title: Efficient free-space read-out of WGM lasers using circular micromirrors.
abstract: Lasing from whispering-gallery mode (WGM) resonators occurs omnidirectional in azimuthal plane. Most applications of WGM resonators require spectral analysis with off-chip detectors, where in-plane emission and beam divergence hinder efficient detection. We demonstrate redirecting WGM laser emission from all azimuthal angles using a circular micromirror placed around the cavity. By collecting reflections off the micromirror via free-space optics, read-out intensity improved by one order of magnitude. Blocking vertically emitted spontaneous emission and recording reflections off the micromirror only, signal-to-noise ratio improved from 4.6 dB to 15 dB. Our read-out concept may be applied to arbitrary WGM cavity geometries without deteriorating the cavity's quality factor.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wienhold
authors.forename: Sarah
authors.initials: S
authors.lastname: Kraemmer
authors.forename: Andreas
authors.initials: A
authors.lastname: Bacher
authors.forename: Heinz
authors.initials: H
authors.lastname: Kalt
authors.forename: Christian
authors.initials: C
authors.lastname: Koos
authors.forename: Sebastian
authors.initials: S
authors.lastname: Koeber
authors.forename: Timo
authors.initials: T
authors.lastname: Mappes