Extreme ultraviolet frequency combs for precision measurement and strong-field physics

<p>The extreme ultraviolet (XUV) is a relatively unexplored spectral region for high-resolution\&nbsp;<span style="line-height: 1.6em;">laser spectroscopy. Many atomic and molecular systems of fundamental interest lie in wait of\&nbsp;</span><span style="line-height: 1.6em;">investigation, but the lack of highly coherent sources has forgone the ability to experiment. The XUV\&nbsp;</span><span style="line-height: 1.6em;">frequency comb offers exciting new frontiers for fundamental physics and measurement science by\&nbsp;</span><span style="line-height: 1.6em;">enabling direct and highly coherent laser access to the XUV. Prior to 2012, our group demonstrated\&nbsp;</span><span style="line-height: 1.6em;">the best levels of phase coherence in the XUV at the 10 MHz level and the most powerful XUV\&nbsp;</span><span style="line-height: 1.6em;">light source originating from high-order harmonic generation with powers of 220 W/harmonic.\&nbsp;</span><span style="line-height: 1.6em;">The work in this thesis improves upon both of these metrics demonstrating coherence at the 62.5\&nbsp;</span><span style="line-height: 1.6em;">mHz level (eight orders of magnitude improvement) and power levels approaching 1 mW/harmonic\&nbsp;</span><span style="line-height: 1.6em;">(five times improvement). Our work shows that it is possible to produce XUV light with coherence\&nbsp;</span><span style="line-height: 1.6em;">properties that rival that of visible light using the high-order harmonic generation process.</span></p>