title: External-cavity diode laser in second-order Littrow configuration.
abstract: In this Letter, we propose and demonstrate an external-cavity diode laser in second-order Littrow configuration. This topology utilizes a low-efficiency diffraction grating to establish a high-finesse external cavity, strong optical feedback, a high polarization discrimination, and a circular TEM00 output mode. In our proof-of-concept experiment, we realized a cavity with a finesse of 1855, being, to the best of our knowledge, the highest value ever reported for a three-port-grating-coupled cavity. With optical feedback, the laser threshold of the laser diode employed was reduced by a factor of 4.
authors.affiliation: Max Planck Institute for Gravitational Physics, Albert Einstein Institute, and Institut für Gravitationsphysik, Leibniz Universität Hannover, Hannover, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Britzger
authors.forename: A
authors.initials: A
authors.lastname: Khalaidovski
authors.forename: B
authors.initials: B
authors.lastname: Hemb
authors.forename: E-B
authors.initials: EB
authors.lastname: Kley
authors.forename: F
authors.initials: F
authors.lastname: Brückner
authors.forename: R-H
authors.initials: RH
authors.lastname: Rinkleff
authors.forename: K
authors.initials: K
authors.lastname: Danzmann
authors.forename: R
authors.initials: R
authors.lastname: Schnabel