Multipass Yb : KGW disk amplifier

We have investigated a multipass Yb : KGW disk amplifier based on the White cell configuration and pumped by a laser diode with a fibre output. It is shown that the three-mirror layout of the cell is three times more efficient than the four-mirror one, since the size and position of the signal beam on the surface of the active element do not depend on the cell number of passes. For a threemirror cell scheme, a small-signal gain G = 168 is obtained in experiments for a pump power of 360 W. The experimentally achieved gain of two such amplifiers arranged in series is 6 × 10⁴, which exceeds G 2 approximately two-fold.