Good Example Of Wave Plate Essay

A wave plate or retarder is simply a device that converts light from one polarized form to another by introducing a phase shift between the two orthogonal polarized components of light. Polarization forms a fundamental part of optics and optical instruments i.e. optical compensators, retarders and sensors among others. This is only possible when light is viewed as an electromagnetic wave with electric and magnetic components. The speeds of these two components are varied as they enter a crystal surface according to the crystal’s refractive index. Therefore, the relative direction of light in motion to the electric component (also known as polarization) can be measured owing to the differences in speed of propagation (Hecht, E., 1987).

Principle of Operation of a wave plate

A wave plate functions by combining or separating different linearly polarized light wavelengths. The principle of operation also known as the retardation theory explains the effect of the optical material through which light passes. Some optical materials have similar properties i.e. elasticity, refractive index while others i.e. crystals have varied properties. This leads to a phenomenon known as birefringence where different light wavelengths polarized in different directions passing through an optical material of varied refractive indexes experience different phase shifts (Redoptronics.Com, (2010). Different refractive indexes mean that the different light components will be propagated with different speeds through the crystal. Therefore light components propagated parallel to the optical axis (the path of light with a constant refractive index also considered as the main axis of the birefringent material) experience ordinary index while those propagated perpendicular to the optical axis are polarized by the extraordinary index (Born, M &Wolf, E., 1980). This event leads to the formation of a normal axis and fast axis of a crystal.
There are two types of wave plates namely the half wave and quarter wave plates. The quarter wave plate converts linearly into circular polarized light. It produces two orthogonal polarized light components to the main axis but in opposite directions. The half wave plate rotates a linearly polarized light through an angle.

References

Hecht, E. (1987). Optics, 2nd ed. Reading, MA: Addison-Wesley Publishing Co.
Born, M.; Wolf, E. (1980). Principles of Optics. Oxford: Pergammon Press.
Redoptronics.Com (2010). Wave plate. Retrieved from www.redoptronics.com/waveplate.html