Implementation of a spherical double-plasma-mirror telescope for a multi-petawatt laser

High-power laser beamlines typically operate with fixed focusing conditions, limiting the focal spot size and peak intensity. To mitigate these restrictions, prior studies used curved plasma mirrors to adjust the F-number to a specific value. Here, a double-plasma-mirror (DPM) system including spherical optics in a telescope configuration is implemented to adapt the F-number of a multi-petawatt (PW) laser beam resulting in adjustability within a range of intensities. The system is optimized to minimize focal aberrations. A dedicated imaging system is used to evaluate focus quality and the DPM reflectivity at the multi-PW level. Temporal contrast enhancement of the reflected beam is additionally demonstrated, as evidenced by higher particle yield and proton kinetic energy from nanometer-thick foils, compared to results without DPMs. These findings enable multi-PW laser facilities to explore more extreme laser–plasma conditions that require ultra-high temporal contrast and intensity, while expanding their capabilities in intensity adjustment beyond designed specifications.