matching scenarios and their associated VUV efficiencies is presented, considering dispersion and losses due to the medium as well as the fiber. A gain of up to three orders of magnitude in the output power should be feasible. Sufficiently high mercury vapor densities within the fiber are confirmed via absorption spectroscopy on the 61S - 63P transition in mercury transverse through the fiber. Within the hollow core fiber, nonlinear processes like two-photon induced lasing could be observed, and we demonstrate the first cw VUV generation in a metal vapor filled hollow fiber. The attained mixing efficiencies are already comparable to those achievable with focussed beams, although perfect phasematching of the process was so far not possible. Furthermore, the investigation of the 61S-71S two-photon transition in mercury led to an evidence of a to date experimentally unobserved light-induced drift, based on multi-photon excitation.