Development of an optical resonator with conical retroreflector for generation of radially polarized optical beam - art. no. 687207

Optical resonator for generation of high-power radially polarized beam is presented. In laser cutting applications, radially polarized beam is advantageous because the beam contacts the cut front always with the highly absorptive p-polarization. The proposed resonator comprises a reflector unit that has three conical faces with polarization sensitive dielectric coating, and an ordinary output coupler. The resonator is compatible with any existing circular mirror standing-wave optical resonators. Numerical simulation shows good polarization selectivity with only 1% of reflectivity difference between p and s polarizations, and M-2 factor of the output beam is 1.9. No output power degradation is seen compared to the standard spherical mirror resonator. Design and fabrication of the resonator for a 1kW-class commercial cw CO2 laser is discussed.