Gaussian decomposition is used as a theoretical infrastructure with which <i>Z</i>-scan experiments are analyzed. This procedure is extended here to the interesting, from a practical point of view, case in which the laser beam used is not perfectly Gaussian. We follow a perturbative approach to obtain the far-field pattern of the beam after the beam passes through a nonlinear sample. The procedure is based on the decomposition of the electric field at the exit plane of the sample to a linear combination of Hermite–Gaussian functions. To a first-order approximation, each mode of the incident beam is decomposed to a linear combination of different-order modes that do not exceed the order of the original mode. Finally, the effects of the simultaneous presence of first and higher-order refractive nonlinearities or first-order refractive nonlinearity and nonlinear absorption are studied.
© 2003 Optical Society of America
(000.3860) General : Mathematical methods in physics
(140.3300) Lasers and laser optics : Laser beam shaping
(260.5950) Physical optics : Self-focusing
(350.5500) Other areas of optics : Propagation
G. Tsigaridas, M. Fakis, I. Polyzos, M. Tsibouri, P. Persephonis, and V. Giannetas, "Z -scan analysis for near-Gaussian beams through Hermite–Gaussian decomposition," J. Opt. Soc. Am. B 20, 670-676 (2003)