The initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To... Show moreThe initial goal of this thesis was to demonstrate chaos in an open two-mirror resonator. We have designed a bifocal mirror that forms a resonator with an unstable inner and a stable outer part. To be able to distinguish phenomena unique for configuration from phenomena also present in conventional resonators, i.e., roughness-induced scattering and aberrations, the performance of a conventional stable resonator is investigated first. Roughness-induced scattering turns out to affect the cavity finesse as well as the average power throughput and produces mode coupling close to frequency-degenerate points. We demonstrate, furthermore, a method to accurately determine aberrations by measuring the Gouy phase of subsequent higher-order modes around frequency-degeneracy. The bifocal mirror is not fabricated by traditional grinding and polishing, but by diamond-machining. The eigenmodes of a resonator with one diamond-machined bifocal mirror turn out to be Laguerre-Gaussian. We demonstrate furthermore, the coupling of two resonators based on transmission spectra and patterns, and report on the ability of the configuration to fulfill the basic requirements to obtain chaos. Show less