Studies of Z-scan with "ring"-shaped beams

Summary form only given. A variety of experimental techniques for measuring nonlinear refractive and absorptive coefficients has been invented and developed during the last two decades. Here we concentrate on perhaps the simplest of these methods-the so-called Z-scan technique. By varying the position of a sample with respect to the focal plane of an input lens and detecting the energy transmitted through an aperture placed in the far field, one can determine the nonlinearly induced phase shift. In the absence of the aperture the nonlinear loss is measured. From these measurements, and knowledge of the underlying physics describing the nonlinear optical (NLO) response of the material, the nonlinear refractive index and absorption coefficient can be obtained.