The work includes the development of a program in an advanced – programming
language. to solve two none linear related partial differential equation that form a
mathematical model that describes the dynamic status of laser ,so that we can study the
properties of radiation density through this type the related program ,as well as the
population inversion inside the homogeneous medium of laser . We have studied the
strength f the out put power as well as the population inversion in the case of pulse –
working of the solid state laser Nd:YAG and the population inversion change as a function
of the diameter and length of the effective medium of laser .
