Abstract: Tunable light sources having a single optical parametric generation (OPG) source that results in an amplified, narrow bandwidth seed beam and methods of tuning therewith are disclosed. The tunable light source may include a polarization rotator to rotate a pump beam before a first pass through an OPG, and a linear-to-circular polarization device to polarize the pump beam directed back toward the OPG for a second pass therethrough. Alternately, the tunable light source may include an OPG source through which a pump beam passes only in the first direction, a separator that separates a signal beam from the pump beam exiting from the OPG, a narrowband wavelength filter that receives the signal beam and generate a seed beam, and a reflecting surface that directs the seed beam back through the OPG (opposite the first direction) to seed the back part of the pulse of the pulse laser.