Method of calculating the alignment tolerance of a Porro prism resonator

A method of calculating the angular alignment tolerance of a Porro prism laser oscillator is presented. The reduction in mode volume due to misalignment is found by a ray optical approach. An analytical expression for alignment tolerance, in terms of resonator length L, prism azimuth angle theta, rod location L(2), and rod aperture radius alpha is obtained. An experiment was set up to measure the laser output reduction due to reflector tilting. Results obtained are in good agreement with the theoretical predictions.