Laser Frequency Upconversion in Pair Plasmas and in Novel Radiation Sources

Abstract

High intensity laser matter interactions are widely studied across a broad range of field and plasma parameters. These interactions produce unique physical behavior in a variety of applications. At high laser intensities, the dynamics of electrons in plasmas are significantly impacted by relativistic effects. This thesis describes the impact of relativistic particle motion in two cases, in which we purposefully manipulate the frequency of high intensity laser pulses in plasmas. In one case, we aim to produce detectable signatures of the combined collective effects resulting from the mix of plasma physics and quantum electrodynamics (QED). When QED driven electron-positron pair generation becomes significant, it may shift the frequency of a passing laser, but the laser frequency shift is suppressed by relativistic effects. To reduce this suppression, we determine optimal laser powers through numerical simulation for increasing the significance of the collective behavior of highly relativistic electrons and positrons. In the second case, we examine how the relativistic electron dynamics might resonantly produce high energy pulses beyond the ultraviolet. Resonant frequency upconversion can occur when laser intensities are high enough that the relativistic corrections are significant, but not dominant. Upconversion at high efficiencies would have high impact; it would allow new radiation sources since laser power is available at visible wavelengths but not at much shorter wavelengths. Mildly relativistic resonant upconversion is demonstrated numerically in two configurations in this thesis. We also identify how higher fidelity theoretical models might be employed to further develop these wave mixing schemes. Both problems build upon how classical plasma wave dynamics are changed at relativistic intensities.