On the design of multipass dye laser amplifiers

We describe a universal method for designing multipass dye laser amplifiers typically pumped longitudinally by Q-switching high-energy pulses. The method is based on a set of normalized curves for the gain and on the experimental measurement of the amplifier noise. In this way, the method tries to maximize the gain and to reduce or control the losses in terms, of amplified spontaneous emission and reabsorption of the signal by the uninverted amplifying material. It has been tested to design and optimize a high-gain multipass amplifier for picosecond pulses. The realized system has a compact geometry and offers a gain of over 36 dB, with output pulse energy of 14 /spl mu/J and few megawatts of peak power.