Abstract
We start from the Helmholtz Equation, using Finite-Element Method to solve the stationary solutions,and construct the information in phase space using Husimi function . To get more direct physical insights, we map the phase space distribution on the Poincare Section of Surface,and give the handled phase space distribution physical interpretations . Finally, we use it to get more physical insights in some special systems. Based on these results,we study the stationary states in optical cavities .