Composition dependence of the electro‐optic properties of iron‐doped lithium niobate crystals mounted as bulk modulator.

In this contribution, we report a complete set of electro‐optic coefficients of iron‐doped lithium niobate as function of the composition varying from sub‐congruent to near‐stoichiometric in a series of four crystals. The concentration of iron is constant for all crystals of the series. The electro‐optic measurements of the r22 and rc coefficients were performed on a Sènarmont ellipsometric setup while those of r13 and r33 were performed on a Mach‐Zehnder interferometric setup, by adaptation of the same frequency doubling electro‐optic modulation and the MDM methods implemented in both electro‐optical arrangements. The corresponding dielectric permittivities ε11 and ε33 as a function of composition were also determined. All electro‐optic coefficients reveal a small change with composition, but significant above the experimental error. The nonmonotonous dependences of all electro‐optic coefficients are found to be closely linked to their corresponding dielectric permittivities. The EO coefficients of iron‐doped lithium niobate crystals as function of the composition. [ABSTRACT FROM AUTHOR]