Nonlinear optical properties of lithium niobate crystals doped with alkaline earth and rare earth elements

Nonlinear optical properties of lithium niobate crystals doped with alkaline-earth (Zn2+) and rare-earth (Er3+) elements were quantitatively studied from the chemical bond viewpoint of crystal. The different influences of Zn and Er dopants on the dielectric response of LiNbO3 were compared. The value of nonlinear optical second-harmonic generation coefficients was determined mainly by the Li–O bonds both in LiNbO3:Zn and LiNbO3:Er crystals. We observed sharp changes in the second order nonlinear optical response of Zn-doped LiNbO3 single crystals at 1064 nm with increasing Zn concentration in the crystal. The calculated values of the nonlinear optical coefficients for the LiNbO3:Zn crystals exceed those for the LiNbO3:Er crystals. The LiNbO3:Zn crystal with dopant concentration 5.48 mol.% is the most suitable crystal for the second-harmonic conversion.