Four-pass amplifier for the pulsed amplification of a narrow-bandwidth continuous-wave dye laser

We demonstrate a new type of four-pass dye laser amplifier that can reduce the possibility of parasitic oscillation between optical components used in the amplifier. Pumping the amplifier with a 5.6-mJ Q-switched doubled Nd:YAG laser output, we obtain high-peak-power pulsed output of an incident cw narrow-bandwidth dye laser beam with a power gain greater than 2 × 10^6. Subsequent amplification of the pulse with a conventional dye amplifier yields 42% energy efficiency. When a temporally stretched pumping pulse is used, the eventual bandwidth of the final output is measured to be 130 MHz.