title: Coherent radio-frequency detection for narrowband direct comb spectroscopy.
abstract: We demonstrate a scheme for coherent narrowband direct optical frequency comb spectroscopy. An extended cavity diode laser is injection locked to a single mode of an optical frequency comb, frequency shifted, and used as a local oscillator to optically down-mix the interrogating comb on a fast photodetector. The high spectral coherence of the injection lock generates a microwave frequency comb at the output of the photodiode with very narrow features, enabling spectral information to be further down-mixed to RF frequencies, allowing optical transmittance and phase to be obtained using electronics commonly found in the lab. We demonstrate two methods for achieving this step: a serial mode-by-mode approach and a parallel dual-comb approach, with the Cs D1 transition at 894 nm as a test case.
authors.forename: James D
authors.initials: JD
authors.lastname: Anstie
authors.forename: Christopher
authors.initials: C
authors.lastname: Perrella
authors.forename: Philip S
authors.initials: PS
authors.lastname: Light
authors.forename: Andre N
authors.initials: AN
authors.lastname: Luiten