title: Analysis of the influence of spherical aberration from focusing through a dielectric slab in quantitative nonlinear optical susceptibility measurements using third-harmonic generation.
abstract: The third-order nonlinear susceptibility (chi(3)) can be measured quantitatively using third-harmonic generation (THG) from two different interfaces. For the first time it is demonstrated both in experiments and theory that the magnitude of the THG signals from the two interfaces is not only determined by material properties (refractive index and chi(3)), but also by optical aberrations. It is found that this method of chi(3) determination can be applied without additional correction factors only for focusing conditions with a numerical aperture (NA) </= 0.35. The implications for general application of THG in three-dimensional microscopy are discussed.
authors.forename: Rajesh S
authors.initials: RS
authors.lastname: Pillai
authors.forename: G J
authors.initials: GJ
authors.lastname: Brakenhoff
authors.forename: M
authors.initials: M
authors.lastname: Müller