title: Interferometric background reduction for femtosecond stimulated Raman scattering loss spectroscopy.
abstract: We present a purely optical method for background suppression in nonlinear spectroscopy based on linear interferometry. Employing an unbalanced Sagnac interferometer, an unprecedented background reduction of 17  dB over a broad bandwidth of 60  THz (2000  cm(-1)) is achieved and its application to femtosecond stimulated Raman scattering loss spectroscopy is demonstrated. Apart from raising the signal-to-background ratio in the measurement of the Raman intensity spectrum, this interferometric method grants access to the spectral phase of the resonant χ(3) contribution. The spectral phase becomes apparent as a dispersive lineshape and is reproduced numerically with a simple oscillator model.
authors.affiliation: Institute for Applied Physics, University of Münster, Corrensstr. 2, 48149 Münster, Germany. s.dobner@wwu.de
authors.forename: Sven
authors.initials: S
authors.lastname: Dobner
authors.forename: Carsten
authors.initials: C
authors.lastname: Cleff
authors.forename: Carsten
authors.initials: C
authors.lastname: Fallnich
authors.forename: Petra
authors.initials: P
authors.lastname: Groß