How to change the polarization of the light

[chenhon5]

Is anybody knows what kind of equipment or lens can be used to change the direction of the polarization of the laser light (electrical field and magnetic field, but not the direction of the light)? Thanks.

 

[Cthugha]

You can use a half wave plate to rotate the polarization of linearly polarized light. Also you can use quarter wave plates to convert linearly polarized light to circularly polarized light and vice versa. Both usually consist of some birefringent material.

 

[mikelepore]

Some materials are called "optically active" or "birefringent", and they rotate the plane of polarization of light passign through them, because the molecules have some spiral pattern or the molecules have been subjected to some stress. I saw an instructor do demonstrations passing polarized light through several plastic items: a plastic protractor, cellophane, and Scotch tape. He also said that mica is an optically active mineral.