Dispersion-induced generation of higher order transversal modes in singly-resonant optical parametric oscillators

We study the effects of higher order transversal modes in a model of a singly-resonant OPO, using both numerical solutions and mode expansions including up to two radial modes. The numerical and two-mode solutions predict lower threshold and higher conversion than the single-mode solution at negative dispersion. Relative power in the zero order radial mode ranges from about 88% at positive and small negative dispersion to 48% at larger negative dispersion, with most of the higher mode content in the first mode, and less than 2% in higher modes.Comment: 13 pages, 4 figures, PACS Numbers: 42.65.Ky, 42.10.Qj, Key Words: parametric oscillation, phase-matching, diffractio