Deformation of the focal spot of an ultrashort high-power laser pulse due to chromatic aberration by a beam expander

Abstract

The spatial and temporal intensity distribution of a focal spot is investigated when an ultrashort high-power laser pulse is focused with chromatic aberration induced by a simple beam expander. The chromatic aberration due to the simple beam expander is calculated and measured for the 100-TW Ti:sapphire laser system at the Advanced Photonics Research Institute. The chromatic aberration reduces the peak intensity of the focal spot and broadens the temporal profile of the focal spot. By calculating the spatial and temporal intensity distribution of the focal spot, we can accurately estimate the peak intensity of the focal spot for the ultrashort high-power laser pulse with chromatic aberration. To avoid chromatic aberration, an air-spaced achromatic beam expander is designed and characterized for application to the ultrashort high-power laser system.