Super-Gaussian output from a cw-CO2 laser by using a graded phase mirror resonator

We have mirror for a resonator having a specified output. 1,2 We have shown that certain optical resonators can have a fundamental mode of a stable type with a large beam waist and, at the same time, higher-order modes with large losses. The design of highly discriminating laser resonators is thus possible. We now present some experimental results for such a custom output laser device. The performances of two resonators have been compared. The graded-phase feedback mirrors are differently designed in order to provide two different super-Gaussian output beams with the following amplitude profiles: exp[−(r/2.5)2] and exp[−(r/3.2)6], where r is the transverse circular coordinate measured in millimeters. The first mirror is of course spherical, and the resonator is semiconfocal. The gain medium is a cw-CO2 circular discharge section of 18 mm of diameter. The maximum monomode power output for the conventional spherical resonator is 5 W. With the graded-phase mirror, increases of monomode power output of 25% have been measured. These observations are in close agreement with theoretical calculations of the efficiency of these resonators, taking into account the saturation. Beam profiles in the near field and far field have been measured and are presented.