Picosecond pulses from a cryogenically cooled, composite amplifier using Yb:YAG and Yb:GSAG

A cryogenic Yb amplifier using two laser materials, Gd3Sc2Al3O12 and Y3Al5O12 (YAG), has been used to obtain 70W average power at 5kHz pulse repetition frequency; the output was compressed to 1.6ps, compared with an input compressible to 1.4ps. The gain broadening obtained by combining two media enables shorter pulses than using Yb:YAG alone but retains the power-scaling advantages of cryogenic Yb:YAG.