crossedpolarized

Crossed polarization, or crossed-polarized configuration, refers to the arrangement of two polarizing optical elements with their transmission axes oriented at right angles (90 degrees) to each other. In this setup, light that has been polarized by the first filter is supposed to be blocked by the second, so ideally no light is transmitted.

The behavior of light in a crossed-polarized system is described by Malus's law: the transmitted intensity I = I0 cos^2(theta), where theta is the angle between the transmission axes. For theta = 90 degrees, I is zero in an ideal, perfectly polarizing system. In practice, real polarizers are not perfect, so a small amount of light leaks through due to imperfect polarization, scattering, and other non-idealities. The remaining transmission is quantified by the extinction ratio, a measure of how well the system suppresses the orthogonal polarization.

Crossed polarizers have several key applications. In polarized light microscopy, a pair of crossed polarizers reveals birefringent materials, producing contrast and interference colors that indicate stress, composition, or crystal structure. In liquid-crystal displays, a pair of orthogonal polarizers is used in combination with a birefringent liquid-crystal layer to modulate brightness. In photography and optics, crossed polarizers are used to suppress glare by aligning a polarizer with the polarization of reflected light and analyzers in specific configurations. They are also used in security, materials testing, and scientific demonstrations to illustrate polarization concepts.

In summary, crossed polarization describes a perpendicular polarizer arrangement that ideally blocks light, with real-world applications spanning microscopy, displays, and optical testing.