Polarized Light Polarized Light
Transmission Axis
Inside Polarizers
Linear Glass Polarizers ............................173, 178
Wire Grid Polarizers ..........................174-175, 177
Infrared Polarizers ............................................175
Linear Plastic Polarizers ..................................176
Linear Film Polarizers ...............................176-177
Crystalline Polarizers ...............................179, 184
Circular Polarizers ............................................180
Waveplates/Retarders..............................181-184
Optical Isolators ..............................................184
A common application for polarizers and retarders is optical
isolation. Isolation, similar to extinction, is the percentage of
light blocked by the return pass through the polarizers.
Polarization States
Customized
Polymer Polarizers
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TECHNICAL NOTE
Understanding and controlling the polarization state of light is important in many optical system applications.
Polarization eff ects are used to analyze chemical reactions, measure changes in magnetic fi elds,
evaluate stresses in an object, modulate and attenuate laser light, and investigate molecular structures. In
imaging systems, polarizers are often used to reduce glare and improve contrast.
CLASSIFICATION OF POLARIZATION
Light is an electromagnetic wave and the electric fi eld of this wave oscillates perpendicularly to the direction
of propagation. Polarized light is light with a well defi ned direction of the electric fi eld,1
Linear or Plane Polarization - The electric fi eld of linear or plane polarized light is confi ned to a single
plane along the direction of propagation of the light wave.
Circular Polarization - The electric fi eld of circularly polarized light consists of two equal amplitude,
orthogonal linear components that have a relative phase diff erence of π/2. The resultant electric fi eld
traces a circle as the wave propagates.
Random (Unpolarized) - Light that exhibits no long-term preference as to vibration pattern1. Mathematically,
this can be described by two orthogonal linear components that have a relative phase diff erence
that varies rapidly and randomly2.
LINEAR POLARIZERS
Linear polarizers are optical elements that are designed to transmit a specifi c polarization or separate a
given polarization into two orthogonal linear components.
Extinction Ratio and Degree of Polarization: The polarizing properties of a linear polarizer are
typically defi ned by the degree of polarization or polarization effi ciency, P, and its extinction ratio, ρρ.
Following the formalism given in the Handbook of Optics3, the principal transmittances of the polarizer
are T1 and T2. T1 is the maximum transmission of the polarizer and occurs when the axis of the polarizer
is parallel to the plane of polarization of the incident polarized beam. T2 is the minimum transmission of
the polarizer and occurs when the axis of the polarizer is perpendicular to the plane of polarization of
the incident polarized beam.
Transmission Axis
Parallel to the
Polarized Input Light
TLinear Polarizer 1
Perpendicular to the
Polarized Input Light
TLinear Polarizer 2
In optics it is standard to describe linear
polarization in reference to the surface or
interface that the light is incident upon. The
plane of incidence is normal to the surface
or interface.
S-Polarization State: Polarization that is
perpendicular to the plane of incidence.
The S notation in “S-Polarization” comes
from the German word for perpendicular
(senkrecht). It may be helpful to think of
S-Polarization as “skipping” parallel to the
surface of incidence.
P-Polarization State: Polarization that
is parallel to the plane of incidence. The P
notation in “P-Polarization” comes from the
German word for parallel (parallel). A common
mnemonic for remembering P-Polarization
is to think of P-Polarized light as “plunging”
into the surface.
P = (T1 - T2) / (T1 + T2) and, ρp = T2 / T1
The extinction performance of a linear polarizer is often expressed as 1 / ρp : 1
This parameter ranges from less than 100:1 for economical sheet polarizers to 106:1 for high quality birefringent
crystalline polarizers. The extinction ratio typically varies with wavelength and incident angle and
must be evaluated along with other factors like cost, size, and polarized transmission for a given application.
POLARIZER TYPES
Linear Polarizers are often classifi ed into four broad categories: refl ective, dichroic, birefringent (crystalline),
and thin fi lm.
Refl ective Polarizers refl ect one polarization state and transmit the orthogonal state. Many diff erent
types of refl ective linear polarizers are available including polarizing plate beamsplitters, Brewster windows,
polarizing cube beamsplitters, and wire grid polarizers. Refl ective polarizers are suitable for a
wide variety of applications ranging from laser cavities to heads up displays. When choosing a refl ective
polarizer for a specifi c application, consider extinction performance, a need to access both orthogonal
polarization states, wavelength, and angle sensitivity before making your purchase.
Dichroic Polarizers are absorptive polarizers that transmit the desired polarization and absorb unwanted
polarization. This is achieved via anisotropy in the absorption in the polarizer material. Most
dichroic polarizers have good extinction performance relative to cost. Dichroic polarizers are well suited
for microscopy, imaging, and display applications, and are often the only choice when large apertures
are required.
Birefringent Polarizers typically separate the propagation direction of the two polarization states of
the incident light using a birefringent crystalline material. The relative orientation of the optical axes
of the crystals in the polarizer determines the direction of propagation of the polarization states in the
polarizer. Birefringent polarizers typically have high extinction ratios and high optical damage thresholds,
but have relatively high cost as they use large naturally occurring crystals. Birefringent polarizers are
available in a variety of geometries, which can be used for high power laser applications.
Thin Film Polarizers feature thin fi lm dielectric coatings that separate the s- and p- polarizations of
light through interference eff ects. Typically, these polarizers refl ect the s-polarization and transmit the
p-polarization of incident light. The deposited dielectric coatings are designed to have high damage
thresholds and high extinction ratios, making these polarizers ideal for use in laser applications.
1. Shurcli , W.A., and Ballard, S. S. (1964) Polarized Light, (p. 9). D. Van Nostrand Company, Inc., Princeton, NJ.
2. Hecht, E., and Zajac, A. (1979) Optics (p. 223).Addison-Wesley Publishing Company, Reading, MA.
3. Bennett, J. M. (1995). Polarization. In M. Bass (Ed.), Handbook of Optics, Vol. I (pp,5,1 – 5,16). Optical Society of America. McGraw-Hill, Inc, New York, NY.
• Wide Range of Polymer Polarizers for
Visible Applications
• Custom Sizes and Shapes for Linear
and Circular Polarizers, and Retarders
• Lamination on Glass or Plastic Substrates
for Improved Stability
• Single Piece Minimum Order Quantities
with Short Lead Times
For more information on
customized polarizers, visit
www.edmundoptics.eu/
capabilities/polarizers
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