Theoretical investigation of the off-axis z-scan technique for nonlinear optical refraction measurement.

The theoretical investigation of the off-axis z-scan technique for the measurement of nonlinear optical refraction in materials is presented. The normalized transmittance is calculated for different aperture radii and positions. The dependence of both the normalized transmittance amplitude (DeltaT(pv)) and the distance between maximum and minimum (Deltaz(pv)) on the aperture radius is analyzed. A condition for the applicability of the pinhole approximation is given.