Abstract: The present invention relates generally to the field of optical devices and particularly to embodiments of a three-stage PPLN optical parametric oscillator/difference-frequency generator configuration. The present invention allows simultaneous generation of three wavelengths in efficient use of the pump signal. The structure of the first embodiment of the present invention comprises a first PPLN element having first and second grating regions, and a second PPLN element having its own grating period. An input coupler is positioned at the input and exit ends of a resonator cavity and the first PPLN element is positioned between the input coupler and the second PPLN element. A second embodiment of the present invention includes a single PPLN element having three separate grating regions. The single PPLN element is positioned between input and output coupler mirrors. A third embodiment of the present invention includes a single PPLN element having three grating regions.