waveplates plate retarders. a wave plate or retarder is an optical device that alters the...
TRANSCRIPT
WAVEPLATES
PLATE RETARDERS
A wave plate or retarder is an optical device that alters the
polarization state of a light wave traveling through it.
Waveplate (Retarders)
•Full Wave Plate
•Half Wave Plate
•Quarter Wave Plate
0 et n n
Optical path length
Phase difference
00
2et n n
Quarter wave, Half wave and Full wave
4
2
2
2
Half-Wave Plate
Desired Result Method
Change linear polarization to circular polarization
.
Change circular
polarization to linear
Change the handedness of
circular polarization
Rotate linear polarization to
a more desirable orientation
Insert a λ/4 plate with axis at 45° to the input polarization
Insert a λ/4 plate with axis at
45° to the desired output
polarization.
Insert a λ/2 plate – orientation
unimportant.
Insert a λ/2 plate with axis at ½
the desired rotation.
Interference of polarized light
Fresnel-Arago laws
1. Two coherent rays polarised at right angles do not interfere
2. Two parallel coherent polarised rays will interfere in the same way as will ordinary light
Optical Activity
The two hands are "non-superimposable mirror images".
An optically active compound and its mirror image are called enantiomers or optical isomers
Optically active medium
Polarimetry
Sugar, Glucose and Fructose
Sugar (Sucrose or Cane sugar)
Glucose-D ( Dextrose or Grape sugar)
Fructose (Levulose or Fruit sugar)
Specific rotation
52.7
66.47
- 92
o
o
o
112212 OHC
6126 OHC
6126 OHC
Half Shade plate
A OO´
E´EQ´ Q
PolarizingSunglass
Antiglare screen
Problem
Unpolarized light of intensity I0 is incident normally on three
polaroid sheets P1, P2 and P3 all arranged in series. The pass
axis of each polaroid sheet makes an angle of 450 with the
earlier sheet.
(i) What is the intensity of the transmitted beam?
(ii) What is the intensity of the transmitted beam if the Polaroid
sheet P2 is replaced with a quarter wave plate Q2 with its
optic axis along the pass axis of P2?