High-average-power, high-repetition-rates picosecond-pulsed regenerative ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser amplifiers were developed. The architecture used in the amplifiers, which are named as thin-rod, has a unique cooling scheme like slab lasers and also has a unique pumping scheme like photonic crystal fiber lasers, is suitable for high-average power Ytterbium lasers. This architecture also has high gain characteristics which is appropriate for the regenerative spectral and pulse shaping on high-repetition-rate, ultrashort-pulse amplifications.
High-efficiency cavity-dumped ytterbium-doped yttrium aluminum garnet (Yb:YAG) laser was developed. Although the
high quantum efficiency of ytterbium-doped laser materials is appropriate for high-efficiency laser oscillation, the
efficiency is decreased by their quasi-three/four laser natures. High gain operation by high intensity pumping is suitable
for high efficiency oscillation on the quasi-three/four lasers without extremely low temperature cooling. In our group,
highest efficiency oscillations for continuous wave, nanosecond to picosecond pulse lasers were achieved at room
temperature by the high gain operation in which pump intensities were beyond 100 kW/cm<sup>2</sup>.