Diffraction losses and mode structure of equivalent TEM_00 optical resonators

A general description is given which allows one to determine the diffraction losses and mode structure (intensity and phase distribution) of any arbitrary TEM(00) laser resonator lying in the stable region of the stability diagram. By means of equivalence] relations and adaption of the aperture size to the size of the undisturbed Gaussian beam it is possible to reduce the number of characterizing parameters to two: the adapting factor s, the product (g(1) . g(2)). Numerical results are shown. The intensity pattern of the far field is discussed.