SEMI MF1763 - Test Method for Measuring Contrast of a Linear Polarizer -

Abstract

Polarizer contrast is important in polarimetry systems, ellipsometers, optical modulators, shutters, and target signature discrimination based on polarized radiation.

This Test Method covers measurement of polarizer contrast. It provides procedures suitable for use in service evaluation, manufacturing control, or for research and development purposes. They are not recommended for use in acceptance testing until their precision has been evaluated by interlaboratory comparison unless the parties to the test conduct suitable correlation studies.

The procedures in this Test Method are applicable to polarizers that operate in a transmissive mode at near-normal incidence. Angular or translative offset of the transmitted beam is acceptable if the entire transmitted beam power can be measured.

A distinction is made between contrast, which is an intrinsic polarizer property, and extinction, which is a comparison between two polarizers. Use of contrast to characterize polarizers is encouraged because it is an intrinsic property of the polarizer. Use of extinction to characterize polarizers is discouraged because it is an average between two polarizers and not specific to either one.
 

The polarizer size or aperture is not limited in this Test Method, but the operator must appreciate that the contrast is an average over the beam spot on the polarizer. Contrast measured at one location on the aperture does not necessarily apply to the entire aperture.

Three procedures are described. The first procedure is a direct contrast measurement that requires a linearly polarized light source with high contrast, CL. The second procedure is a comparison with a linearly polarized light source with known CL. The third procedure is an indirect contrast measurement that can use an unpolarized or polarized light source of unknown CL.
 

Direct Contrast Measurement — This is the preferred method for measuring C of a single polarizer. This method can be used if CL >> C for the polarizer to be tested. It is a simple, expedient, and accurate test method if a highly linear polarized light beam is available at the required wavelength. The source is normally a polarized laser beam in combination with a high-contrast prism polarizer. A tunable broadband source can also be used if a high-contrast polarizer is available for the wavelength of interest.
 

Contrast Measurement with Comparison — This method is used if CL is approximately equal to C for the polarizer to be tested. The value of CL must be known to obtain the correct C for the polarizer.
 

Indirect Contrast Measurement — This method requires three polarizers that have similar C. This test method can be used with any light beam regardless of the contrast of the light beam. It is the only method that can be used when the available CL << C for the polarizer to be tested.

Referenced SEMI Standards (purchase separately)
None.

Revision History
SEMI MF1763-0318 (Reapproved 1023)
SEMI MF1763-0318 (technical revision)
SEMI MF1763-0706 (Reapproved 1111)
SEMI MF1763-0706 (technical revision)
SEMI MF1763-96 (Reapproved 2002) (first SEMI publication)

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