PHASE RETARDER FOR TRANSFORMATION OF POLARIZATION OF HIGH-POWER INFRARED-LASER BEAMS BASED ON RESONANT EXCITATION OF SURFACE ELECTROMAGNETIC-WAVES ON METALLIC DIFFRACTION GRATINGS

We report a new method for the highly efficient transformation of a li near polarized laser beam into a beam with any required polarization. The physics of polarization conversion is based on resonant excitation of surface electromagnetic waves (SEWs) on metallic gratings with per iod d approximately lambda (where lambda is wavelength of light) and s ubsequent SEW rescattering into the direction of specular reflection. The parameters of such gratings (period, depth, and groove profile) ar e calculated by means of the developed simple analytical theory. The g rating phase retarders with reflectivity R=92 to 97% for transformatio n of linearly polarized CO2 and CO laser beams into a circular polariz ed beam are fabricated. The efficiency of these phase converters inclu ded in a 1.5-kW CO2 laser technology system for metal cutting is demon strated. The converters essentially enhance the quality and velocity o f cutting and their high strength to resist optical damage is shown.