Collimation testing with optically active materials.

A novel method to test the collimation of laser beams with optically active mediums and a pair of crossed polarizers is presented. Optically active materials rotate the plane of polarization of incident plane-polarized light. A decollimated laser beam passing through such a material will experience a greater effective thickness than a collimated laser beam, resulting in greater outputs. In this method the output intensity variation is related to the amount of decollimation of the incident beam, and the method does not require any referencing or fringe analysis and is easy to implement.