Generation of a single-cycle surface acoustic wave pulse on LiNbO3 for application to thin-film materials

Abstract

Surface acoustic wave (SAW) technology has been explored in thin-film materials to discover fundamental phenomena and to investigate their physical properties. It is used to excite and manipulate quasiparticles such as phonons or magnons and can dynamically modulate the properties of the materials. In the field, SAWs are typically excited by a continuous wave at a resonant frequency. Recently, generation of a single-cycle SAW pulse has been demonstrated on GaAs substrate. Such a SAW pulse provides a potential to access a single quasiparticle excitation and to investigate its dynamics by time-resolved measurements. On the other hand, to modulate and control the properties of thin-film materials, it is generally required to generate high-intensity SAWs. In this work, we demonstrate the efficient generation of a SAW pulse using a chirp interdigital transducer (IDT) on LiNbO3 substrate. We have fabricated chirp IDT devices with bandwidths from 0.5 GHz to 5.5 GHz. We also confirmed the generation of a SAW pulse with 0.3 ns full width at half maximum by performing time-resolved measurements. The conversion efficiency between input power and SAW on LiNbO3 substrate is approximately 45 times larger than that on GaAs substrate. This enables us to generate a high-intensity SAW pulse, meeting the requirement for the modulation of thin films. Our results will expand the research in the field, such as spintronics and magnonics, and lead to their further advancements.