title: Modulation-free frequency stabilization of external-cavity diode laser based on a phase-difference biased Sagnac interferometer.
abstract: We propose a modulation-free technique for frequency stabilization of an external-cavity diode laser (ECDL) by using a phase-difference biased Sagnac interferometer to produce dispersion spectroscopic error signals. A half-wave plate and a total internal reflection prism are inserted into the loop to provide a phase-difference bias between the clockwise and counterclockwise beams with perpendicular polarizations, instead of the previous method with misaligned optical paths. In the experiments, the frequency of the Littman-Metcalf configuration ECDL is locked at the transition of the Rb atomic vapor, and the frequency fluctuation is suppressed from 8 to less than 0.5 MHz peak to peak. It is shown that this scheme is simple, robust, low cost, and it shows promise for use in a variety of related applications.
authors.affiliation: Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Wei
authors.forename: Dijun
authors.initials: D
authors.lastname: Chen
authors.forename: Zujie
authors.initials: Z
authors.lastname: Fang
authors.forename: Haiwen
authors.initials: H
authors.lastname: Cai
authors.forename: Ronghui
authors.initials: R
authors.lastname: Qu