200-fs, 2-mJ pulses from 1-kHz Yb3+,Na+:CaF2 cryogenic amplifier

By merging Yb fiber oscillator and cryogenically cooled DPSS Yb³⁺,Na⁺: CaF₂ RA we have generated 195-fs 2-mJ pulses at a 1-kHz repetition rate. Amplification substantially beyond 2 mJ is feasible by improving the quality of surface polishing and AR coatings, as well as by optimizing the RA cavity. Spectral shaping of the seed is crucial for amplification of broad spectra and shows potential for attaining ~100-fs pulses.