![]() There are many optical components that utilize the concept of Brewster’s angle for useful applications. For p-polarization, the reflectivity vanishes at the Brewster angle (in this case, ~56°) while reflectivity for s-polarization steadily increases with increasing incidence angle. The polarization extinction ratio $ \left( \text $ can also be expressed in decibels, which is calculated using:įigure 2: Fresnel reflectivity at an air-glass optical interface vs. In addition, losses in the resonator, from the inclusion of a Brewster plate or a slight misalignment of any other optical components involved, can be responsible for changes in polarized laser emissions. With the absence of polarization-selection optics, such as polarizers and waveplates (also called retarders), light would be unpolarized and unsuitable for certain applications. Stimulated emission photons will be emitted in the same polarization state as that of the pump photons. ![]() Inside this medium, emission is stimulated by incoming pump photons. A laser gain medium may be polarization-dependent, as is the case with some anisotropic laser crystals and semiconductor optical amplifiers. "Anisotropic" refers to properties whose values vary in different directions. The state of a laser's polarization is determined by several anisotropic mechanisms of either the laser gain media or the resonator. The basic principles of polarization are covered in our Introduction to Polarization application note, but this guide dives into the specific application of those concepts to laser applications. While most laser sources are linearly polarized, other classifications of polarization can also be generated, such as circular, elliptical, and radial polarization. ![]() Understanding the polarization of laser light is important for many applications, as polarization impacts reflectance, the focus of laser beams, and other optical behaviors that affect end applications of the laser. ![]() Laser sources, on the other hand, are often linearly polarized. Many light sources including sunlight, halogen lighting, and LED spotlights are considered unpolarized because the orientation of their electric fields fluctuates randomly in time. The orientation of the electric field in the light wave is described by the light's polarization. Light can be understood as a transverse electromagnetic wave composed of oscillating electric and magnetic fields. ![]()
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