We have developed a high-contrast, high-beam-quality Ti:sapphire amplifier producing pulses of 10 mJ in a single stage with 19% efficiency. The amplifier has a double-confocal multipass ring configuration that allows for a large mode volume by use of a collimated beam in the gain medium. We have designed the amplifier optics to correct for aberrations and for spatial gain narrowing. The compressed output beam has an M2 of 1.15. The use of an internal saturable absorber in the amplifier results in an intensity contrast of ~109. We anticipate this design will be useful to extend the multipass architecture to low-gain media and to still higher output energy.
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