1. Polarisation

2. Electromagnetic Waves
E Field
Electromagnetic waves consist of E (electric) fields and H (magnetic) fields
H Lines
H Field
Direction of Propagation
E Lines

3. They form an ORTHOGONAL Set
E Field
That is, in linear media, they are all at right angles to each other.
H Lines
H Field
Direction of Propagation
E Lines

4. We always use the E field as our reference
H Lines
H Field
Direction of Propagation
E Lines
Because E (electric) fields are easy to measure.

5. Waves and Vectors
The wave can be described by a ROTATING VECTOR.

6. Any general E field can be represented by two components, Ex and Ey.
They are always oriented in space at right angles to each other

7. But Ex and Ey need not stay in phase.

8. The resulting E field will have one of three polarisations
Linear
Circular
Elliptic
Both elliptic and circular polarisations are referred to as random polarisation.

9. Linear Polarisation
Both Ex and Ey are present with equal magnitude and they stay in phase The resultant E wave describes a straight line, fixed in space as it propagates.

10. Circular Polarisation
Both Ex and Ey are present with equal magnitude and 90 degrees phase difference. The resultant E wave describes a circle as it propagates.

11. Elliptical Polarisation
Both Ex and Ey are present
They may have:
equal magnitude and do not stay in phase or
unequal magnitude and do not stay in phase.
The resulting E wave describes an ellipse as it propagates.

12. Action of a Polariser.
Only one polarisation of the wave is allowed through. All others are stopped.

13. Polarising elements in a confocal microscope system.
Brewster windows
Phase plates
Beam splitters
Dichroics
Prisms
Diffraction gratings
Coated mirrors
Polaroid filters

14. Some Applications

15. Sun Glasses

16. Pockels Cell

17. Brewster windows
The refracted wave does not suffer any loss in the window.

18. Liquid crystal displays