Z‐scan measurement of χ⁽³⁾ using top‐hat beams Available to Purchase

Z‐scan measurements of third‐order optical nonlinearities are usually carried out with Gaussian beams. Good quality Gaussian beams are not readily available, however, and to overcome this limitation, we analyze the Z‐scan experiment using top‐hat beams. A graphical method is developed which allows straightforward determination of the nonlinear refraction and absorption coefficients from experimental data. The advantage of using top‐hat beams is that it allows Z‐scan measurements using a wide variety of laser sources, including dye lasers. χ⁽³⁾ values obtained using Z‐scan measurements with top‐hat and Gaussian beams are compared for the liquid crystal 5CB (4‐cyano‐4′‐n‐pentybiphenyl).