High peak intensity characterization and optimization with a tight-focusing transmission parabola

A transmission parabola is a tight-focusing on-axis parabolic reflector that potentially enables ultra-high intensities when combined with high-power laser pulses. We propose a method to characterize the peak intensity generated with this optic by measuring the laser beam wavefront after reflection. The focused electromagnetic field and the corresponding peak intensity at the focal plane are calculated using the Stratton-Chu formulation. Without wavefront corrections, the measured intensity is strongly degraded due to alignment constraints and the quality of the manufactured optic. The intensity reached is at most 6% of the ideal case, where the beam wavefront is perfectly flat and aberration-free. However, we demonstrate that the focused peak intensity can be improved substantially by correcting the laser beam wavefront with a deformable mirror. An intensity approaching 70% of the ideal case is obtained, thus showing the relevance of the transmission parabola for high-intensity applications.