Conversion of radiation from a laser with an unstable resonator using conical optics

The feasibility of reducing the angular divergence of the output radiation from a laser with an unstable resonator by conversion of the cross-sectional profile of the beam using conical optics is discussed. The results of experiments using a $CO_2$-laser are presented. These show that the use of a conical converter at the output of a laser with a low gain (having an unstable resonator with a magnification close to unity) should give an appreciable improvement in the directionality of the radiation.