In the scenario, nonlinear optics is very important due the large number of applications such as optical limiting,image processing and nonlinear devices etc. There are considerable research efforts to study the mechanisms of optical power limiting, synthesize new materials and develop devices with advanced properties. An optical limiter is a device that strongly attenuates optical beam to a threshold level at high intensity while exhibits linear transmittance at low intensity. Such devices are used for protecting human eyes and optical sensors from damage due to exposure to intense radiation. The search for efficient optical limiters has lead to the study of various materials. This book is dealing with the problem of new materials and characterize them using Z-scan technique, it will be very helpful for the researchers and students who are working in the area of Nonlinear Optics.