  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.
