Waveplates (retardation plates or phase shifters) are made from materials which exhibit birefringence. The velocities of the extraordinary and ordinary rays through the birefringent material varies inversely with their refractive indices. This difference in velocities gives rise to a phase difference when the two beams recombine. In the case of an incident linearly polarized beam this is given by ¦Á=2¦Ðd(ne-no)/¦Ë, where ¦Á is phase difference; d is thickness of waveplate; ne, no are refrective indices of extraordinary and ordinary rays respectively; ¦Ë is wavelength. At any specific wavelength the phase difference is governed by the thickness of the retarder.
¦Ë/ 2 Waveplates
The thickness of a half waveplate is such that the phase difference is 1/2-wavelength (¦Ë/2, true zero order) or certain multiple of 1/2-wavelength ((2n+1)¦Ë/2, multiple order).
A linearly polarized beam incident on a half waveplate emerges as a linearly polarized beam but rotated such that its angle to the optical axis is twice that of the incident beam. Therefore, half-waveplates can be used as continuously adjustable polarization rotators. Half-waveplates are used to rotate the plane of polarization, electro-optic modulation and as a variable ratio beamsplitter when used in conjunction with a polarization cube.
¦Ë/ 4 Waveplates
The thickness of the quarter waveplate is such that the phase difference is 1/4-wavelength (¦Ë/4, true zero order) or certain multiple of 1/4-wavelength ((2n+1)¦Ë/4, multiple order).
If the angle ¦È (between the electric field vector of the incident linearly polarized beam and the retarder principal plane) of the quarter waveplate is 45 degree , the emergent beam is ircularly polarized. When a quarter waveplate is double passed, i.e. by mirror reflection, it acts as a half waveplate and rotates the plane of polarization to certain angle. Quarter waveplate are used in creating circular, ellipsometry, optical pumping, suppressing unwanted reflcetion and optical isolation.
Standard Waveplates
ORTER's waveplates, including full-wave (¦Ë), half-wave (¦Ë/2), quarter-wave (¦Ë/4) and octadic-wave (¦Ë/ 8) plates are widely used in synthesis and analysis of light in various states of polarization. The standard wavelengths of ORTER's waveplates are listed below for your reference.
Our product line includes:
Low-Order Waveplates
Polarizing Rotaters
True Zero-Order Waveplates