The third harmonic optical applications such as optical phase conjugation, image processing, optical switching, and optical limiting in Photonics requires efficient nonlinear optical materials to be used with low power laser beams. During the last three decades, organic molecules have attracted the attention of many researchers due to their high nonlinear optical susceptibility and the possibility of tailoring their properties suitable to be used to protect optical detection components and devices such as human eyes and optical sensors, by controlling the output energy on the image plane below the desired level. Extensive studies have been performed and reported for the case of single crystals of organic molecules, organic molecules in liquid solutions, and organics and organometallics doped in various solid substances. One of the major benefits of organic optical materials is that they are usually much less costly and easier to process in device form than their inorganic materials. In this paper, an extensive literature survey on nonlinear optical materials is depicted. This includes review of organic nonlinear material research, materials for reverse saturation absorption, molecules for two-photon and multi-photon absorption, experimental techniques for nonlinear refraction, nonlinear absorption, optical limiting, and optical phase conjugation. Finally, the review includes the materials used in photonic devices, materials used for optical phase conjugation like nonresonant media and resonant media including absorbing liquid and solid materials, lasing gain media, metal vapors, and photorefractive materials
