As a continuation of two previous works, this work deals with the description of laser effect in a work substance constituted by three levels Microsystems. This project has the new issue of include the temporary dependency of the homogenous and isotropic optical pumping and to see its influence in the laser effect and its temporary profile. This situation is more interesting and nearer to the reality than the previous approach. This new approach was based on of the kinetic equations, the Einstein coefficients, and the resolution of differential equations by means of the SIMULINK® computer platform.