WIRE GRID POLARIZERS Optometrics Manufactures Wire Grid Polarizers Using Two Methods:
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.
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.
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, 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.
Wire grid polarizers transmit 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. Wire grid polarizers 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).
RULED WIRE GRID POLARIZERS Optometrics manufactures wire grid polarizers by ruling precisely spaced grooves directly into a highly polished CaF2 or ZnSe substrate. The ruling process forms sharp, well defined peaks which are then coated with aluminum by vacuum deposition at an oblique angle. The direct ruling and coating process results in a series of closely spaced, highly conductive wires with a high extinction ratio and an inherently high damage threshold. No intermediate absorbing materials are required between the substrate and aluminum coating, minimizing localized heating and allowing the use of the polarizers with relatively high power lasers.
Wire grid polarizers can be used at angles of incidence up to 45 degrees with collimated, diverging or converging beams without loss of efficiency and little lateral displacement of the transmitted beam. The optical path of a wire grid polarizer is simply the thickness of the substrate.
STANDARD SIZES AND OPTIONS Ruled wire grid polarizers are available in five standard sizes (15 mm square,15, 25, 38 and 50 mm diameter). Ruled polarizers are available unmounted, mounted in a double protective ring or mounted in a bench mountable stage which allows 360° rotation.
If your application requires a different size or shape, please contact us for price and delivery. OEM inquires are welcome.
CAUTION: The surface of a wire grid polarizer, like any diffraction grating, is extremely delicate. Nothing should ever be allowed to touch the surface of the polarizer. Handling, when necessary, should be by the edge only and with protected fingers. Careful removal of dust by gentle air flow is the only cleaning procedure recommended by Optometrics.
Ruled Wire Grid Polarizers (Add $195 per side for AR Coating on ZnSe)
