The various subproblems for DH lasers such as field distribution, carrier profile, and temperature distribution are investigated. Solutions to these problems are obtained either analytically or by precise numerical methods. By combining the subproblems, a detailed model for the static properties is obtained. The model is applicable as well below as above threshold and properties of interest in the application of DH lasers such as threshold current, field distribution at a given current, and light current characteristics can be found. Nonlinear characteristics are found even for ideal symmetrical lasers. These "kinks" are associated with higher order modes and appear at relatively high values of the optical power.