A rod of solid state gain material centered between two flat end mirrors (i.e. the flat-flat resonator) is a common laser resonator configuration. Positive dioptric power in the rod, thermally induced by the pumping of the gain medium, enables the resonator to operate in the stable regime. A typical problem that may ultimately limit maximum power in lasers of this type is the susceptibility of the cavity end mirrors to laser-induced damage. A technique that mitigates this damage by increasing the intra-cavity spot width at the end mirror location is described. The resulting modified resonator is equivalent to the flat-flat resonator with regard to its output laser beam propagation parameters and to the symmetrical mode fill of the gain medium.