Introduction to Polarizers

Polarizers:

Polarizers are used to select a specific specialization of light. We can divide the polarizers into dichroic, reflective, and birefringent polarizers. Reflective polarizers basically transmit the desired polarization and simultaneously it reflects the rest. A common example is a wire grid polarizer, in which many thin wires are arranged parallel to each other. Light gets reflected back that is polarized along these wires, on the other hand, the light which is polarized in the perpendicular direction to these wires is transmitted. Other reflective polarizers use Brewster's angle. Brewster's angle is a specific angle of incidence within which only S-polarized light is reflected.

When the reflected beam is s-polarized and the beam which is transmitted becomes partially transmitted. A specific polarization of light is absorbed by Dichroic polarizers, transmitting the rest; modern nanoparticle polarizers are dichroic polarizers. Birefringent polarizers basically work on the basis of the refractive index of the polarization of the light. Different polarizations get refracted at different angles and can be used to select certain polarizations of light. The manufacturing of products optical mirrors requires incident polarization state of light and deep uv beam splitter cubes.

We can consider the unpolarized light as the combination of the p- and s- polarized light which keeps on varying. An ideal linear polarizer would transmit only one of the two linear polarizations, halving the initial unpolarized intensity.

Waveplates:

While the polarizers select some specific polarization of the light and discard the other polarizations, the ideal waveplate changes the polarization without forming any type of attenuation, deviation, or displacement in the beam. They do this by slowing (or delaying) a component of the polarization with respect to its orthogonal component. If the chosen waveplate is correct then it is able to convert any type of polarization state into a new polarization state and it is most commonly used to rotate the linear polarization, to perform the conversion of linearly polarized light into circularly polarized light, or vice-versa.

Application:

Control on the polarization can be used for a wide range of imaging applications. Over a light source, lens, or both a polarizer is placed to eliminate glare from light scattering, increase contrast, and eliminate hot spots from reflective objects. This ether gives us the more intense color or contrast as a result of helps us to better identify the surface defects or otherwise hidden structures.