arXiv subjects

Matt Eichenfield

Publications and source records attributed to Matt Eichenfield.

At least 19 recordsLinked to original sources

arXiv2026

Optomechanical transducers for gigahertz frequency ultrasound imaging

Ultrasound is a noninvasive, real-time, and therefore widely used imaging modality; yet its application in cellular and sub-cellular biology is significantly limited by rapidly increasing acoustic losses in aqueous solutions with decreasing wavelength. Here we introduce a nano-optomechanical cavity transducer platform to generate and detect ultrasound in aqueous solutions with a sub-micron acoustic wavelength. We analyze the full signal pathway through a combination of finite element method modeling and the coupled differential equations that describe the dispersive optomechanical interaction. Our findings project a signal-to-noise ratio in the thousands at ~5 GHz, limited by diffraction losses and thermal-acoustic noise. This work establishes a viable path towards optomechanical ultrasound systems capable of label-free imaging at cellular and sub-cellular length scales while also providing a broader framework for optomechanical crystal device operation in aqueous environments relevant to biochemical sensing, medical diagnostics, underwater acoustic sensing, and nanoscale imaging.

physics.optics↗

arXiv2026

Acoustoelectrically enhanced acousto-optic modulation in an integrated silicon nitride and thin film lithium niobate platform

Acoustoelectric interactions in piezoelectric-semiconductor heterostructures allow the propagation characteristics of microwave frequency phonons in piezoelectric media to be controlled and radically enhanced, providing electrically controllable phonon gain, large velocity tuning, isolation, and circulation, as well as extremely large electron-mediated phononic nonlinearities. Here, for the first time, we create such a piezoelectric-semiconductor heterostructure with lithium-niobate-on-insulator and InGaAs that also supports guided optical modes through the addition of a silicon nitride waveguide and modification of the acoustic materials to provide an optical lower cladding. We use this new architecture to demonstrate acoustoelectrically enhanced acousto-optic modulation, where 1 GHz phonons are piezoelectrically generated and acoustoelectrically amplified on-chip by up to 60 dB before impinging on the optical waveguide, providing pure phase modulation with a $V_πL$ figure-of-merit of 0.077 V-cm while only consuming 3.77 mW of DC electrical power to provide the amplification. We then consider future applications enabled by these functionalities and describe a novel tunable optical delay and an optoelectronic oscillator (OEO) analog---an acoustoelectrically enhanced opto-acoustic oscillator (AE-OAO). We show that using Brillouin optomechanical transduction and acoustoelectrically lossless acoustic time delay, the AE-OAO could replace kilometers of optical fiber delay used in OEOs but on a single, centimeter-scale chip.

physics.optics↗

arXiv2026

Mode-selective acousto-electric modulation of phonons in a silicon photonic platform

Acousto-electric (AE) interactions enable electrical control of acoustic propagation through piezoelectric media. Bringing AE control onto integrated photonic platforms provides a powerful on-chip control mechanism to reconfigure both the acoustic propagation through piezoelectric media. Bringing AE control onto integrated photonic platforms provides a powerful on-chip control mechanism to reconfigure both the acoustic delay line response and the effective photon-phonon interaction by electrically tuning the phonon propagation. Here we report a mode-selective AE modulation effect in a scalable aluminum nitride on silicon-on-insulator (AlN-on-SOI) platform. An applied DC field is seen to modulate the phonon dissipation via changes in carrier concentration in a mode-selective fashion, producing up to 20 dB forward transmission suppression of non-fundamental modes within an acoustic delay line while maintaining the fundamental Rayleigh mode, a phenomenon not captured by conventional AE treatments. To probe these dynamics, we integrate an optical waveguide along the acoustic delay line, providing a broadband, non-destructive interface between the acoustic and optical domains. Leveraging both this optical interface and the underlying mode selectivity, we demonstrate proof-of-concept multi-domain transduction and Rayleigh-mode filtering on this hybrid platform, outlining a scalable path toward electrically reconfigurable mode engineering and microwave-photonic functionality.

physics.optics↗

arXiv2026

Resonant multi-harmonic acousto-optics for programmable frequency control of visible light in a CMOS platform

Scaling quantum control for atoms, ions, and solid-state emitters requires gigahertz-frequency spectral control of high-power visible light in a volume-manufacturable platform. Silicon nitride photonics provides high power handling and CMOS-foundry compatibility but has no intrinsic mechanism for high-speed modulation. Integration with piezoelectric materials enables acousto-optic phase modulation, and mechanical resonant enhancement has made it efficient at gigahertz frequencies. However, a single resonance restricts the modulation waveform to a single tone, imposing Bessel-function sideband amplitudes and limiting frequency-shifting efficiency to 33.9%. Here we engineer a silicon nitride acousto-optic microstructure to support harmonically spaced resonances at 1.14 GHz and 2.28 GHz, each strongly optomechanically coupled to a 730 nm guided optical mode, so that tailored non-sinusoidal modulation waveforms can be resonantly synthesized. By piezoelectrically controlling the two mechanical amplitudes and their relative phase, we demonstrate 50% conversion to one sideband (1.5x the single-tone theoretical maximum), a flat seven-line comb, and a frequency shift with 60 dB carrier and 53 dB image suppression - to our knowledge the highest reported for an integrated modulator. The devices are fabricated in a 200 mm CMOS foundry, and we measure 91.7% yield without post-fabrication tuning across 36 devices from three wafers. We also show how the technique can be straightforwardly scaled to three or more harmonics. This result overcomes the trade-off between resonant enhancement and spectral programmability, with important consequences including improved single-qubit gate efficiency for hyperfine qubits.

physics.optics↗

arXiv2026

Ultra-low loss piezo-optomechanical low-confinement silicon nitride platform for visible wavelength quantum photonic circuits

Realizing photonic quantum computing at scale requires integrated circuits that combine ultra-low loss with fast, low-power, low-hysteresis, and low-crosstalk reconfiguration. These requirements are particularly challenging at visible wavelengths, where many quantum resource-state generators, including single-photon sources and quantum memories, naturally operate. Low-confinement silicon nitride waveguides offer the requisite loss performance, but conventional thermo-optic modulators dissipate significant static power, driving thermal crosstalk and precluding cryogenic operation. Visible-wavelength piezo-optomechanical circuits avoid these drawbacks, but existing demonstrations rely either on high-confinement waveguides with propagation losses of 35-100 dB/m, or on low-confinement platforms using foundry-incompatible PZT. Here we combine piezo-optomechanical actuation with a CMOS-foundry-fabricated, low-confinement silicon nitride platform, achieving 2.6 dB/m propagation loss at 780 nm, megahertz-scale modulation bandwidth, a half-wave voltage-length product of 2.8 Vm, and negligible hysteresis. We demonstrate reconfigurable Mach-Zehnder interferometers with 0.63 dB loss per spiral phase shifter, enabling deep, actively reconfigurable visible-wavelength quantum photonic circuits.

physics.optics↗

arXiv2026

Strategic Plan for Neutral Atom Quantum Computation

We present a strategic plan for neutral atom quantum computation, bringing together hardware development and theory advancements to achieve the goal of practical quantum advantage. The concept of practical quantum advantage is defined, along with how to verify claims of advantage, and approaches to designing quantum algorithms that deliver practical advantage. Future directions for neutral atom quantum processor hardware are described: scaling-up system size, Qubit encodings and atomic platforms, going further below threshold with neutral-atom logical-qubit performance, continuous reloading of qubits, and fast readout. We also explore opportunities for scalable integrated photonic control technologies. Alongside hardware advancements, new developments in quantum error correction and compilation of quantum circuits are proposed. Finally, we examine the opportunity of networking multiple neutral atom quantum processors together to perform distributed quantum computing and overcome possible limitations of a single system.

quant-ph↗

arXiv2026

Micro-electromechanical photonic integrated memristors

Programmable optical memristors embedded in photonic integrated circuits (PICs) are emerging as an important technology for high-speed optical storage and in-memory optical computing applications. These devices provide multi-level, non-volatile storage of optical phases that can be interrogated at the speed of light, enabling parallel data readout or energy-efficient multiply-accumulate operations in artificial neural networks. However, there remains several outstanding challenges with existing optical memristor technology including durability, material-induced optical losses, large-scale reconfigurability, or fabrication yield for realistic applications. Here we introduce an analog-programmable photonic memristor based on photonic integrated micro-electromechanical (MEMS) cantilevers produced in a CMOS foundry. The memristor consists of low-loss silicon nitride waveguides, requires no additional back-end materials integration, and is all electrically programmed with electrostatic-piezoelectric forces. We demonstrate up to 5-bit phase storage levels, 50 kbit/s programming speeds, strain-assisted non-volatility lifetimes >1 hour, >1 billion cycle endurance, and stress-tested millions of write-read cycles with pseudorandom bit sequences. We further extend the memory lifetime to several days with simple electronic refresh circuits in a portable battery-powered module, demonstrating a proof-of-concept optical random-access memory in static or dynamic configurations. Our MEMS-photonics technology represents an important step toward practical optical memristors.

physics.optics↗

arXiv2026

Towards a monolithic platform for coupling superconducting circuits to low-loss microwave phonons in AlScN on 4H-SiC

Hybrid superconducting-phonon quantum processing is promising for cavity QED, measurement-based quantum computing, and other quantum applications. Relative to microwave photons at the same frequency, phonons can provide ultra-compact footprints, extremely low losses, and greater connectivity. Phonons can also couple strongly to superconducting circuits through the piezoelectric effect. However, this promise rests on scalable platforms that achieve these benefits without degrading superconducting circuit performance. This motivates a monolithic platform combining low phononic loss, strong electromechanical coupling, and superconducting-circuit compatibility without requiring suspended phononics. Here, we characterize a monolithic quantum acoustic platform combining aluminum superconducting circuits on exposed silicon carbide (SiC) with piezoelectric aluminum scandium nitride (AlScN) on SiC for integrated phononics. This architecture is enabled by selective removal of AlScN from selected chip regions, allowing aluminum superconducting microwave resonators to be fabricated directly on the SiC while preserving adjacent AlScN-on-SiC regions for phonon transduction. The resulting Al-on-SiC resonators exhibit a coherent lifetime of 2.9 μs, demonstrating compatibility with aluminum superconducting quantum devices. In parallel, cryogenic surface acoustic delay-line measurements on the retained AlScN-on-SiC regions show low phononic propagation loss at 4.05 GHz, corresponding to an estimated phonon lifetime of 7.6 μs. Together with a previously demonstrated electromechanical coupling coefficient of about 4.3% and a theoretical upper bound of 8%, these results establish Al-on-SiC/AlScN-on-SiC as a promising monolithic platform for integrating superconducting microwave circuits with piezoelectric phononic components for quantum acoustic networking and hybrid quantum systems.

quant-ph↗

arXiv2026

Nonequilibrium thermodynamics of the acoustoelectric quantum vacuum

The quantum vacuum can assume thermal properties as a consequence of system kinematics, highlighting the nuance of our definition of particles in quantum field theory. Here, we explore this phenomenon in acoustoelectric systems, involving the interaction of phonons and plasmons, where the charge carriers drift at a constant velocity exceeding the speed of sound. Through an open quantum systems analysis, we show that the acoustoelectric quantum vacuum acquires a thermal character with a temperature defined by the drift velocity and the phonon wavevector. Realistic parameters yield effective temperatures of several Kelvin, establishing acoustoelectric systems as a promising platform for the investigation of quantum vacuum effects.

quant-ph↗

arXiv2026

Monolithic Integration of Piezo-Optomechanical Photonics and CMOS Electronics

Next-generation photonic architectures for AI, sensing, and quantum computing require thousands to millions of reprogrammable photonic devices on a chip[1]. The monolithic integration of Electronically-backed Photonic Integrated Circuits (EPICs) allows for very high density electrical interconnection and electronic drivers that can scale with photonics. Piezo-optomechanical photonic integrated circuits (POMPICs) offer low power consumption, high speed modulation, cryogenic compatibility and broadband optical transparency from ultraviolet to infrared wavelengths[2,3], but have not been demonstrated with monolithically integrated CMOS electronics. Here, we show a fully monolithic, all-CMOS fabricated platform for POMPICs co-fabricated with commercial control electronics. 200 millimeter photonic wafers are constructed directly on completed CMOS driver wafers by back-end-of-line processing, connecting integrated piezoelectric actuators under broadband silicon nitride waveguides to a high-density digital backplane comprising >2 million electrical connections per die with 6.4x6.4 micron electrode pitch. We introduce segmented POMPIC components as Photonic Digital-to-Analog converters (PDACs) that convert low-voltage digital electronic signals to multi-bit analog optical phase and amplitude modulation, and we demonstrate parallel control of optical phase shifters, Mach-Zehnder interferometers, optical routing trees, and tunable ring resonators using a standard HDMI interface to program CMOS electronics. We test multiple reticles and perform electronic and photonic characterization across the entire wafer to establish uniformity and yield, demonstrating wafer-scale integration of POMPICs on an electronic backplane and enabling dense, scalable electronic control of piezo-optomechanical circuits.

physics.optics↗

arXiv2026

Quantum-Limited Acoustoelectric Amplification in a Piezoelectric-2DEG Heterostructure

We provide a quantum mechanical description of phonon amplification in a heterostructure consisting of a two-dimensional electron gas (2DEG) stacked on top of a piezoelectric material. An applied drift voltage effectively creates a population inversion in the momentum states of the 2DEG electrons, giving rise to spontaneous emission of phonons. Once an acoustic wave is launched, the pumped electrons release phonons via stimulated emission, returning to depleted ground states before being pumped back to the excited states. We show that whereas efficient amplification using a 1D electron gas requires the acoustic wavelength to roughly equal the average electron-electron spacing, a 2DEG enables efficient amplification for any wavelength greater than the average electron-electron spacing. We derive the imaginary and real parts of the 2DEG first-order acoustic susceptibility as functions of electronic drift velocity in specific limits and derive the gain per unit length for the signal and the quantum noise, with the gain matching the classical result in the short-electronic-lifetime (low-mobility) regime. Moreover, we analyze the gain clamping due to pump depletion and calculate the maximum achievable intensity. Our results provide a framework for designing novel acoustic devices including a quantum phononic laser and phase-insensitive quantum phononic amplifiers.

cond-mat.mes-hall↗

arXiv2026

Noise factor of Brillouin amplifiers

Stimulated Brillouin scattering (SBS), an optical nonlinearity arising from photon-phonon interactions, has formed the basis for a large class of optical signal processing devices, including Brillouin amplifiers. A limiting factor of such amplifiers is the noise due to thermal-mechanical fluctuations that the phonons imprint on the optical signal. Prior work has either inferred or experimentally observed a noise factor ($F$) that depends only on the thermal occupation of the phonons ($F\approx 1+n_{th}$). We show that this noise factor results naturally from a Hamiltonian-based spatio-temporal coupled mode treatment in the limit of large Brillouin amplification and when phonon propagation is neglected. Moreover, this theoretical framework allows us to extend our treatment to a much larger and more representative parameter space for emerging SBS systems; specifically, this analysis accounts for the forward or backward nature of the scattering process and the effects of phonon propagation, optical loss, and small Brillouin gains. Our results demonstrate that the noise factor can deviate radically from $F\approx 1+n_{th}$ for a host of modern SBS devices, especially those in which phonon propagation significantly changes the coupled mode dynamics.

physics.optics↗

arXiv2026

Noise and dynamics in acoustoelectric waveguides

We present a quantum field theoretic formulation of acoustoelectric interactions in waveguide-like systems of arbitrary cross-section. Building on an open quantum systems approach, we derive a unified description of plasmon-phonon coupling that incorporates dissipation, noise, and the influence of drift currents. Our analysis captures both bulk and surface plasmon modes, highlighting how drift currents Doppler-shift plasmonic resonances and reshape the phonon noise spectrum. The resulting Heisenberg-Langevin equations yield closed-form expressions for frequency shifts, gain, and noise power spectra, enabling direct evaluation of performance metrics such as the noise factor in acoustoelectric amplifiers and oscillators. In the appropriate limits, this framework reproduces known results while extending them to complex geometries.

physics.optics↗

arXiv2026

Exact Solutions to Acoustoelectric Interactions in Arbitrary Geometries

Acoustoelectric interactions occur when free carriers in a semiconductor interact with the fields of an acoustic wave in a piezoelectric medium. These interactions can amplify acoustic waves, as well as give rise to extremely large phononic nonlinearities and strong non-reciprocal effects. The field of acoustoelectric devices is currently dependent on analytical and perturbative solutions for the two simplest arrangements of piezoelectric-semiconductor materials. While these canonical models have allowed the field to advance substantially, new geometries are arising that do not satisfy assumptions integral to these models. These assumptions include the treatment of the interactions between the acoustic fields and free carriers as weak, the neglect of the tensorial nature of the material properties, the omission of the spatial variations in the phonons' electric field profiles, and the disregard of elastic coupling across material boundaries, among others. We develop, for the first time, a finite element method (FEM) model to solve for acoustoelectric interactions in arbitrary geometries that avoids making the assumptions of the canonical models. We verify the FEM model using results for amplification, dispersion, and non-reciprocity obtained from the canonical models in their regime of validity. We then examine the acoustoelectric effect in two geometries not covered by the canonical models: a thin piezoelectric film placed on a semiconductor substrate and a fully 2D waveguide under a thin semiconductor layer. This work lays the foundation for accurate modeling of arbitrary acoustoelectric geometries such as those currently being developed for all-acoustic radio frequency (RF) signal processing, acoustoelectrically enhanced photonic devices, and quantum acoustoelectric devices.

physics.app-ph↗

arXiv2025

Hybrid electrostatic-piezo MEMS photonic integrated modulators

Programmable photonic integrated circuits (PICs) have recently emerged as an important technology for quantum information science and artificial neural networks. In particular, PICs with MEMS-based modulators have the advantages of voltage-based control, ultra-low-energy consumption, cryogenic compatibility, and CMOS-foundry support. Here we report a cantilever optical modulator that utilizes hybrid piezoelectric and electrostatic tuning forces together on a monolithic silicon nitride (SiN) PIC platform. The device achieves actuation of visible-wavelength light with quasi-static tuning up to 10 kHz at 1.5 Vπ-cm as well as high-speed (>20 MHz) AC modulation with dynamically adjustable (25 - 40 MHz) mechanical resonances. We report the physics of how geometric nonlinearities such as capacitive pull-in give rise to suspended and contacted cantilever modes. These reversible operating regimes generate different strain profiles and boundary conditions which are responsible for the active tuning of the mechanical resonances. Our proof-of-concept electrostatic-piezo modulator shows promising potential in large-scale programmable PICs applied to high-speed optical switching and optomechanical sensing.

physics.optics↗

arXiv2025

An integrated photonics platform for high-speed, ultrahigh-extinction, many-channel quantum control

High-fidelity control of the thousands to millions of programmable qubits needed for utility-scale quantum computers presents a formidable challenge for control systems. In leading atomic systems, control is optical: UV-NIR beams must be fanned out over numerous spatial channels and modulated to implement gates. While photonic integrated circuits (PICs) offer a potentially scalable solution, they also need to simultaneously feature high-speed and high-extinction modulation, strong inter-channel isolation, and broad wavelength compatibility. Here, we introduce and experimentally validate a foundry-fabricated PIC platform that overcomes these limitations. Designed for Rubidium-87 neutral atom quantum computers, our 8-channel PICs, fabricated on a 200-mm wafer process, demonstrate an advanced combination of performance metrics. At the 795 nm single-qubit gate wavelength, we achieve a mean extinction ratio (ER) of 71.4 $\pm$ 1.1 dB, nearest-neighbor on-chip crosstalk of -68.0 $\pm$ 1.0 dB, and -50.8 $\pm$ 0.2 dB after parallel beam delivery in free-space. This high-performance operation extends to the 420 nm and 1013 nm wavelengths for two-qubit Rydberg gates, showing ERs of 42.4 dB (detector-limited) and 61.5 dB, respectively. The devices exhibit 10-90% rise times of 26 $\pm$ 7 ns, achieve dynamic switching to -60 dB levels within microsecond timescales, and show pulse stability errors at the $10^{-3}$ level. This work establishes a scalable platform for developing advanced large-scale optical control required in fault-tolerant quantum computers and other precision technologies.

quant-ph↗

arXiv2025

Towards Navigation-Grade and Deployable Optomechanical Accelerometry

We design and experimentally demonstrate an architecture for achieving navigation-grade, fiber-packaged optomechanical accelerometers that can operate with a large dynamic range, over a wide temperature range, and without sophisticated laser sources. Our accelerometer architecture is based on a novel set of design principles that take advantage of the strengths of optomechanical accelerometry while eliminating many of its historical weaknesses. Displacement readout is provided by an integrated, differential strain-sensing Mach-Zehnder interferometer (DSMZI) attached to an ultra-rigid, bulk-micromachined proof mass having a 93.4 kHz fundamental resonance frequency (22.5 pm/g displacement). Despite the extreme rigidity, the high displacement sensitivity provides an insertion loss limited 4.2 $μg/\sqrt{\mathrm{Hz}}$ acceleration resolution, with a straight-forward path to achieving 330 $n g/\sqrt{\mathrm{Hz}}$ by improving the fiber-to-chip coupling. Further, we show that the combination of high rigidity and intrinsic differential optical readout makes the device insensitive to the common causes of bias instability, and we measure a bias instability of 6.3 $μg$ at 243 seconds. The DSMZI provides a 17 nm optical bandwidth and a temperature operating range of greater than 20 $^\circ\mathrm{C}$, both orders of magnitude larger than previous demonstrations of optomechanical accelerometers. The high rigidity and large optical bandwidth yield an expected dynamic range of 165.4 dB. The combination of high acceleration resolution, high dynamic range, low bias instability, and intrinsic insensitivity to wavelength, temperature, and package stresses makes our device well suited for deployment in realistic environments demanded by real-world applications and demonstrates a path for optomechanical accelerometers to ultimately exceed the performance of all other chip-based accelerometers.

physics.optics↗

arXiv2025

CMOS-fabricated ultraviolet light modulators using low-loss alumina piezo-optomechanical photonic circuits

Ultra-violet (UV) and near-UV wavelengths are necessary for many important optical transitions for quantum technologies and various sensing mechanisms for biological and chemical detection. However, all well-known photonic platforms have excessively high losses in the UV, which has prevented photonic integrated circuits (PICs) being used to address these and other important application spaces. Photonic waveguides using low-loss alumina cores have emerged as a promising solution because of almunia's large optical bandgap and the high quality of films enabled by atomic layer deposition. However, to the best of our knowledge, active alumina PICs have only been realized using thermo-optic tuning, which precludes switching speeds shorter than one microsecond, high circuit densities, and cryogenically compatible operation. Here, we introduce a CMOS-fabricated, piezo-optomechanical PIC platform using alumina waveguides with low optical losses at UV wavelengths and aluminum nitride piezoelectric strain actuators, which solves the issues associated with thermal tuning. We demonstrate a high-performance, reconfigurable optical filter operating at wavelengths as low as 320 nm. The filter has a 6 nanosecond switching time, a loaded linewidth of 3.3 GHz, tuning rate of -120 MHz/V, and a hold power less than 20 nW.

physics.optics↗