Metal cutting has long been known to be sensitive to the polarisation of the laser beam used.

Circular polarisation is used to ensure even cutting or welding in different axes. Unfortunately most high power lasers have a linearly polarised output.

To convert linear polarisation to circular polarisation a ¼ wave phase retarding mirror is needed. Often these are known as polarisers, ECQ mirrors, or 90 degree retarders.

Our supplier stocks a range of standard ¼ wave phase retarding mirrors both from copper and silicon, as well as offering custom designs.

Accurate control of the phase retarding value of the coating is needed to ensure high quality circular polarisation for consistent cutting. Typical values of the phase shift are 90 degrees +/- 2 degrees.

It is essential that mirrors before and after the polarising mirror do not affect the polarisation of the beam (i.e they have zero phase shift). Gold coated mirrors are recommended for this purpose having one of the lowest phase shifts known (< +/-1 degree).