Silicon-Based Highly c‑Axis-Oriented Strontium Barium Niobate Films with Large Pockels Coefficients

To develop a new generation of high-performance silicon-based electro-optic modulators, it is necessary to find an electro-optic crystal with a simple fabrication process, stable chemical properties, and large Pockels coefficients, such as strontium barium niobate (Sr _x Ba_1-x Nb₂O₆, SBN). In this work, potassium-doped Sr_0.75Ba_0.25Nb₂O₆ and sodium-doped Sr_0.75Ba_0.25Nb₂O₆ buffers were fabricated on SiO₂ via the sol-gel method, followed by the deposition of Sr_0.75Ba_0.25Nb₂O₆ (SBN75) films using radio frequency magnetron sputtering (RFMS). This sequential processing enabled the realization of SBN75 films exhibiting a c-axis preferential orientation. Lattice mismatch is not a limiting factor in this approach. Furthermore, the extracted Pockels coefficient r ₃₃ of highly c-axis-oriented SBN75 films reached a maximum value of 431.3 pm/V, which is 10 times larger than that in lithium niobate (LN). The aforementioned findings make SBN75 a promising candidate for compact and high-speed electro-optic modulators.