Z-scan sensitivity enhancement using a binary diffractive optics

We report a theoretical study of the sensitivity enhancement of Z-scan technique, using a simple binary diffractive optical element. The latter is a phase aperture made from a transparent plate that has a circular relief introducing a π phase shift in the central region of the incident beam. We demonstrate that the phase aperture acts like a divergence multiplier allowing the Z-scan sensitivity to be increased by a factor of several hundred. PACS 42.25.Fx