Overcoming energy limitation in post-compression of picosecond pulses by free beam propagation in air and temporal pulse splitting and recombining

Abstract

Cryogenically cooled diode-pumped Yb:YAG has been demonstrated to efficientlygenerate pulses of >1 J energy and several picoseconds duration at a kilohertz repetition rate.Pulse broadening and post-compression techniques capable of operating at these high pulseenergies will expand the use of these lasers in applications requiring shorter pulses. Towards thisgoal, we demonstrate the post-compression of 5.5 ps pulses with energy in the 0.1 J range byspectral broadening of self-collimated large area beams in air. In proof-of-principle experiments,pulses of 65 mJ energy from a cryogenically cooled Yb:YAG laser were compressed to 1.1 psafter 65m propagation in a compact setup in which the beam was folded using flat mirrors.Further energy scaling was demonstrated by combining this spectral broadening technique withtemporal pulse splitting and recombining. 120 mJ pulses were split into two pulses and coherentlyrecombined with 85% efficiency after 50m of propagation in air to yield 1.4 ps pulses.