The effect of thermally induced gain gradients in solid state lasers

A dependence of the small-signal gain in solid-state lasers on the thermal loading is calculated. An average thermal power dependent gain reduction factor, eta /sub g/(Q), is defined in terms of the temperature coefficients of the laser gain curve, and the thermal conductivity of the laser rod. eta /sub g/(Q) arises from the shifts in the laser gain curve associated with the temperature gradients caused by optical pumping, and reduces the small-signal gain. The calculation of eta /sub g/(Q) for the specific cases of Nd:YAG and Nd;Cr:GSGG lasers indicates a reduction in the small-signal gain, from this mechanism alone, of 20-30% at high average power (200 W-cm/sup -3/, thermal).<
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