title: Modified negative-branch confocal unstable resonator.
abstract: A new type of unstable resonator, suitable for a laser with a large medium cross section and a small or median output coupling, is presented. The resonator configuration, a modification of a negative-branch confocal unstable resonator, is numerically investigated. The basis of the theory is the Fresnel-Kirchhoff integral equation, and the calculations describe a passive resonator. With respect to output mirror tilting, the calculations confirm that the modified negative-branch confocal unstable resonator is less sensitive to mirror misalignments than the conventional negative-branch confocal unstable resonator. Furthermore, the modified resonator improves the beam quality in comparison with the conventional unstable resonator.
authors.affiliation: German Aerospace Center, Institute of Technical Physics, Stuttgart, Germany. Thomas.Hall@dlr.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Hall
authors.forename: Frank
authors.initials: F
authors.lastname: Duschek
authors.forename: Karin M
authors.initials: KM
authors.lastname: Grünewald
authors.forename: Jürgen
authors.initials: J
authors.lastname: Handke