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A polarimeter is an optical instrument used in the transmissive mode for determining the polarization state of a light beam,
or the polarization-altering properties of a sample, such as diattenuation, retardation and depolarizion.1 (Reflective
"polarimeters" are typically called ellipsometers.) Polarimeters can, thus, be broadly categorized as either light-measuring
polarimeters or sample-measuring polarimeters. A light-measuring polarimeter is also known as a Stokes polarimeter,
which measures the polarization state of a light beam as described by the Stokes parameters. A sample-measuring
polarimeter is also known as a Mueller polarimeter, which measures the complete set or a subset of polarization-altering
properties of a sample.
Polarimeters can also be categorized by whether they measure the complete set of polarization properties. If a Stokes
polarimeter measures all four Stokes parameters, it is called a complete Stokes polarimeter; otherwise, an incomplete or a
special Stokes polarimeter. Similarly, there are complete and incomplete Mueller polarimeters. Nearly all samplemeasuring
polarimeters are incomplete or special polarimeters, particularly for industrial applications. These special
polarimeters bear different names. For example, a circular dichroism spectrometer, which measures the differential
absorption between left and right circularly polarized light (▵;A= AL - AR), is a special polarimeter for measuring the
circular diattenuation of a sample; a linear birefringence measurement system is a special polarimeter for measuring the
linear retardation of a sample.
Polarimeters have a broad range of applications in both academic research and industrial metrology. Polarimeters are
applied to chemistry, biology, physics, astronomy, material science and many other scientific areas. Polarimeters are used
as metrology tools in the semiconductor, fiber telecommunication, flat panel display, pharmaceutical and many other
industries. Different branches of polarimetry have established their own scientific communities, within which regular
conferences are held.2-6 Tens of thousands of articles have been published on polarimeters and their applications, including
books and many review articles.1, 7-15 In this paper, I will focus on polarimeters using the photoelastic modulator (PEM).16-18
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