A1-Mode Lamb Wave Resonator in 128° Y-Cut Lithium Niobate with Electromechanical Coupling Coefficient of 57%

This paper reports an acoustic resonator with a high electromechanical coupling coefficient (k<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) operating in the C-band, as a solution to meet the needs of next-generation high-speed communications. Firstly, the k<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> achievable for first-order modes in different orientations of Y-cut LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> substrates is explored, showing the best combination of A1 modes in the X-axis direction in 128° Y-cut LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>. Then by optimizing the geometry design, a Lamb wave resonator with excellent performance was fabricated. The device in this work excites first-order asymmetric (A1) Lamb wave mode in the 128° Y-cut lithium niobate film. A high k<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 57% is demonstrated by optimizing the electrode arrangement, exceeding the state-of-the-art.