Electro‐optic modulation and self‐poling in strain‐induced waveguides in barium strontium titanate niobate

Characterization of bulk single crystals and optical waveguides in Ba1−xSrxTiyNb2−yO6 (BSTN) indicate it to be a promising new ferroelectric material for electrooptic devices. The electro‐optic coefficient r33 is measured to be 218±12 pm/V, a factor of 7 greater than LiNbO3. Data on refractive indices, dielectric constant, and Curie temperature Tc in bulk samples are also presented. Strain‐induced waveguides in Z‐cut samples exhibited low losses (1.8 dB/cm for TM polarization and 2.5 dB/cm for TE polarization) at a wavelength of 1.3 μm. Electro‐optic modulation was demonstrated in these waveguides to frequencies ≳100 MHz. A ‘‘self‐poling’’ effect was found, whereby strong electro‐optic modulation is observed in the strain waveguides without repoling the crystal after processing at temperatures far above Tc.