title: Z-scan theory for material with two- and three-photon absorption.
abstract: We present a theoretical study on the Z-scan characteristics of thin nonlinear optical media with simultaneous two- and three-photon absorption, a situation that exists, for example, in polydiacetylenes. With the introduction of a coupling function between two- and three-photon absorption, we find a quasi-analytic expression for open aperture Z-scan traces. We make a comparison of the analytic solutions with numerical solutions in detail, showing that they are in good agreement. This theoretical result allows us to easily identify and determine simultaneously the two- and three-photon absorption coefficients from the open aperture Z-scan traces.
authors.forename: Bing
authors.initials: B
authors.lastname: Gu
authors.forename: Jin
authors.initials: J
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Ya-Xian
authors.initials: YX
authors.lastname: Fan
authors.forename: Jianping
authors.initials: J
authors.lastname: Ding
authors.forename: Hui-Tian
authors.initials: HT
authors.lastname: Wang