Phase-shifting mirrors convert linearly polarized light into circularly polarized light. This effect is particularly useful in laser material processing, where linear polarization would lead to axis-dependent, non-uniform results, e.g. in cuts or drill holes.
Contrary to the way a waveplate works, i.e. transmission of a laser beam under perpendicular incidence, a phase-shifting mirror works by means of reflection and an angle of incidence of 45°. The layer system is optimized to achieve a specific phase difference between s- and p-polarized light.
A typical application is a phase difference of λ/4 ≙ 90° = ℼ/2 at an angle of incidence of 45° to generate circularly polarized radiation for an incident beam with linear polarization. We also realize other values upon customer request.