Distortion-compensated multifocusing of ultrashort pulse beams using cascade optical system

We report a cascade optical system for multifocusing ultrashort pulse beams, particularly sub-50-fs pulses. System achromaticity is key to simultaneous compensation of the spatio-temporal pulse distortions. In this system, diffractive and refractive subsystems are optically coupled in cascade to correct chromatic aberrations, which are the primary cause of pulse distortion. We design a prototype system by applying achromatic conditions derived from an ABCD matrix analysis. The designed system is then evaluated using 20-fs pulses, by characterizing the transmitted pulses in terms of beam width and pulse duration; hence, the proposed distortion compensation scheme is validated. This pulse delivery system enables damage-free and high-throughput materials processing using ultrashort pulses.