In this chapter, we consider propagation of laser light in a linear region based on the wave optics, and the material dispersion: frequency dependence of the refractive index in complex expression. In Sect. 2.1, basic properties of a Gaussian beam are derived in paraxial wave approximation of an electromagnetic wave, with addition of the angular momentum of a laser beam including application to high field science and material processing. In Sect. 2.2, basic properties of the optical components used in high power lasers are described. In Sect. 2.3, we consider propagation of an ultrashort-duration laser pulse in a dispersive media, i.e., how the amplitude and phase change during propagation due to material dispersion. Also described are the dispersion properties of several optical components required to control propagation of ultrashort laser pulses. In Sect. 2.4, we briefly introduce relativity which is an extension of the electromagnetic theory and essential in high field science. The equations and constants are expressed in the International System of Units (SI Units). Vectors and tensors are indicated by bold letters.