Abstract

A new type of toric concave mirror laser resonator with a big Fresnel number is presented. The $M^2$ factor of an output laser beam of the new resonator with a Fresnel number of 8.05 is close to that of the plane-concave stable resonator with a Fresnel number of 2.01, the volume of output mode of the new resonator is about four times of that of the plane-concave stable resonator. A $3.2\mathrm{kW}$ doughnutlike laser beam with an $M^2$ factor of 1.9 is obtained experimentally by using the new resonator on a high-power transverse flow $\mathrm{C}{\mathrm{O}}_2$ laser, while the similar laser power with an $M^2$ factor of 7.5 is obtained by using a plane-concave stable resonator with the same Fresnel number. Results show that a toric concave mirror laser resonator can permit operation of the laser with high power and high beam quality mode in the laser with large gain volume.

© 2009 Optical Society of America

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