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/τƒ) + B exp(-t/τs),where A≡ α/τƒ 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 ambiguitv. We also demonstrate a single-scan method that is free from such ambiguities. It involves adding coherent background with a nonzero quadrature-phase wavelength.
© 1988 Optical Society of America
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)