Abstract
We are concerned with the study of the system of coupled of motion for a system of two-level atoms interacting with a single-mode field in the laser cavity on resonance. The passage from the equation of motion to the Lorenz equations is established. Some theoretical aspects of the slowly time-varying phenomena in cavities are discussed and the linear stability analysis is presented. A new approach to solve these nonlinear coupled differential equations is explored and its generalization to the case of variable coefficients is performed.