title: Transverse mode tailoring in a quasi-imaging high-finesse femtosecond enhancement cavity.
abstract: We demonstrate a high-finesse femtosecond enhancement cavity with an on-axis obstacle. By inserting a wire with a width of 5% of the fundamental mode diameter, the finesse of F = 3400 is only slightly reduced to F = 3000. The low loss is due to the degeneracy of transverse modes, which allows for exciting a circulating field distribution avoiding the obstacle. We call this condition quasi-imaging. The concept could be used for output coupling of intracavity-generated higher-order harmonics through an on-axis opening in one of the cavity mirrors.
authors.affiliation: Lehrstuhl für Lasertechnik LLT, RWTH Aachen University, Steinbachstr. 15, 52074 Aachen, Germany. johannes.weitenberg@ilt.fraunhofer.de
authors.forename: Johannes
authors.initials: J
authors.lastname: Weitenberg
authors.forename: Peter
authors.initials: P
authors.lastname: Russbüldt
authors.forename: Tino
authors.initials: T
authors.lastname: Eidam
authors.forename: Ioachim
authors.initials: I
authors.lastname: Pupeza