Intense Laser-gas Interactions in Hollow-core Photonic Band-gap Fibers

Book excerpt: This dissertation presents an experimental investigation of intense laser field propagation in hollow-core photonic band-gap fibers (HC-PBGF). The primary aim of this work has been the production of coherent extreme ultraviolet radiation by high-harmonic generation in a gas-filled fiber. The geometric properties of HC-PBGFs have the potential for a dramatic reduction of the pulse energy previously required while the guiding principles should permit enhanced conversion by phase-matching the fundamental and harmonic waves. In this effort we also studied the glass contribution to the nonlinearity of these unique fibers showing the significant change that can occur by nanometer scale deviations in the core structure. We also, by careful mode matching to the fundamental fiber mode, demonstrated record-low coupling losses which allowed peak intensity transmission nearly an order of magnitude larger than previously observed. To avoid nonlinear effects while coupling into the high-harmonic generating fiber and absorption effects when coupling out xenon was introduced by a microchannel drilled through the side of the fiber with ultrafast-laser pulses. Though we were unable to observe high harmonic generation significant progress was made toward this goal including assembly and optimization of the vacuum chamber, construction of a gas-to-fiber delivery system and characterization of our detector by generating third harmonic in a continuous jet of xenon.