Most frequency-domain nonlinear-optical techniques measure only the magnitude of the Fourier transform of a temporal response and, hence, do not uniquely determine the response. We show that, for the commonly used response, h(t) = A exp(−t/τf) + B exp(−t/τs), where A ≡ α/τf and B ≡ (1 − α)/τs, the spectral line shape can always be fitted by two different values of α. A measurement of the optical Kerr transient of carbon disulfide illustrates this ambiguity. We also demonstrate a single-scan method that is free from such ambiguities. It involves adding coherent background with a nonzero quadrature-phase component, obtained simply by proper choice of probe wavelength.
© 1988 Optical Society of America
Original Manuscript: April 21, 1988
Manuscript Accepted: June 22, 1988
Published: October 1, 1988
Rick Trebino, Charles E. Barker, and Adnah G. Kostenbauder, "Rise–fall ambiguities and their removal from frequency-domain nonlinear-optical techniques," Opt. Lett. 13, 865-867 (1988)