The present invention relates generally to an apparatus that increases the conversion efficiency of optical parametric oscillators and also reduces overall system size and susceptibility to vibration. The first embodiment of the present invention incorporates a PPLN OPO architecture (20) which includes mirrored coatings (32, 36) on the entry surface area (22) and exit surface area (24) of a monolithic nonlinear optical medium (26). The coatings (32, 36) act as mirrors, however, the mirrors are actually affixed to the PPLN element (28, 30). In the first embodiment of the present invention, the PPLN element (26) is a dual grated element. The second embodiment of the present invention uses a single grated PPLN element.