Circular Polarisation

Circular Polarisation

  • Electric field of the circular polarized light rotates but magnitude remains constant.
  • Produced from the superposition of two waves that have the same amplitude and wavelength and are polarized in two perpendicular planes with a phase difference of 90 degrees between them.
Animation of Left-handed/Counter-Clockwise circularly polarized Light.

Circular polarization by quarter waveplate

Creating circular polarized light

  • A quarter waveplate is made of a type of birefringent material and it’s thickness is some multiple of one quarter wavelength of a light of a particular frequency.
  • Incident light polarized at 45 degrees to the optic axis enters the quater waveplate and is divided into two rays having equal magnitude. The quarter waveplate retards the ray of light associated with the larger index of refraction by 90 degrees in phase (a quarter wavelength) with respect to that associated with the smaller index.
  • With equal magnitudes of two rays of light with 90 degrees phase difference and planes of polarization at right angles to each other, circularly polarized light with amplitude square root 2 of the amplitude of either rays of light is produced.


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