Publications
Non-Contact Characterization of Plates Using a Turbulent Air-Jet Source and an Ultrasound Microphone
Published in MDPI NDT, February 1 2026
We report on the non-contact characterization of various plate materials (including aluminum and steel) using a high-pressure, micrometer-scale air jet as a broadband ultrasound source and an optomechanical microphone as a receiver. Through-plate transmission spectra are dominated by zero-group-velocity (ZGV) Lamb modes. We attribute this to the ‘point-like’ nature of both the source and receiver, since ZGV modes are spatially localized and comprise a range of non-normal wave numbers. As is well known, the properties of the ZGV modes, including their frequency and amplitude, are sensitive to thickness variations or the presence of defects. The continuous nature and high acoustic power of the gas jet source enabled us to perform uninterrupted scanning of non-uniform steel plates. Given the ubiquitous and low-cost nature of compressed air systems, our approach might be of interest for the rapid inspection of industrial parts.
Resonant Ultrasound Spectroscopy Detection Using a Non-Contact Ultrasound Microphone
Published in MDPI Sensors, October 4 2025
We observed vibrational eigenmodes for a variety of millimeter-scale objects, including glass and sapphire lenses, by placing them on a piezoelectric ‘shaker’ driven by a broadband noise or frequency sweep signal, and using an optomechanical microphone to pick up their vibrational signatures emitted into the surrounding air. High-quality vibrational modes were detected over the ~0–8 MHz range for a typical object–microphone spacing of 1–10 mm. The observed eigenfrequencies are shown to be in excellent agreement with numerical predictions. Non-contact detection of resonant vibrational eigenmodes in the MHz ultrasound range could find application in the quality control of numerous industrial parts, such as ball bearings and lenses.
Characterization and Localization of Micro-Scale Gas Leaks Using an Optomechanical Ultrasound Sensor
Published in The Journal of the Acoustical Society of America, July 11 2025
This preprint explores how optomechanical sensors can detect high-frequency acoustic emissions from micro-scale gas leaks, even from holes as small as 5 µm. By capturing the full broadband spectrum of turbulent jet noise—including frequencies beyond the range of conventional ultrasonic microphones—the study demonstrates that these sensors can identify leak rates as low as ~10⁻³ Pa·m³/s. The findings highlight the promise of broadband, high-sensitivity “acoustic sniffer” tools for quantitative leak detection in energy systems and industrial processes.
Coupling the Thermal Acoustic Modes of a Bubble to an Optomechanical Sensor
Published in Microsystems & Nanoengineering, 26 December 2024
This work explores the unique interactions between an optomechanical sensor and air bubbles in water, revealing thermal acoustic modes of bubbles, including higher-order resonances previously only theorized. The study also demonstrates the elastic Purcell effect, where the bubble environment modifies the sensor’s vibrational spectrum, leading to frequency-dependent enhancement or suppression of mechanical motion. These findings deepen our understanding of bubble acoustics and open new avenues for microfluidics, biosensing, and fundamental acoustic research.
Air-Coupled Ultrasound Using Broadband Shock Waves from Piezoelectric Spark Igniters
Published in Applied Physics Letters, 21 August 2024
This paper investigates the generation and transmission of broadband, air-coupled ultrasound using low-cost piezoelectric spark igniters. By employing an optomechanical microphone, the team detected high-amplitude shock pulses with frequencies extending beyond 5 MHz—achieving exceptional signal-to-noise ratios without the need for precise alignment. These results highlight the potential of simple spark-based ultrasound sources combined with compact, sensitive receivers for non-contact characterization of solid materials in air.
Spectroscopy of Substrate Thermal Vibrational Modes Using an Optomechanical Sensor
Published in Optical Materials Express, 12 June 2024
This research explores how optomechanical sensors can detect the natural vibrational modes of their own fused silica substrates. By coupling substrate modes with an optomechanical sensor—enhanced by ethylene glycol droplets—the team achieved high-fidelity recordings of substrate vibrations over a broad frequency range (0–40 MHz). The findings demonstrate the potential for optomechanical sensors to probe substrate thermal vibrations and highlight opportunities for using these modes to improve mechanical resonator performance or as information channels in phononic networks.
Ultrasonic Spectroscopy of Sessile Droplets Coupled to Optomechanical Sensors
Published in Lab on a Chip (Royal Society of Chemistry), 26 October 2023
This study introduces a novel method for analyzing the acoustic properties of sub-nanoliter liquid samples using integrated optomechanical sensors. By depositing sessile droplets onto these sensors, the system passively detects thermally driven acoustic modes within the droplets. The observed resonant features, some hybridized with the sensor’s vibrational modes, align closely with theoretical predictions across a 0–40 MHz frequency range. This technique offers a promising approach for precision acoustic sensing in small-volume biological and chemical samples.
Observation of Thermal Acoustic Modes of a Droplet Coupled to an Optomechanical Sensor
Published in Applied Physics Letters (AIP), 26 July 2023
This paper reports the first observation of thermally driven acoustic modes in a water droplet coupled to a high-sensitivity optomechanical sensor. Using a microfabricated optical resonator, the system detects naturally occurring acoustic oscillations excited by thermal fluctuations. This work advances our understanding of fluid–structure interactions at microscale and demonstrates the potential of optomechanical sensors for non-contact acoustic characterization of soft matter systems.
All-Optical, Air-Coupled Ultrasonic Detection of Low-Pressure Gas Leaks and Observation of Jet Tones in the MHz Range
Published in Sensors (MDPI), 15 June 2023
This study demonstrates a fully optical, air-coupled ultrasonic sensing system capable of detecting low-pressure gas leaks and capturing high-frequency jet tones up to several MHz. Unlike traditional acoustic sensors, the system offers contactless measurement, high sensitivity in ambient air, and robustness against electromagnetic interference. The method proves effective for monitoring transient leak events and flow anomalies in industrial settings, providing a new standard for non-invasive leak detection and acoustic diagnostics.
Ultrasound Sensing at Thermomechanical Limits with Optomechanical Buckled-Dome Microcavities
Published in Optics Express (2022)
This paper presents a novel approach to ultrasound sensing that operates at the thermomechanical noise floor using optomechanical buckled-dome microcavities. By leveraging high mechanical quality factors and exceptional optical sensitivity, the researchers demonstrate pressure detection capabilities at the fundamental noise limit. The technique shows promise for compact, chip-integrated ultrasonic sensors that outperform conventional piezoelectric transducers, especially in high-frequency applications requiring extreme precision.
Whitepapers
Ultrasonic Gas Leak Detection Using BROADSONIC Optical Ultrasonic Sensing
Published by Ultracoustics Technologies Ltd., February 24, 2026
Pressurized gas leaks in industrial and commercial equipment are a significant source of fugitive methane
emissions and a safety hazard. Small leaks at pipe fittings, valve packings, and compressor seals often go
undetected because they produce no visible sign and their audible hiss is masked by ambient noise. Conventional
detection methods such as handheld combustible gas detectors and soap bubble testing require close proximity,
are slow to deploy across large facilities, and provide no quantitative data about leak severity.
BROADSONIC: Revolutionizing Partial Discharge Detection in Electrical Systems
Published by Ultracoustics Technologies Ltd., January 25, 2024
This white paper introduces BROADSONIC, an innovative optical acoustic sensor designed to detect partial discharges (PD) in high-voltage electrical systems with exceptional sensitivity and immunity to electromagnetic interference. Traditional acoustic sensors often face challenges related to limited bandwidth and susceptibility to EMI, hindering their effectiveness in PD detection. BROADSONIC addresses these issues by employing an optical detection method that offers a wide bandwidth and high sensitivity, enabling the detection of subtle discharge events at significant distances.
Air-Coupled Wall Thickness Measurement for NDT Applications
Published by Ultracoustics Technologies Ltd., October 2, 2023
This white paper introduces a non-contact method for measuring wall thickness in non-destructive testing (NDT) applications using air-coupled ultrasonic sensing. By eliminating the need for couplants or direct contact, this approach is particularly beneficial in scenarios where traditional methods are impractical, such as weld inspections, pipe wall thickness measurements, and semiconductor quality control. The technique involves generating an ultrasonic pulse within the material, which reflects back and is detected by a highly sensitive optical sensor. Despite significant attenuation at the air-material interface, the system’s exceptional sensitivity enables accurate thickness measurements. The paper includes experimental data demonstrating the method’s efficacy and discusses its potential applications across various industries.