EXTRACTION EFFICIENCY OF SATURATED-GAIN HIGH-POWER DYE-LASER AMPLIFIERS - EFFECT OF NONLINEAR SIGNAL ABSORPTION

The effect of nonlinear signal absorption (NLSA) due to ground-state a bsorption and excited-state absorption in a transversely pumped high-p ower dye laser amplifier is theoretically examined with a one-dimensio nal steady-state model for a dye amplifier pumped by a copper vapor la ser. A well-approximated analytical expression for the extraction effi ciency is derived, from which the effect of NLSA in reducing the ampli fier efficiency can be appreciated immediately and can also be interpr eted in terms of certain characteristic lengths. The reduction in effi ciency due to NLSA is found to be largely independent of the pump powe r, provided that the signal power is increased linearly with the pump power to continue to saturate the amplifier gain and suppress amplifie d spontaneous emission.