Numerical studies on hybrid resonators for a medium-sized chemical oxygen iodine laser

Abstract

Off-axis negative-branch and off-axis positive-branch hybrid resonators, suitable for a laser with large medium cross section and a small output coupling are explored numerically. The basis of our theory is the Fresnel-Kirchhoff integral equation and the calculations describe a passive resonator. With respect to mirror tilting, the calculations confirm that in the unstable direction, the off-axis negative-branch resonator is less sensitive to mirror misalignments than the off-axis positive-branch one. In the stable direction, the sensitivity to mirror misalignment is larger than in the unstable direction and is dependent on the mirror curvature. The fabrication of cylindrical mirrors for such hybrid resonators is difficult, and deviations in mirror radius of curvature are possible. The effects of such deviations are addressed. Near the nominal mirror parameters, the off-axis negative-branch unstable resonator is insensitive to mirror curvature variations if the resonator length is appropriately adapted to the mirror curvatures.