Triangular laser resonators with astigmatic compensation

The magnitudes and locations of the beam waists in both the sagittal and the tangential planes have been found by means of the ABCD matrix method for a triangular resonator. Equilateral and isosceles resonators are discussed, and curves are given from which resonators with astigmatism-free beams can be designed. A frequency-doubled triangular Nd ring laser has been constructed after this design, and it is demonstrated that this laser emits a single longitudinal mode with a circular TEM(00) Gaussian beam.