Acoustic Holography and Its Application to the Characterization of a Therapeutic Ultrasound Array

Friday, November 8, 2024, 4:00 p.m. Central Time

Dr. Randall P. Williams
Applied Research Laboratories
The University of Texas at Austin
https://www.arlut.utexas.edu/

Acoustic holography is a technique used to capture the structure of a three-dimensional pressure field using values recorded over a two-dimensional surface.  The two-dimensional representation is referred to as a hologram, and the word “hologram” itself comes from the Greek words for “whole” and “record,” signifying that a 2D hologram is sufficient for capturing the full 3D field.  Acoustic holography has found use in several applications in acoustics including wave field synthesis, surface vibrometry, material characterization, and field characterization.  In the case of nonlinear fields generated by therapeutic ultrasound transducers, focal pressures may be accurately determined using holography when direct measurements using a hydrophone are not accurate due to the presence of shocks at the focus.  In this talk I will present the theoretical background of acoustic holography, practical implementation considerations, and discuss its application to development of a multi-element focused transducer array used for high-intensity therapeutic ultrasound.  I will also provide a brief review of other emerging applications of acoustic holography.

Evaluating the Function of the Human Middle Ear

Friday, November 1, 2024, 4:00 p.m. Central Time

Professor Emeritus Craig A. Champlin
Department of Speech, Language, and Hearing Sciences
The University of Texas at Austin
https://slhs.utexas.edu/faculty/craig-champlin

The middle ear (ME) lies between the visible outer and the inner ear, containing the structures for hearing and balance.  In terrestrial organisms, the ME transfers vibrations from the acoustic environment to the sensory cells in the cochlea.  The mechanisms of the ME help overcome the impedance mismatch between air and the water-filled cochlea.  Moreover, the ME comprises various simple machines that facilitate effective stimulation and, thus, hearing.  The delicate ME structures are vulnerable to disease, trauma, or genetic malformation.  Significantly altering the ME system’s mass and stiffness will affect hearing sensitivity.  Clinical tests of ME function have existed for decades.  Recent technological advances have enabled more accurate, efficient, and comprehensive assessments across the lifespan.  This talk will focus on the mechanics of the typical human ME, representative disorders, and current evaluative methods.

Development of a Borehole Characterization Tool Using Time Reversal and Nonlinear Elastic Wave Spectroscopy

Friday, October 25, 2024, 4:00 p.m. Central Time

Dr. Timothy J. Ulrich
Los Alamos National Laboratory
Texas A&M University
https://engineering.tamu.edu/materials/profiles/ulrich-timothy.html

Understanding material mechanics in the presence of defects is crucial for applications in energy security (oil, gas, geothermal, nuclear fuel disposition), climate change mitigation (CO2 sequestration), and seismic hazard analysis.  These areas span scales from grain-level to fault-scale mechanics, highlighting the need for advanced characterization tools.  A recent collaboration between Chevron Energy Technology Corporation and Los Alamos National Laboratory has resulted in the development of a novel acoustic logging tool designed to enhance rock formation characterization and wellbore integrity evaluation.  This tool combines the power of time-reversal of elastic waves, which enables precise location of wave sources and localization for active interrogation, with nonlinear elasticity techniques, which have demonstrated remarkable sensitivity to damage mechanics across scales from microns to meters and beyond.  The integration of these two approaches significantly enhances the tool’s ability to detect subtle material changes.  In this seminar, the principles of the tool will be introduced, followed by demonstrations of its functionality, the current state of the technology, and future directions.

Know When to Hold Them, Know When to Fold Them: Balancing the Application of Science in the Context of the Human Experiences and Budget
through Acoustics Consulting for the Built Environment

Friday, October 18, 2024, 4:00 p.m. Central Time

Robin Glosemeyer Petrone, Partner
Threshold Acoustics
Chicago, Illinois
https://www.thresholdacoustics.com/robin-glosemeyer-petrone

Acousticians have dedicated years of study to the science of how sound is generated, how it moves through a medium, and how our brain interprets the signal. Yet our practice takes place as one expert in a room among many. Each criterion set to shape the auditory experience occurs in a building that must also hold itself up, allow us to breathe, not catch fire, and, oh yes, look attractive too. All while meeting a budget. As experts, we must often contemplate when to hold fast to our scientific expertise and when to compromise to ensure projects move forward. Beyond Acoustics Consulting for buildings, these lessons apply to any endeavor moving from a singular function into the application of the science in a system

A Waveform Model for Bat Echolocation

Friday, October 11, 2024, 4:00 p.m. Central Time

Stephen P. Blackstock
Applied Research Laboratories
The University of Texas at Austin
www.arlut.utexas.edu

The great majority of bats are known to use active sonar to navigate and forage.  Most biosonar models of bats rely on the correct assignment of an echo from a broadcast signal.  This assignment should pose considerable difficulty for bats in large groups, such as during evening exodus from a large roost, unless bats in swarms employ techniques to avoid or minimize jamming.  Brazilian free-tailed bats (Tadarida brasiliensis) form some of the largest aggregations on the planet and demonstrate flexibility in the spectro-temporal characteristics of their echolocation signals.  We offer a new hypothesis that this species uses subtle variations in these characteristics to facilitate successful echolocation in dense groups.  Testing this hypothesis is facilitated by a compact analytical waveform model of the frequency modulation functions observed in measured bat echolocation signals.  We propose a model based on low-order Chebyshev polynomial series, which we call the Chebyshev Polynomial Series Frequency Modulation (CPSFM) model.  The parameters of this model determine “call signatures,” which may be analyzed to determine their distinguishability.  We analyzed recordings of Brazilian free-tailed bat swarms and fit isolated vocalizations to the CPSFM model.  We show that standard signal detection methods, such as cross correlation and background normalization, enable quantitative estimation of detection performance, including rejection of interfering emissions and echoes.  Results demonstrate that subtle but specific variation in spectro-temporal shape can constitute the basis of call differentiation, which may be an adaptive strategy for bats to reject acoustic signals from conspecifics when echolocating in dense swarms.

Directional Acoustic Transducers

Friday, October 4, 2024, 4:00 p.m. Central Time

Xiaoyu Niu
Chandra Department of Electrical and Computer Engineering
The University of Texas at Austin
https://sites.google.com/site/utacousticmems/

Directional audio has captured interest for decades, yet generating and sensing sound in a specific direction remains challenging.  In this presentation we describe our efforts to prototype a directional microphone and speaker.  First, our directional microphone draws inspiration from the hearing mechanism of the fly Ormia ochracea.  Prototypes fabricated using silicon microfabrication demonstrate the fly’s remarkable sound localization ability.  These prototypes utilize multiple piezoelectric sensing ports to simultaneously transduce two orthogonal vibration modes, allowing for the concurrent measurement of sound pressure and pressure gradient.  An integrated high-impedance preamplifier is included to enhance signal reading, and a specialized package shields against electromagnetic interference.  Second, we explore the well-known parametric array (PA) effect in air using capacitive micromachined ultrasonic transducers (CMUTs).  When the CMUTs are driven with high voltage, the diaphragm undergoes a “collapse” mode, significantly enhancing its swing distance and ensuring phase matching across the array.  We present a small PA prototype using commercial MEMS microphone dies.  Finally, we explore the design of PA directional speakers for consumer electronics using CMUTs.

Comparison of Coaxial Co-Rotating and Counter-Rotating Rotor Acoustics in Hover

Friday, September 27, 2024, 4:00 p.m. Central Time

Professor Jayant Sirohi
Department of Aerospace Engineering and Engineering Mechanics
The University of Texas at Austin
www.ae.utexas.edu/people/faculty/faculty-directory/sirohi

Coaxial co-rotating and counter-rotating rotors can be found on several Urban Air Mobility (UAM) aircraft designs.  The relative direction of rotation of the rotors has a profound effect on rotor loads as well as acoustics.  This presentation will describe an experimental investigation of the acoustics of a hovering coaxial co-rotating rotor and a coaxial counter-rotating rotor.  The rotors have a radius of 1.11 m and were operated at a tip Mach number of 0.40, tip Reynolds number of 765,000 and an axial spacing of 1.55 chord lengths.  The index angle between the upper and lower blades of the stacked rotor was varied.  The overall sound pressure level (OASPL) was found to be significantly larger for the counter-rotating rotor.  For example, total rotor noise at -45 deg angle of elevation was 6 dB greater for the counter-rotating rotor than the co-rotating rotor at 8 deg collective.  These increases in OASPL were driven by large increases in tonal noise for the counter-rotating rotor, of up to 10 dB higher than the co-rotating rotor at some angles of elevation.  This was attributed to additional tonal noise occurring at harmonics of 2N_b/rev, where N_b is the number of rotor blades, due to vibratory loads from 2N_b/rev blade crossings. The results of the experimental study suggest that, in terms of reduced noise and increased hover efficiency, the co-rotating rotor is preferable to the counter-rotating rotor for UAM vehicle configurations that implement compact or closely spaced designs.

Acoustic Waves in Time-Varying and Spatiotemporally-Varying Media

Friday, September 20, 2024, 4:00 p.m. Central Time

Professor Michael R. Haberman
Walker Department of Mechanical Engineering
The University of Texas at Austin
https://www.me.utexas.edu/people/faculty-directory/haberman

Acoustic and elastic metamaterials with time- and space-dependent material properties have recently received attention as a means to generate nonreciprocal wave propagation or to control the frequency and wavenumber of fields scattered by spatiotemporally modulated (STM) boundaries.  This talk begins with an introduction to acoustic wave propagation in materials whose properties are space- and time-dependent, beginning with a cursory summary of wave motion in spatially periodic media.  This is followed by a derivation of coupled constitutive relations for the conservation of momentum and mass in materials with spatiotemporally-varying properties, and examples of reflection and transmission behavior at “time boundaries” are presented. The more general case of spatiotemporally modulated properties is then presented and discussed in the context of nonreciprocal wave propagation. Lastly, the case of scattering from surfaces with spatiotemporally modulated input admittance is considered. It is shown that one may control the frequency and direction of scattered acoustic fields by changing the amplitude and speed of the admittance modulation.  Cases of nonreciprocal and diffusive scattering from the same STM surface with different modulation parameters are then shown and discussed. The talk concludes with a brief discussion of current challenges and future research directions on these topics

Influence of Sample Anisotropy on Angle-Dependent Ultrasonic Reflection Coefficients: A Study Using Synthetic 3D Printed Layered Samples

Friday, September 13, 2024, 4:00 p.m. Central Time

Dr. Daria Olszowska and Professor Carlos Torres-Verdin
Hildebrand Department of Petroleum and Geosystems Engineering
The University of Texas at Austin
pge.utexas.edu/facultystaff/faculty-directory/torres-verdin

Anisotropy has a significant impact on the elastic and mechanical properties of rocks.  Misidentifying a rock formation as isotropic can result in significant errors when predicting stress distribution and mechanical deformation in the subsurface.  Sandstone-shale laminated rocks are intrinsically anisotropic and are of great interest in subsurface engineering applications as they constitute important assets in the global oil and gas reserves.  Under specific conditions (layer thickness, property contrast), these rocks can be effectively represented by an equivalent homogeneous transversely isotropic (TI) medium.  Elastic moduli of the TI medium are calculated as the product of the properties of each layer and their respective thickness.  We examine the latter through laboratory testing and via angle-dependent ultrasonic reflection-coefficient measurements.  Experimental data acquired from synthetic 3D-printed layered samples with varying layer thicknesses (greater, similar, or smaller than the receiver size) are compared to semi-analytical and numerical simulations.  This comparative analysis yields valuable insights into the resolution of the method and helps to determine the conditions under which spatially heterogeneous samples can be accurately represented by effective-medium models of elastic rock behavior. 

Laboratory findings acquired in a controlled environment confirm that samples characterized by weak anisotropy and layer thickness smaller than the receiver diameter can be accurately represented by an equivalent vertical transversely isotropic medium.  Noteworthy differences arise when measurements are taken parallel and perpendicular to the sample bedding plane.  Measurements acquired perpendicular to layering reflect the properties of the effective medium.  Reflection coefficients acquired parallel to the layers can effectively capture the elastic properties of the layer with differences below 5% compared to the homogeneous material.

A Career in Underwater Acoustics at Applied Research Laboratories, UT Austin

Friday, September 6, 2024, 4:00 p.m. Central Time

Dr. Marcia J. Isakson
Director, Signal and Information Sciences Laboratory
Applied Research Laboratories
The University of Texas at Austin
www.arlut.utexas.edu

Underwater acoustics is a vibrant field with applications in ocean remote observations, national security, climate change monitoring and ecosystem sensing. This talk will focus on a career in underwater acoustics at Applied Research Laboratories, The University of Texas at Austin (ARL:UT). ARL:UT is the University Affiliated Research Center at UT Austin with a diverse portfolio supporting the Department of Defense and the US intelligence community. An introduction to ARL:UT will be given with a discussion of one career path at the lab. Next, an introduction to underwater acoustics will be presented followed by some insight into where the field is headed for the next few decades.

Scalable Simulation of High-Frequency Wave Propagation

Friday, April 19th, 2024, 4:00 p.m. Central Time

Jacob Badger
Oden Institute
The University of Texas at Austin
https://www.oden.utexas.edu/people/directory/Jacob-Badger/

Developing fast and scalable solvers for high-frequency wave propagation is a notoriously difficult problem in mathematics and scientific computing. One challenge is that classical numerical discretizations yield indefinite discrete systems that preclude use of classical scalable solvers. Simulation of high-frequency wave propagation has thus been limited to problems on the order of 1 billion degrees of freedom (DOFs). This talk outlines a novel scalable and efficient multigrid solver for high-frequency wave propagation problems. The solver is based on the discontinuous Petrov–Galerkin (DPG) finite element method and is demonstrated to solve wave propagation problems in acoustics, electromagnetics, and elasticity with complex geometries, high-contrast heterogeneous media, and other challenging features. Scaling is demonstrated to nearly 1 trillion DOFs, an unprecedented scale in high-frequency wave simulation.

Spatiotemporally-Resolved Kinematic and Stress Measurements of Interfacial Cavitation in Soft Matter

Friday, April 12th, 2024, 4:00 p.m. Central Time

Professor Jin Yang
Department of Aerospace Engineering and Engineering Mechanics
The University of Texas at Austin
https://www.ae.utexas.edu/people/faculty/faculty-directory/yang

Inertial cavitation is a common phenomenon found in nature and many engineering systems. When harnessed carefully, laser or ultrasound-focused, energy-driven cavitation can be a very beneficial tool in a wide range of medical and materials applications, including laser surgery, lithotripsy, drug delivery, and, more recently, soft material characterization. In this talk, we will begin by describing our recent developments in the material property characterization method, called Inertial Microcavitation Rheometry (IMR), to investigate laser-induced inertial cavitation (LIC) in soft matter, where the surrounding material is subjected to ballistic and ultra- high strain rates (103 ∼ 108s−1). Through IMR, we can precisely quantify the nonlinear viscoelastic, finite deformation constitutive behavior of soft materials at ultra-high strain rates. At such high rates, we will also show soft hydrogels and biological materials might exhibit significant strain-stiffening effects, dynamic surface instabilities, and fracture patterns. Following this, I will present our recent findings on the dynamics of laser-induced inertial cavitation (LIC) near the gel-water interface. Historically, studies of cavitation dynamics at liquid-solid interfaces were limited to observations of surface deformations and cavitation bubble morphology due to challenges in measuring subsurface behavior. However, understanding the intricate dynamics of cavitation at these interfaces holds significant implications for engineering and medical applications. For the first time, we provide high-fidelity and high-throughout full-field measurements on the spatiotemporal deformation behavior and wave propagation within soft materials near interfaces due to laser-induced inertial cavitation at extremely high rates. Our results provide critical insights into how soft biological tissues respond to the immense forces generated by the violent collapse of a cavitation event. These measurements will be particularly useful for minimizing collateral damage to non-target tissues in cavitation-based medical therapies.

The Acoustics and Psychoacoustics of the JFK Assassination

Friday, April 5th, 2024, 4:00 p.m. Central Time

Professor Dennis McFadden
Ashbel Smith Professor Emeritus in Experimental Psychology
The University of Texas at Austin
https://liberalarts.utexas.edu/psychology/faculty/dm8797

This talk is unusual for this audience because it covers US history as well as acoustics and psychoacoustics. In 1978, the US House Select Committee on Assassinations (HSCA) conducted a partial re-enactment of the 1963 assassination of President John F. Kennedy in Dealey Plaza, Dallas, Texas. One goal was to measure the acoustics existing at various locations around the plaza in response to rifle shots from the 6th floor window of the building housing the Texas School-Book Depository and from behind the fence on the grassy knoll. On the basis of those measurements, the physical acoustics team concluded that there were four gunshots and two assassins, not three gunshots from one assassin as was concluded by the Warren Commission in 1964. The HSCA’s four-shot conclusion soon was proved wrong, for reasons that will be discussed. I was a member of the team responsible for making psychoacoustical observations from various locations around Dealey Plaza during the re-enactment rifle shots in 1978. One goal was to determine why earwitnesses to the JFK assassination did not agree about the location of the gunman. To be discussed are the acoustical and psychoacoustical factors making it difficult for people to localize a rifle firing supersonic rounds in an echoic environment. No evidence supporting any of the common alternative theories of the assassination was obtained.

Acoustic Emissions-based Rodent Behavior Analysis

Friday, March 8th, 2024, 4:00 p.m. Central Time

Dr. Shivashankar Peruvazhuthi
Maseeh Department of Civil, Architectural and Environmental Engineering
Center for Learning and Memory, Department of Neuroscience, (collaboration)
The University of Texas at Austin
https://sites.google.com/view/ssrg/home?authuser=0

Over the past few decades, capturing and analyzing acoustic emissions (AE) from processes such as corrosion and crack propagation has been vital to characterize their effect on the integrity of structures. My research, too, is based on the AE technology, but instead of studying structural integrity, I take a deeper look at the behavior of rodents using AE generated by the animal. In the tests, mice were introduced, one at a time, in an open-field arena with an aluminum plate as the floor. As the rodent moved around this open field, its voluntary and involuntary movement applied subtle forces to the aluminum plate, leading to the generation of Lamb and Shear horizontal (SH) waves in the plate. The generated waves were detected with ultrasonic sensors (attached to the plate’s bottom), and acquired by treating the animal as an acoustic source and the generated waves as Acoustic Emissions. The generated waves, i.e., the acquired AE, contain information about the rodent’s physiology, behavior, and underlying mental states and offer a new modality to investigate the animal’s behavior. Two types of tests were undertaken in the open field, one in which the animal was allowed to move and behave freely without any external stimulus, and one in which a loud tone was played to evoke an acoustic startle response. Results from these studies demonstrated the potential of the AE technology to enhance rodent behavior analysis, with the possibility of identifying hidden behavioral modules and tracking behavioral differences due to genetic differences, prior experiences, and neural manipulations.

Nonclassical Nonlinear Acoustics of Structured Media

Friday, March 1st, 2024, 4:00 p.m. Central Time

Professor Lev A. Ostrovsky
University of Colorado, Boulder
https://www.colorado.edu/amath/lev-ostrovsky

In this presentation we outline the area of “nonclassical nonlinear acoustics” related to many solid materials with a complex structure, such as grainy media, concrete, and various kinds of rock. Such media are characterized by (i) strong elastic nonlinearity, (ii) stress-strain hysteresis, and (iii) a long-time recovery after an impact (“slow dynamics”). The latter can take hours in laboratory samples and years after earthquakes. Our theory is based on the physics of grain contacts. In particular, the slow recovery is described by an Arrhenius-type equation commonly used for chemical reactions. Earlier we proposed a physical model of granular materials with an inter-grain contact potential that includes adhesion and an elastic (Hertz) force. After an initial impact, the recovery occurs irreversibly, with hysteresis, whereas some contacts remain in the “excited,” metastable state, and then slowly (commonly logarithmically in time) return to the initial state due to thermal processes. The slow dynamics are described by an Arrhenius-type equation commonly used for chemical reactions. In this presentation, the state of the problem is outlined, and new developments are discussed. Particularly, the data of logarithmic soil recovery, which can take years after strong earthquakes, are discussed and described using the theory. In conclusion, some yet unsolved problems are indicated.

Wireless E-Tattoos for the Mobile Tracking of Cardiovascular Health

Friday, February 23rd, 2024, 4:00 p.m. Central Time

Professor Nanshu Lu
Department of Aerospace Engineering and Engineering Mechanics
The University of Texas at Austin
https://sites.utexas.edu/nanshulu/

The research objective of my research group is to bridge humans and robots through soft electronics. We have developed skin-soft, hair-thin, and skin-conformable electronic tattoos (e-tattoos) for human body digitization, as well as stretchable electronic skins (e-skins) that can mimic the softness and sensations of human skin. This talk will focus on two different types of wearable e-tattoos for continuous and ambulatory cardiovascular health monitoring. The first one is a chest-laminated trimodal e-tattoo that can synchronously and simultaneously perform electrocardiography (ECG), seismocardiography (SCG) and plethysmography (PPG). This trimodal chest e-tattoo can provide a comprehensive monitoring of the electrical and mechanical and activities of the heart, as well as the perfusion of blood to the skin, out of which various cardiac time intervals and cardiac output can be extracted, even during light movements. We are also exploring the possibility of using a PPG sensor array for differentiating arterial vs. venous oxygenation. The second one is a wearable low-power ultrasound e-tattoo, which is a work in progress. While ultrasound is a promising modality to capture absolute hemodynamic metrics, state-of-the-art wearable ultrasound sensors are still constrained by bulky and complex back-end control and data acquisition systems. Our innovative analog-edge-computing method of hemodynamic feature detection can dramatically reduce power consumption, computational costs, and sensor size, enabling wireless implementation. The ultimate goal of this line of research is to paint a full picture of one’s cardiovascular health in real-time through a multimodal, distributed, and noninvasive e-tattoo body sensor network.

Distilling the Acoustics from Multi-Rotor Platforms Using New Methods in Signal Processing.

Friday, February 16th, 2024, 4:00 p.m. Central Time

Dr. Charles E. Tinney
Applied Research Laboratories
The University of Texas at Austin
https://www.arlut.utexas.edu

In a recent article by Tinney, Zhao-Dubuc, and Valdez (International Journal of Aeroacoustics, 2023, DOI: 10.1177/1475472X231199186), proper orthogonal decomposition (POD) and the Vold-Kalman order tracking filter (VKF) were combined to evaluate the most energetic signals in the sound field of a coaxial, corotating rotor in hover. The method comprised a covariance matrix for the POD problem that was constructed using auto- and cross-spectral densities of a stationary sensor set. The POD technique isolates structures in space while VKF methods filter structures in time. The current study reconsiders the same unique combination of analysis techniques, but develops the framework using a different form of the covariance matrix for occasions when the stationary sensor set is large, or when a spectral domain representation of the signals is not necessary. As such, this defaults to the conventional form of Lumley’s POD. The combined use of these techniques (conventional POD with Vold-Kalman filters) is then exercised using the same database of the sound-field generated by a coaxial, corotating rotor in hover to study the effect that changes to the rotor index angle has on the sound directed at listeners located below the rotor disk plane. Filtered acoustic waveforms are extracted using the first four spatial POD modes and VKF phasors associated with the first four rotor blade-pass frequency harmonics; these filtered signals are responsible for the impulsive like signatures that drive community annoyance. An assessment of the trade-space between these filtered waveforms and the rotor’s aerodynamic performance demonstrates that an 8% shift in rotor figure of merit is obtainable without changing the sound pressure levels generated by the stacked rotor. Alternatively, 6.3 dB and 4.0 dB reductions in sound pressure levels propagating along the rotor disk plane and below, respectively, can be achieved without any changes to rotor performance.

In Situ Measurements of Sediment Compressional and Shear Wave Speed from the New England Mud Patch and Shelf Break Areas
Using the Acoustic Coring System

Friday, February 2, 2024, 4:00 p.m. Central Time

Dante D. Garcia
Applied Research Laboratories
The University of Texas at Austin
https://www.arlut.utexas.edu

In situ measurements of geoacoustic properties provide direct characterization of the seabed at near ambient conditions. The Acoustic Coring System (ACS) is a gravity corer equipped with acoustic probes that obtains in situ compressional wave (30–200 kHz) and shear wave (400–1200 Hz) measurements as the corer penetrates the seabed. During the April 2022 R/V Endeavor coring survey, the ACS was deployed at 36 locations within the New England Mud Patch (NEMP) and New England Shelf Break areas. Data from these experiments were analyzed to characterize the depth-dependent structure of the seabed geoacoustic properties as well as their spatial variability. The in situ measurements are interpreted in the context of stratigraphic layering measured by a seismic survey. Depth-dependent profiles of compressional wave speed from a subset of these deployments in the NEMP are compared to profiles previously collected at nearby locations in 2016. In situ compressional wave records from both areas are compared with ex situ sediment core measurements, including data collected from core loggers and laboratory analyses. Additionally, novel in situ shear wave speed measurements from the NEMP and surrounding areas are introduced.

Integrated Optomechanical Systems for Sensing and Communications

Friday, January 26, 2024, 4:00 p.m. Central Time

Dr. Jason J. Gorman
Physical Measurement Laboratory
National Institute of Standards and Technology
https://www.nist.gov/people/jason-j-gorman

Optomechanical resonators that combine low-loss micromechanical resonators and optical microcavities have been shown to provide exquisite sensitivity to changes in the effective cavity length and exhibit complex nonlinear behavior that can be controlled optically. To date, the focus for optomechanical resonators has been on fundamental physical measurements under well-controlled laboratory conditions. In this presentation, I will describe our efforts to use integrated optomechanical resonators for more applied measurements, with the prospect of significantly improving resolution and accuracy compared to traditional technologies, such as microelectromechanical sensors. Examples will include an optomechanical accelerometer that provides high precision, low-uncertainty measurements without calibration, a phononic-photonic crystal resonator developed for quantum-limited force detection, a pulsed laser interferometer that has been used to measure vibrations out to 12 GHz for applications in mobile communications filters and quantum acoustic devices, and a high-overtone bulk acoustic resonator designed for microwave-to-optical frequency conversion.