Light Polarization and Stokes Parameters
The polarization state of an electromagnetic wave can conveniently be described by a set of Stokes parameters. On the left, the polarization ellipse describes the motion of the optical electric field (,) in a plane transverse to the light propagation direction. On the right are the corresponding Stokes parameters defined in terms of intensity difference measurements
E
H
E
V
iΔϕ
e
S
x
I
H
I
V
2
E
H
2
E
V
S
y
I
-45°
I
+45°
E
H
E
V
S
z
I
L
I
R
E
H
E
V
where the intensities of the polarization components (: horizontal, : vertical, ±45: along diagonals, : circular left, : circular right) are normalized to the total light intensity. The parameters that you can vary are the orientation of the ellipse, its degree of linear polarization , where and are the intensities measured along the major and minor axes, and its handedness (direction of rotation). For 100% polarized light, the endpoint of the Stokes vector =(,,) lies on a unit sphere called the Poincaré sphere.
H
V
°
L
R
DOLP=-+
I
max
I
min
I
max
I
min
I
max
I
min
S
S
x
S
y
S
z
THINGS TO TRY
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