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 (k²) operating in the C-band, as a solution to meet the needs of next-generation high-speed communications. Firstly, the k² achievable for first-order modes in different orientations of Y-cut LiNbO3 substrates is explored, showing the best combination of A1 modes in the X-axis direction in 128° Y-cut LiNbO3. 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 k² of 57% is demonstrated by optimizing the electrode arrangement, exceeding the state-of-the-art.