Photonics: An Electromagnetic Approach introduces students to the field by means of a comprehensive integration of diverse explanations within a unified framework rooted in electromagnetic theory. This framework is designed to meet the needs of undergraduate (junior or senior) and graduate students, while also providing researchers with a moderately detailed description. The book strives to cover underlying physical photonics principles rather than focusing on actual devices and systems. It starts with the underlying physics in Maxwell’s equations. Many important features in photonics are covered as solutions of linear Maxwell’s equations, including reflection, refraction, interference, radiation, diffraction, optical waveguide, optical resonator, etc. Ray optics are introduced by considering the dimensionality of the interesting region. Resonant interactions between electromagnetic fields and media, including semiconductors, are explained classically or semi classically. Various dynamic characteristics of a laser are also discussed. Noise mechanisms in the detection and generation processes of optical radiation are also explained in detail. Fundamentals for nonlinear optical phenomena are explained by solving nonlinear wave equations both for elastic and inelastic nonlinearities.