Cryogenically cooled, 149 W, Q-switched, Yb:LiYF4 laser.

We demonstrate a 149 W Yb:LiYF(4) laser with diffraction-limited beam quality at 995 nm. The laser, Q-switched at 10 kHz pulse repetition frequency, produces linearly polarized 52 ns pulses with a slope efficiency of 73%. The combination of cryogenic cooling and a low (3.5%) quantum defect results in minimal thermo-optic effects and high thermal efficiency. The measured heat load to the cryogen is 0.15 W per watt of output. These results show the potential for significant power scaling of Q-switched Yb:YLF lasers with excellent beam quality.

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 70 W average power at 5 kHz pulse repetition frequency; the output was compressed to 1.6 ps, compared with an input compressible to 1.4 ps. 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.

165-W cryogenically cooled Yb:YAG laser.

Thermo-optic distortions often limit the beam quality and power scaling of high-average-power lasers. Cryogenically cooled Yb:YAG is used to efficiently generate 165 W of near-diffraction-limited beam from a power oscillator with negligible thermo-optic effects. End pumped with 215 W of incident pump power from two diode modules, the laser has an optical-optical efficiency of 76%, a slope efficiency of 85%, and an M2 value of 1.02.