Lesson 5 – Polarization I

As waves travel through a material, they vibrate in different directions with respect to the direction of travel. If light is coming at you, its waves may be vibrating up and down or side to side or even spinning in a spiral. This is call the polarization of light. The plane of light’s polarization must be initially defined by two lines, the surface normal and the direction the light propagates (two lines determine a plane). The polarization is therefore either parallel or p-polarized, which means it moves in the polarization plane, perpendicular or s-polarized, which means it moves perpendicular (or, in German, senkrecht) to the polarization plane or random/unpolarized, which means it is just as likely to move in the plane as it is to move perpendicular to the plane. Both p- and s-polarized light are known as states of linearly polarized light.

Optical elements may be constructed of polymer chains or fine wire grids to create linearly polarized light from unpolarized light. These optics have transmission axes that determine the linear polarization state of the transmitted light. If two linear polarizers are located in a beam of light and oriented so their transmission axes are crossed (at 90°), no light should transmit. If there exists a (clocked) angle between them, the amount of light varies as a function of this angle. This is known as Malus’ Law, which is an important relationship used to control the amount of light in an optical system.