Nonlinear Optical Activity (NLO) represents a pivotal domain within the realm of optics, which delves into the intricate comportment of light traversing a nonlinear medium, modulated by the presence of an electric field. This captivating phenomenon intertwines with two-photon absorption amidst electromagnetic fields, necessitating the meticulous scrutiny of material responses and hyperpolarizabilities to gauge the nonlinear retorts of substances when subjected to electric fields. The purview of NLO research encompasses the probing of photon activities, unravelling the behaviour of photons in nonlinear media, and employing sophisticated polarizable continuum models to portray light-matter interactions with utmost precision. Additionally, this erudite inquiry delves into the intrinsic attributes of light within homogenous dielectric continuous media, where the medium's characteristics exhibit homogeneity throughout its expanse. In essence, NLO endeavours to comprehensively elucidate the intricate comportment of light in nonlinear materials under the influence of electric fields, unravelling the enigmatic connections underlying two-photon absorption and hyperpolarizabilities. Such inquiry necessitates the meticulous exploration of photon activities, the application of sophisticated models to unravel the nuances of light-matter interactions, and a profound understanding of light's behaviour within uniform dielectric media.