Wire Grid Polarizers


Optometrics Manufactures Wire Grid Polarizers Using Two Methods:

  1. Ruling precisely spaced grooves directly into a highly polished CaF2 or ZnSe substrate and then aluminizing the substrate, allowing the use of the polarizers with relatively high power lasers.
  2. Holographic method of producing grooves, allowing the use of a wider array of infrared materials such as BaF2, KRS-5 and Germanium as well as the traditional CaF2 and ZnSe. The finer grid spacing improves short wavelength performance.
Optometrics manufactures ruled wire grid polarizers on calcium fluoride (CaF2) and zinc selenide substrates (ZnSe), together covering a wavelength range from 2 to 20 microns and holographic wire grid polarizers on ZnSe, CaF2, BaF2 and KRS-5 and Germanium covering a wavelength region from 2 to 30 microns. Wire grid polarizers are commonly used to polarize radiation from an unpolarized molecular laser, attenuate radiation from a polarized laser or, using two in series, to both polarize and attenuate a laser beam. A second polarizer can be inserted in the reflected beam for applications requiring a polarizing beam splitter. Wire grid polarizers are also used in reflectance accessories for dispersive and FT-IR spectrophotometers. Applications include the investigation of metal surfaces and crystal structures at grazing incidence, where polarization of the incident radiation is required.

A wire grid polarizer transmits radiation when the “E” vector is perpendicular to the wire (E ). Radiation with the “E” vector parallel to the wire (E II) is reflected. Due to surface reflections, the reflected beam contains both polarizations.

The extinction ratio of a polarizer is a measure of its ability to attenuate a plane polarized beam. Two principle transmissions are necessary to calculate an extinction ratio, T1 and T2. Assuming a perfectly plane polarized beam, T1 is defined as the maximum transmission for which the polarizer can be oriented. Minimum transmission (T2) is the transmission through the polarizer when it is rotated 90 degrees from T1. The extinction ratio is given as E = T2/T1 and expressed as a decimal or percentage. The inverse of E, expressed as a ratio (R = 100: 1), is used in our specifications. A wire grid polarizer can also be characterized by the degree of polarization, defined as P = (T1 - T2)/(T1 + T2).

Extinction ratios greater than 40,000:1 can be achieved by the use of two wire grid polarizers in series with their grids parallel (the overall extinction ratio is the product of the extinction ratio of the individual polarizers).

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