ANALYSIS OF THE EZ SCAN MEASUREMENT TECHNIQUE

The Z scan experiment has been found to be a useful and simple techniq ue for the measurement of both the real and imaginary parts of the thi rd order (and higher orders) of the optical nonlinearity of a wide var iety of materials. The sensitivity of the technique, typically lambda/ 300, may be enhanced by over an order of magnitude in the EZ scan meth od by the substitution of field stop and collecting lens in place of t he usual aperture. In this paper such a detection scheme is analysed n umerically and a compact empirical expression for the nonlinearity in terms of the stop transmittance and the change in transmittance during the scan is derived.