Nonlinear optics is a branch of optics that studies how light interacts with matter in a way that is not directly proportional to the light's intensity. In typical linear optical processes, the response of a material to light is predictable and consistent. However, in nonlinear optics, changes in the material's properties can occur at high light intensities, leading to phenomena such as frequency doubling, self-focusing, and solitons. These nonlinear effects enable various applications, including the generation of new wavelengths of light and the development of advanced imaging techniques. Nonlinear optics plays a crucial role in technologies like lasers, fiber optics, and optical communication, enhancing our ability to manipulate and utilize light in innovative ways.