Inorganic thin film anisotropy studied by second-harmonic generation

Second-harmonic generation (SHG) was used to determine the dominant isotropic and anisotropic components of the effective second-order susceptibility tensor in a homogeneous, broadband, anti-reflection coating. The nonlinear optical signal was predominantly due to the isotropic components χyzy(2) and χzzz(2) under oblique angle of incidence. At normal incidence anisotropic contributions could also be identified but were found to be at least one order of magnitude less than the isotropic components. Due to the high degree of isotropy of this film and the accuracy in determining its χ(2) values, we propose its use as a reliable standard in the field of SHG from surfaces and interfaces.