90° Phase Shift
Most CO2 lasers produce a laser beam which has linear polarization. For cutting metal sheets, however, a beam with circular polarization is required if the cutting properties are independent of the cutting direction. To convert a beam from linear to circular polarization, a 90° phase retarder mirror (also called a Lambda/4-mirror) can be used. This mirror has a special coating which produces a phase shift of 90° between the s-and p-polarized components of the reflected beam. If these components have the same intensity and phase (corresponding to linear polarization), the reflected beam undergoes a phase shift of 90° between both components (corresponding to linear polarization).
90° Phase Shift High Reflection Mirrors
The function of the 90º Phase Shift High Reflection mirrors in a high power CO2 laser system is similar to the standard 90º Phase Shift mirrors but has higher reflection resulting in less power loss and increased life expectancy. This is an improvement of our standard 90º phase shift coating; reducing absorption level by 50% and setting it to be lower the 1%. This superior absorption level is achieved with no compromise in the phase shift performance (tolerance +/- 2 degrees) or visible light (630-670 nm) reflection. This coating becomes our standard for 90º phase shift mirrors.
Reflection Spectrum of 90º phase shift Mirrors Coatings