Control of transverse mode pattern in a helium-neon laser using the cat's eye cavity

This paper introduces an innovative method to control and select transverse mode pattern in a He-Ne laser. The cat's eye cavity is established by using a cat's eye reflector as the reflecting mirror. Laser transverse mode pattern varies continuously when the distance between the convex lens and the concave mirror is changed, which form the cat's eye reflector. By Newton-Cotes method, the numerical solution of two-dimensional diffraction integral equation in the cat's eye cavity is obtained, the laser operating modes under various parameters are analyzed, and the eigenvalue ηmn and diffraction power loss corresponding with every transverse mode are calculated. The parameters assuring fundamental transverse mode output are figured out, which match the experiment results well. Therefore, a new convenient real-time means for the control and selection of the laser transverse mode is realized.