MECHANISM TRANSITION OF SELF-PUMPED PHASE-CONJUGATION IN KTA1-XNBXO3-FE CRYSTALS

Mechanism transitions of Self-Pumped Phase Conjugation (SPPC) with wav elength and doping concentration are observed in KTN:Fe (KTa1-xNbxO3:F e with x = 0.48) crystals. The SPPC mechanism in KTN:Fe (0.4 wt.%) cry stal transforms from ''Stimulated Photorefractive Backscattering and F our-Wave Mixing'' (SPB-FWM) to ''cat'' (or total internal reflection) as the wavelength increases from 514.5 nm to 620 mm. SPPC at 514.5 nm is formed with the ''cat'' mechanism in a 0.2 wt.% doped KTN:Fe crysta l, while with the SPB-FWM mechanism in a 0.4 wt.% doped one. These mec hanism transitions are discussed with respect to the dependence of the backscattering gain coefficient of the crystals on wavelength and dop ing concentration.