Polarisation

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

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

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.

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

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

But Ex and Ey need not stay in phase.

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

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.

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.

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.

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

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

Some Applications

Sun Glasses

Pockels Cell

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

Liquid crystal displays