A resonator with an internal lens can be characterized by its equivalent g-parameters which give the regions of stability if the lens has variable focal length. However, other properties are not given by this equivalence and have to be investigated by means of the resonator matrix method. Beam diameter, divergence angle, number of transversal modes, positions of beam waists, stability, and the correlations of these parameters with position and focal length of the internal lens are discussed. Regions of low sensitivity to variations of the focal length are evaluated and compared with experimental results. For some special resonator configurations numerical results are presented.

The effect of mirror misalignment of spherical resonators is investigated experimentally and compared to first-order perturbation theory. An expression D is derived, which characterizes the misalignment sensitivity of any spherical resonator. It is proved experimentally that this misalignment sensitivity depends on the effective resonator length L and the gi parameters only.

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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.

We describe a simple system for the generation of tunable picosecond pulses in the millijoule range.The system consists of an active /passive mode -locked Nd:YAG pump laser which emits a single pulse, and the dye laser part which employs a single mode short cavity dye laser and two double pumped amplifiers.