title: Laser-frequency locking to a whispering-gallery-mode cavity by spatial interference of scattered light.
abstract: We present a simple and effective method for frequency locking a laser source to a free-space-coupled whispering-gallery-mode cavity. The scheme relies on the interference of spatial modes contained in the light scattered by the cavity, where low- and high-order modes are simultaneously excited. A dispersion-shaped signal proportional to the imaginary component of the resonant optical field is simply generated by spatial filtering of the scattered light. Locking of a diode laser to the equatorial modes of a liquid droplet resonator is demonstrated using this scheme, and its performance is compared to the Pound-Drever-Hall technique. This new approach makes laser-frequency locking straightforward and shows a number of advantages, including robustness, low cost, and no need for sophisticated optical and electronic components.
authors.forename: R
authors.initials: R
authors.lastname: Zullo
authors.forename: A
authors.initials: A
authors.lastname: Giorgini
authors.forename: S
authors.initials: S
authors.lastname: Avino
authors.forename: P
authors.initials: P
authors.lastname: Malara
authors.forename: P
authors.initials: P
authors.lastname: De Natale
authors.forename: G
authors.initials: G
authors.lastname: Gagliardi