title: Improved sensitivity of intensity-modulated spectroscopy using correlative signal processing.
abstract: Frequency-modulation (FM) spectroscopy is known to be a sensitive spectroscopic technique capable of accurately measuring the frequency dependence of the absorption and index of refraction of narrow spectral features. The absorption and index of refraction are coupled by a form of the Kramers-Kronig (K-K) relations, and both components provide information about the spectral feature. In this Letter, we propose a processing technique based on fitting the data to a complex signal model derived from the K-K relation. By using this complex constraint and only processing a single quadrature, our model predicts significant improvement in the minimum detectable absorption compared with conventional FM spectroscopy.
authors.affiliation: Electrical and Computer Engineering Department, University of California, San Diego, La Jolla, California, USA. vataie@ucsd.edu
authors.forename: Vahid
authors.initials: V
authors.lastname: Ataie
authors.forename: George
authors.initials: G
authors.lastname: Papen