We report the theoretical investigation of the Z-scan technique for characterizing the instantaneous Kerr nonlinearity of an optically thin multiphoton absorber. Based on the Huygens–Fresnel diffraction integral method, we study the characteristics of the closed-aperture Z-scan traces. Most importantly, we present the analytical formulae of the closed-aperture Z-scan transmittance with simultaneous Kerr effect and n-photon absorption. Besides, we demonstrate that the determination of the third-order nonlinear refractive index in multiphoton absorbers becomes timesaving yet unambiguously by the presented theory.
© 2010 Optical Society of America
Original Manuscript: July 2, 2010
Revised Manuscript: September 22, 2010
Manuscript Accepted: September 29, 2010
Published: October 27, 2010
Bing Gu, Kai Lou, Jing Chen, Hui-Tian Wang, and Wei Ji, "Determination of the nonlinear refractive index in multiphoton absorbers by Z-scan measurements," J. Opt. Soc. Am. B 27, 2438-2442 (2010)