PHOTOREFRACTIVE EFFECT IN PERIODICALLY POLED LITHIUM-NIOBATE AND LITHIUM TANTALATE AND IN MGO-DOPED LITHIUM-NIOBATE

Photorefractive effects in the periodically poled lithium niobate(LN) and lithium tantalate(LT) and the MgO-doped LN are examined. Inverse p hotorefractive response (build-up) time versus incident power keeps a linear relationship in row incident power region. The decrease of phot oconductivity is in the sequence of the congruent, the larger-and smal ler-poling period LT. Lower photorefractive effects are found in the p eriodically paled LT with smaller period 10.5 mu m than in that with l arger period 23 mu m, which is owing to effective cancellation of phot ovoltaic current. The higher resistance to photorefractive damage is f ound in the LN doped with 5 mol% MgO and in the periodically poled LN with period 5 mu m, The results are attributed to a reduced photovolta ic current density.