Thermal Modulation of Gigahertz Surface Acoustic Waves on Lithium Niobate

TL;DR

This paper presents integrated thermo-acoustic modulators on lithium niobate platforms that control gigahertz surface acoustic waves via local heating, enabling reconfigurable microwave signal processing with high phase shifts.

Contribution

It introduces a novel thermo-acoustic modulation technique on lithium niobate platforms, achieving large phase shifts and amplitude modulation for SAWs at gigahertz frequencies.

Findings

Achieved over 720 degrees phase change with 2.6 deg/mW efficiency on bulk lithium niobate.

Demonstrated amplitude modulation using acoustic Mach-Zehnder interferometers.

Enabled reconfigurable acoustic signal processing for wireless and microwave systems.

Abstract

Surface acoustic wave (SAW) devices have wide range of applications in microwave signal processing. Microwave SAW components benefit from higher quality factors and much smaller crosstalk when compared to their electromagnetic counterparts. Efficient routing and modulation of SAWs are essential for building large-scale and versatile acoustic-wave circuits. Here, we demonstrate integrated thermo-acoustic modulators using two SAW platforms: bulk lithium niobate and thin-film lithium niobate on sapphire. In both approaches, the gigahertz-frequency SAWs are routed by integrated acoustic waveguides while on-chip microheaters are used to locally change the temperature and thus control the phase of SAW. Using this approach, we achieved phase changes of over 720 degrees with the responsibility of 2.6 deg/mW for bulk lithium niobate and 0.52 deg/mW for lithium niobate on sapphire. Furthermore, we demonstrated amplitude modulation of SAWs using acoustic Mach Zehnder interferometers. Our thermo-acoustic modulators can enable reconfigurable acoustic signal processing for next generation wireless communications and microwave systems.