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  • Open Access

On-chip microwave interferometry using phononic integrated circuits

Mahmut Bicer, A. Fahad Malik, and Krishna C. Balram*

  • Quantum Engineering Technology Labs and School of Electrical, Electronic and Mechanical Engineering, University of Bristol, Woodland Road, Bristol BS8 1UB, United Kingdom

  • *Contact author: krishna.coimbatorebalram@bristol.ac.uk
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Phys. Rev. Applied 25, 064035 – Published 8 June, 2026

DOI: https://doi.org/10.1103/96ns-kvtd

Abstract

Piezoelectric phononic integrated circuits (PnICs), chip-scale platforms in which GHz frequency acoustic fields are routed in µm-scale waveguide geometries, have steadily advanced in performance and complexity, providing new degrees of freedom for manipulating microwave signals. Here, we consider the use of PnICs for implementing on-chip microwave interferometers (f=3.4GHz) using a gallium nitride (GaN) on silicon carbide (SiC) PnIC platform. We demonstrate controlled mode amplitude splitting, differential control (local phase shift), and mode recombination in an unbalanced (ΔL=1.6mm) phononic Mach-Zehnder interferometer (MZI), achieving a maximum fringe visibility >0.985. The high visibility does not imply high sensitivity due to the presence of parasitic acoustic modes in the MZI. We quantify the effect of these parasitic guided modes in the interferometer, and discuss potential design improvements for achieving quasi-single-mode operation in PnICs, with a view toward enabling applications in microwave and acoustic signal processing and sensing.

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Phys. Rev. Applied 25, 064035– Published 8 June, 2026
  • Received 20 February 2026
  • Revised 30 April 2026
  • Accepted 14 May 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

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