Diffractive Plasma Optics via Ionization for the Generation and Control of High-Power Laser Pulses

The light intensity that can be produced by large lasers is limited by optical damage. Replacing standard optical components with plasma, which tolerates far higher intensity, provides a route to compact ultra-high-power lasers. However, creating plasma optics with adequate quality has proven difficult, and experimental efficiencies are often much lower than theoretical predictions. Diffractive ionization optics are a specific type of plasma optic that use interfering pump beams to generate wavelength-scale modulations of plasma density that control a delayed probe laser pulse. Because they average over a volume and avoid instabilities, diffractive optics should be more robust to plasma imperfections and inhomogeneity than alternative plasma approaches. Using two separate experimental approaches, avalanche-ionization gratings produced by 100-ps pump pulses and field-ionization gratings driven by femtosecond pulses, we have demonstrated substantially improved diffraction efficiency of intense femtosecond pulses from ionization gratings. For avalanche gratings, up to 60% of the incident probe energy can be redirected into a stable, focusable beam [1]. We have shown that the evolution of the grating affects the diffracted beam and directly measured the plasma fringes that make up the fine-scale grating structure. These experiments have produced ionization structures with plasma density and optical quality near what is required for diffractive plasma lenses [2] and compressors [3], suggesting the addition of ionization optics to the component toolkit for compact high-power laser systems.