We describe a technique to integrate embedded microelectrodes and optical waveguides in Lithium niobate (LiNbO 3 ) using a femtosecond laser, and a Y-splitter modulator was demonstrated. The Y-splitter was fabricated by femtosecond laser direct writing and the embedded microelectrodes were fabricated by combining femtosecond laser ablation with selective electroless plating. The embedded microelectrodes give rise to homogeneous electric field across the optical waveguides, which could result in

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... effective electro-optic overlap. The simple and flexible technique could open new opportunities for fabricating integrated 3D electro-optic devices.