title: Nonlinear refraction spectroscopy in resonance with laser lines in solids.
abstract: We report a simple extension of the Z-scan technique that permits a spectral line-shape measurement of the real and the imaginary parts of n(2) . In this technique the sample is placed at the peak position of the usual Z-scan curve while the laser frequency is scanned. We employed this method to investigate the nonlinear susceptibility of the R lines of ruby and alexandrite, using a cw dye laser. This susceptibility can be explained by the resonant interaction and by a nonresonant contribution that is due to the difference in polarizability between Cr(3+) excited and ground states. For ruby, the nonresonant contribution to the technique is 1 order of magnitude larger than the resonant contribution. However, for alexandrite both contributions are comparable, and their interference leads to a shift between n(2)(?) and n(2)(??) spectra that is not observed in ruby.
authors.forename: S M
authors.initials: SM
authors.lastname: Lima
authors.forename: H
authors.initials: H
authors.lastname: Jiao
authors.forename: L A O
authors.initials: LA
authors.lastname: Nunes
authors.forename: T
authors.initials: T
authors.lastname: Catunda