Nonlinear absorber characteristics and their effects on discrimination amplifiers

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Abstract
In an effort to suppress the background intensity surrounding short laser pulses we have investigated the behavior of various discrimination amplifiers. These amplifiers are made up of a sequence of bleachable dyes and amplifiers having an over-all small-signal gain below unity and a large-signal gain above unity. The characteristics of such amplifiers depend strongly on the dye transmission which is itself a function of the particular spatial and temporal profile of the laser pulse propagated through it. This characteristic was investigated experimentally and theoretically. We found 84% transmission at 100 times the saturation intensity of a dye of initial transmission T0=0.2. As a consequence, typical experimental pulse profiles reduce the background suppression efficiency of discrimination amplifiers considerably. However, background suppression of over 2000 is attainable.