Polarization Basics
• The equations
represent a pair of plane waves: the two components of the electrical field of an EM wave propagating in the z direction, not necessarily monochromatic.
• The amplitudes Eox,y(t) and phasesδx,y(t) fluctuate slowly with respect to the rapid oscillation of the carrier cos(ωt).
⎩⎨
⎧
+
=
+
=
)]
( cos[
) ( ) (
)]
( cos[
) ( ) (
t t t E t E
t t t E t E
y oy
y
x ox
x
δ ω
δ ω
z Ex
Ey E
Polarization Basics
If we eliminate the term cos(ωt) between the two equations, and defineδ(t)= δy(t)-δx(t), we find the polarization ellipse (valid in general at a given time), which is the locus of points described by the optical field as it propagates:
⎩⎨
⎧
+
=
+
=
)]
( cos[
) ( ) (
)]
( cos[
) ( ) (
t t t E t E
t t t E t E
y oy
y
x ox
x
δ ω
δ ω
) ( sin ) ( )cos ( ) (
) ( ) ( 2 ) (
) ( ) (
)
( 2
2 2
2 2
t t t
E t E
t E t E t E
t E t E
t E
oy oy
y x oy
y ox
x + −
δ
=δ
fast fast fast
slow slow slow
slow slow
t ) ( ) ( ) (t E t E t
E x y
r r
r = +
z Ex
Ey E
Polarization Basics
• For purely monochromatic waves, amplitudes and phases must be constant with time:
And the polarization ellipse is also constant:
⎩⎨
⎧
+
=
+
=
] cos[
) (
] cos[
) (
y oy
y
x ox
x
t E t E
t E t E
δ ω
δ ω
δ
δ
22 2
2 2
sin )cos ( ) ( 2 ) ) (
( + − =
oy ox
y x oy y ox x
E E
t E t E E
t E E
t E
fast fast fast
t ) ( ) ( ) (t E t E t
E x y
r r
r = +
z Ex
Ey E
Polarization Basics
• In general a beam of light is “elliptically polarized”.
• The polarization ellipse degenerates to special forms for special values of the amplitudes and of the phases.
• Linear polarized waves: when the ellipse collapses to a line, i.e. whenδ=0,π. The direction of the E vector remains constant.
• Circularily polarized waves: when the ellipse reduces to a circle, i.e. when δ=π/2, 3π/2 and Eox=Eoy=Eo.
E x y
E x y
E x y
Polarization Basics
• The polarization ellipse is specified by the amplitude parameters Eox,Eoy,δ.
• But it can be expressed equivalently by the elliptical parameters:
• Orientation angleψ:
• Ellipticity angle χ :
• For linearly polarized light χ=0.
ψ b a
x y’
x’
y
2 2
cos 2 2
tan
oy ox
oy ox
E E
E E
= − δ
ψ
a
±b χ= tan
2 2
sin 2 2
sin
oy ox
oy ox
E E
E E
= + δ
χ
Stokes Parameters
• Our detectors are too slow to follow the time evolution of the EM field. What we can measure are time averages, over periods much longer than 2π/ω.
• Due to the periodicity of the EM waves, it is enough to compute time averages over a single period of oscillation. These are represented by the symbol <…>.
• So we take the time average of the polarization ellipse:
δ
δ
22 2
2 2
sin ) cos ( ) ( 2 ) ( )
( + − =
oy ox
y x oy y ox x
E E
t E t E E
t E E
t E
Stokes Parameters
• Multiplying by 4Eox2Eoy2we find
• Since Ex(t) and Ey(t) are sine waves, we can compute their time averages and substitute above:
• Since we want to express this in terms of intensities, we can add and subtract Eox4+Eoy4:
2 2
2 2
2
) sin 2 ( cos ) ( ) ( 2 8
) ( 4 ) ( 4
δ
δ
ox oyy x oy ox
y ox x
oy
E E t
E t E E E
t E E t E E
=
−
+ +
2 2
2 2 2 2
) sin 2 ( ) cos 2
( 2 2
δ
δ
ox oyoy ox
oy ox ox oy
E E E
E
E E E E
=
−
+ +
Stokes Parameters
• We find
• We define the Stokes Parameters:
• so that our equation reduces to
2 2
2 2 2 2 2 2
) sin 2 ( ) cos 2 (
) ( ) (
δ
δ
ox oyoy ox
oy ox ox oy
E E E
E
E E E E
=
−
+
−
− +
δ δ sin 2
cos 2
3 2
2 2 1
2 2
oy ox
oy ox
oy ox
ox oy o
E E S
E E S
E E S
E E S
=
=
−
= +
=
2 3 2 2 2 1
2 S S S
So
= + +
Stokes Parameters
• If light is not purely monochromatic, the amplitudes and phases fluctuate with time.
• It can be shown that, in general,
• The = sign is valid for fully polarized light, while the > sign is valid for partially polarized or unpolarized light. P=degree of polarization:
• The intensity is related to So:
• The orientation of the polarization ellipse is related to S1and S2:
• The ellipticity of the polarization ellipse is related to S3:
2 3 2 2 2 1
2 S S S
So≥ + +
1 2 2 2
cos 2 2
tan S
S E E
E E
oy ox
oy
ox =
= − δ
ψ
o oy ox
oy ox
S S E E
E
E 3
2 2
sin 2 2
sin =
= + δ
χ
δ δ sin 2
cos 2
3 2
2 2 1
2 2
oy ox
oy ox
oy ox
ox oy o
E E S
E E S
E E S
E E S
=
=
−
= +
=
2 2
ox oy
o E E
S = +
1 0
2 3 2 2 2 1
≤
≤
+
= +
=
P S
S S S I P I
o total
pol
Stokes Parameters
• Note that, for linear polarized light (δ=0), both parameters S1 and S2represent the difference in intensity carried by two orthogonal components:
• S1is the difference in intensity between the components along axis x and y
• S2is the difference in intensity between the components along two axisx’and y’rotated 45o with respect to x and y.
x y
x y
y’
x’
2 2
1 Ex Ey
S = −
2 ' 2
' ' ' ' '
2 2
1 2 1 2 1 2
2 1
2ExEy Ex Ey Ex Ey Ex Ey
S = −
⎥⎦⎤
⎢⎣⎡ +
⎥⎦⎤
⎢⎣⎡ −
=
=
Ex
Ey
Ex’
Ey’ 45o
Stokes Parameters: examples
• Unpolarized light:
δ=random
<Eox2>=<Eoy2>=Io
• Linearly polarized light:
– Horizontal(Eoy=0) Vertical (Eox=0) +45o (Eoy= Eoy; δ= 0) θo
• Circular polarized light:
– Left Right
δ δ sin 2
cos 2
3 2
2 2 1
2 2
oy ox
oy ox
oy ox
ox oy o
E E S
E E S
E E S
E E S
=
=
−
= +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= 0 0 0 1 2Io Sr
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= 0 0 1 1
Io
Sr
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= − 0 0 1 1
Io
Sr
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= 0 1 0 1
Io
Sr
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= 0
2 sin
2 cos
1
θ θ Io
Sr
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
−
= 1 0 0 1
Io
Sr
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= 1 0 0 1
Io
Sr
Stokes Parameters
• The waves can be represented as complex functions:
• This helps in the time-averaging process needed to compute the Stokes Parameters. They can be rewritten as follows (Stokes vector):
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
− +
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
δ δ sin 2
cos 2 ) (
2 2
2 2
*
*
*
*
*
*
*
*
3 2 1
oy ox
oy ox
oy ox
oy ox
x y y x
x y y x
y y x x
y y x x o
E E
E E
E E
E E
E E E E i
E E E E
E E E E
E E E E
S S S S
⎩⎨
⎧
+
= +
=
+
= +
=
)]
( exp[
] cos[
) (
)]
( exp[
] cos[
) (
y oy
y oy
y
x ox
x ox
x
t i E t E t E
t i E t E t E
δ ω δ
ω
δ ω δ
ω
Stokes Parameters
• The Stokes vector can also be expressed in terms of So, ψ, χ.
• From
• And from
• Using
we find S1, so we have:
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
χ ψ χ
ψ χ
2 sin
2 sin 2 cos
2 cos 2 cos
1
3 2 1
o o
S S S S S
δ ψ
ψ 2 cos we can write tan2 2
tan 2 2 S2 S1
E E
E E
oy ox
oy
ox =
= −
δ χ
χ 2 sin we can write sin2 2
sin 2 2 3 o
oy ox
oy
ox S S
E E
E
E =
= +
2 3 2 2 2 1
2 S S S
So = + +
Poincare’
Classical measurement of the Stokes Parameters
• The measurement of the 4 Stokes Parameters needs two optical components:
– A retarder (wave plate): it is a phase-shifting element, whose effect is to advance the phase of the x component byφ/2and to retard the phase of the y component by -φ/2. So the field emerging from the retarder is E’x= Exei φ/2and E’y= Eye-i φ/2 – A polarizer. The optical field can pass only along one axis, the
transmission axis. So the total field emerging from the polarizer is E”=E’xcosθ+E’ysinθ, where E’ is the incident field and θ is the angle of the transmission axis.
• So the beam arriving on the detector is E”=Ex ei φ/2cosθ+Eye-i φ/2sinθ
φ θ
source retarder polarizer
detector
Classical measurement of the Stokes Parameters
• E”=Ex ei φ/2cosθ+Eye-i φ/2sinθ
• The detector measures its intensity, i.e. I= E”E”*
• So we get
• Which can be rewritten using the half-angle formulas:
φ θ
source retarder polarizer
detector
θ θ θ
θ
θ θ
φ ϑ
φ
φsin cos sin cos
sin cos
) , (
*
*
2
* 2
*
i y x i
y x
y y x x
e E E e
E E
E E E E I
+ +
+ +
=
−
( ) ( )
( ) ( )
⎥⎥⎦
⎤
⎢⎢
⎣
⎡
− + +
+
− +
= +
θ φ θ
φ φ θ
ϑ cos sin2 sin sin2
2 cos )
,
( * * * *
*
*
*
* 2 1
x y y x x
y y x
y y x x y y x x
E E E E i E
E E E
E E E E E E E E I
2 2 sin 2
2 cos 1 2 2
2 cos 1
2 sin sin cos
cosθ=+ θ θ=− θ θ θ= θ
[
θ φ θ φ θ]
φ
ϑ, ) cos2 cos sin2 sin sin2
( 21S S1 S2 S3
I = o+ + +
Classical measurement of the Stokes Parameters
• This is the formula derived in 1852 by Sir George Gabriel Stokes.
• The first three parameters can be measured by removing the retarder (φ=0) and measuring the intensity with three orientations of the polarizerθ=0o,45o,90o:
• The fourth parameter can be measured by inserting a 90oretarder (quarter wave plate):
φ θ
source retarder polarizer
detector
[
θ φ θ φ θ]
φ
ϑ, ) cos2 cos sin2 sin sin2
( 2 1 2 3
1S S S S
I = o+ + +
[ ]
[ ]
[ ]
[ ]
⎪⎪
⎩
⎪⎪
⎨
⎧
+
=
−
= +
= +
=
2 3 1 2 1 1 2 2 1 2 1 1
) 90 , 45 (
) 0 , 90 (
) 0 , 45 (
) 0 , 0 (
S S I
S S I
S S I
S S I
o o o
o o o
o o o
o o o
⎪⎪
⎩
⎪⎪
⎨
⎧
−
−
=
−
−
=
−
= +
=
) 0 , 90 ( ) 0 , 0 ( ) 90 , 45 ( 2
) 0 , 90 ( ) 0 , 0 ( ) 0 , 45 ( 2
) 0 , 90 ( ) 0 , 0 (
) 0 , 90 ( ) 0 , 0 (
3 2
1
o o o o o o
o o o o o o
o o o o
o o o o o
I I I
S
I I I S
I I S
I I S
Classical measurement of the Stokes Parameters
• The great advantage of the Stokes Parameters is that they are observable. The polarization ellipse is not (too fast).
• Moreover, the Stokes parameters can be used to describe unpolarized light: light which is not affected by the rotation of a polarizer or by the presence of a retarder. Stokes was the first one to describe mathematically unpolarized and partially polarized light.
• It is evident from Stokes formula that, for unpolarized light, S1=S2=S3=0, while So>0.
• The fully polarized light had
• The intermediate state is partially polarized light, where
φ θ
source retarder polarizer
detector
[
θ φ θ φ θ]
φ
ϑ, ) cos2 cos sin2 sin sin2
( 2 1 2 3
1S S S S
I = o+ + +
2 3 2 2 2 1
2 S S S
So= + +
2 3 2 2 2 1
2 S S S
So≥ + +
Partially polarized light
• The Stokes parameters of a combination of independent waves are the sums of the respective Stokes parameters of the separate waves.
• If we combine a fully polarized wave with an
independent, unpolarized one, we find partially polarized light.
• This expression will be useful in the following.
1 0
2 3 2 2 2
1+ + ≤ ≤
=
= P
S S S S I P I
o total
pol
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛ +
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
−
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
=
3 2 1
3 2 1
0 0 ) 0 1 (
S S S S P S P S S S S S
o o o
Polarization-active optical components
• When a beam of light interacts with matter its polarization state is almost always changed.
• It can be changed by
– changing the amplitudes – changing the phases – changing the directionsof the orthogonal field components.
• Their effect can be described by means of the Mueller matrices: M is a 4x4 matrix such that the emerging Stokes vector is S’=M S .
Polarizer (Diattenuator) Rotator
Wave-plate (Retarder)
1) Polarizer or Diattenuator
• It attenuates the orthogonal components of an optical beam unequally:
• Using the definitions of S and S’
• And inserting the expressions for E’
we get
⎪⎩
⎪⎨
⎧
=
=
y y y
x x x
E p E
E p E
' '
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
− +
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
) ( ' '* ' '*
'*
' '*
' '*
' '*
' '*
' '*
'
' 3 ' 2 ' 1 '
x y y x
x y y x
y y x x
y y x x o
E E E E i
E E E E
E E E E
E E E E
S S S S
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
− +
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
)
( * *
*
*
*
*
*
*
3 2 1
x y y x
x y y x
y y x x
y y x x o
E E E E i
E E E E
E E E E
E E E E
S S S S
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
+
−
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1 2
2 2 2
2 2 2 2
' 3 ' 2 ' 1 '
2 0 0 0
0 2 0 0
0 0
0 0
2 1
S S S S
p p p p p p p p
p p p p
S S S
S o
y x y x y x y x
y x y x o
Special cases
• If the diattenuator is simply an attenuator, i.e. if px=py=p we have a neutral density filter:
• If the Polarizer is ideal and horizontal, i.e. if py=0 we have
• If the Polarizer is ideal and vertical, i.e.
if px=0 we have
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1 2
' 3 ' 2 ' 1 '
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
S S S S
p
S S S
So o
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1 2
' 3 ' 2 ' 1 '
0 0 0 0
0 0 0 0
0 0 1 1
0 0 1 1
2
S S S S p
S S S
S o
x o
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛ +
−
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1 2
2 2 2
2 2 2 2
' 3 ' 2 ' 1 '
2 0 0 0
0 2 0 0
0 0
0 0
2 1
S S S S
p p p p p p p p
p p p p
S S S
S o
y x y x y x y x
y x y o x
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
−
−
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1 2
' 3 ' 2 ' 1 '
0 0 0 0
0 0 0 0
0 0 1 1
0 0 1 1
2
S S S S p
S S S
S o
y o
Polarizer:
• The characteristics of the polarizer pxand py can be rewritten in terms of new parameters p and α:
• With these parameters the Mueller matrix of a polarizer is:
• An ideal polarizer converts any incoming beam into a linearly polarized beam:
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛ +
−
− +
=
y x y x y x y x
y x y x
P
p p p p p p p p
p p p p M
2 0 0 0
0 2 0 0
0 0
0 0
2
1 2 2 2 2
2 2 2 2
sin cos
⎪⎩
⎪⎨
⎧
=
= α α p p
p p
ydef xdef
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
=
α α α
α
2 sin 0 0 0
0 2 sin 0 0
0 0 1 2 cos
0 0 2 cos 1
2 p2
MP
( )
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
± ±
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
±
±
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
0 0 1 1
2 1
0 0 0 0
0 0 0 0
0 0 1 1
0 0 1 1
2 1
1
3 2 1
' 3 ' 2 ' 1 '
S S S S S S
S S S S
o o o
2) Retarder
• It introduces a phase shift between the orthogonal components of an optical beam :
• Using the definitions of S and S’
• And inserting the expressions for E’
we get
⎪⎩
⎪⎨
⎧
=
=
− +
) ( ) (
) ( ) (
2 / '
2 / '
t E e t E
t E e t E
y i y
x i x
ϕ ϕ
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
− +
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
) ( ' '* ' '*
'*
' '*
' '*
' '*
' '*
' '*
'
' 3 ' 2 ' 1 '
x y y x
x y y x
y y x x
y y x x o
E E E E i
E E E E
E E E E
E E E E
S S S S
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
− +
− +
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
)
( * *
*
*
*
*
*
*
3 2 1
x y y x
x y y x
y y x x
y y x o x
E E E E i
E E E E
E E E E
E E E E
S S S S
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
=
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1
' 3 ' 2 ' 1 '
cos sin 0 0
sin cos 0 0
0 0 1 0
0 0 0 1
S S S S
S S S
So o
ϕ ϕ
ϕ ϕ
Special cases
• If the retarder is a quarter- wave plate (φ=90o):
• Such a retarder converts a +45olinearly polarized beam into a right/left circularly polarized beam:
• If the retarder is a half-wave plate (φ=180o):
• This reverses the ellipticity and orientation of the incomin polarization state.
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= −
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1
' 3 ' 2 ' 1 '
cos sin 0 0
sin cos 0 0
0 0 1 0
0 0 0 1
S S S S
S S S
So o
ϕ ϕ
ϕ ϕ
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= −
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1
' 3 ' 2 ' 1 '
0 1 0 0
1 0 0 0
0 0 1 0
0 0 0 1
S S S S
S S S
So o
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟±
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
= −
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
± 0
1 0 1
0 1 0 0
1 0 0 0
0 0 1 0
0 0 0 1
1 0 0 1
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
−
= −
⎟⎟
⎟⎟
⎟
⎠
⎞
⎜⎜
⎜⎜
⎜
⎝
⎛
3 2 1
' 3 ' 2 ' 1 '
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
S S S S
S S S
So o