New radio-frequency resonators based on periodically poled lithium niobate thin film and ridge structures

In this paper, we present new results on the development of an original acoustic waveguides concept based on a Periodically Poled Lithium Niobate transducer. Periodically poled transducers have been investigated recently as an alternative to classical inter-digital transducers for the excitation and detection of guided acoustic waves. We expose here two different structures of RF resonators based on this concept: a “Silicon/Gold layer/PPLN thin film/Gold layer/Silicon” stack and a PPLN-ridge structure. Simulations, fabrication and experimental results of both resonators are presented. “Si/10 μm-thick PPLN/Si” and “PPLN-ridge (11 μm-wide and 250 μm-deep)” resonators with a poling period of 50 μm have been achieved. The experimental admittances of these devices have pointed out the existence of an isolated mode operating at frequencies near 110 MHz for the stack structure and near 160 MHz with an electromechanical coupling of about 19 % for the ridge structure. These results are in agreement with the finite and boundary elements simulations.