Nonlinear chirp effect introduced by Kerr medium as optical switches in ultrafast time-resolved measurements

We report the study on the nonlinear chirp effect introduced by third-order nonlinear media used as Kerr gates in time- and spectrum-resolved measurements. In our experiment, white-light continuum generated by a femtosecond laser was used as the source pulse to examine the chirping introduced by a variety of Kerr media of various thicknesses as the optical gates, and the results were compared with that gated by a 1 mm beta-barium borate noncollinear optical parametric amplifier (NOPA). Remarkable nonlinear chirp was observed in the experiments when Kerr media compared with that measured by NOPA. The results indicate that the chirping introduced by Kerr media is significant and cannot be neglected, especially when the Kerr gate is employed in broadband femtosecond time-resolved ultraviolet-visible spectrum measurements.