Periodic UV erasure of the nonlinearity for quasi-phase-matching in optical fibers

Summary form only given. Summmary form only given. Recently more than 20% efficient second-harmonic generation (SHG) and parametric fluorescence from periodically poled optical germanosilicate fibers were reported, opening new prospects for the realization of second-order nonlinear optical processes in all-fiber devices. In both cases the fiber samples were thermally poled, subjected to a periodic electric field (periodic thermal poling, PTP), generated by the anodic electrode which had been photolitographically defined on the flat side of a D-shape optical fiber. The field periodicity induced a periodic second-order nonlinearity (/spl chi//sup (2)/), necessary for quasi-phase-matching (QPM). We report on a new technique, periodic UV erasure of second-order nonlinearity (PUESN), which presents a few important advantages over PTP: device lengths of /spl sim/1 m or more can be obtained by scanning the UV beam through and amplitude mask over the uniformly poled fiber; much shorter periods can be achieved by using a phase mask to create UV interference fringes, thus making in principle possible more complicated and finer patterns for example for backward parametric interactions; also a fairly complex photolitography process can be skipped altogether.