arXiv subjects

Scott B. Papp

Publications and source records attributed to Scott B. Papp.

At least 19 recordsLinked to original sources

arXiv2026

Nanophotonic dispersion engineering in tantala-based microresonators with ultralow-loss claddings

Integrated photonics optimized to leverage low loss, nonlinear-optical processes and optoelectronic integration requires robust optical cladding materials and associated fabrication process flows. We develop low-loss silicon dioxide (SiO$_2$) claddings with tantalum pentoxide (Ta$_2$O$_5$, tantala) integrated photonics to realize robust, high intrinsic quality factor ($Q_i$) microresonators and photonic-crystal resonators (PhCRs) for soliton microcomb generation. Specifically, we introduce a full-wafer, low-temperature process compatible with two tantala-based films: pure tantala and an amorphous metal-oxide mixture of titanium dioxide (TiO$_2$, titania) and tantala. Combining tantala with titania enhances the film's resistance to damage from the SiO$_2$ cladding deposition process, offering access to high $Q_i$ above $4 \times 10^6$ in fully cladded microresonators. Our platform supports low-loss edge couplers, group-velocity dispersion engineering by waveguide geometry, access to nanophotonic structures particularly to control phase-matching, and high dimensional tolerance in devices across an entire wafer. Using the platform, we explore the generation of high-efficiency, dark-soliton microcombs with repetition frequency from 50 GHz to 500 GHz, which supports applications such as photonic artificial intelligence acceleration, electronic signaling, and optical data communication.

physics.optics↗

arXiv2026

Photonic-Crystal Microresonator Frequency Combs in the O-band

Photonic-crystal microresonators (PhCRs) are a powerful platform for generating Kerr frequency combs. Because Kerr-soliton dynamics in PhCRs are largely decoupled from the operating wavelength, the comb output can be engineered through customization of the device layer. Here, we demonstrate a tantalum pentoxide (tantala) PhCR platform that supports 1310 nm and 1550 nm band operation, and we explore high-efficiency O-band soliton microcombs with all-semiconductor laser pumps. We engineer the PhCRs with silicon dioxide cladding and normal dispersion with intrinsic quality factors exceeding $7\times10^{6}$. By pumping bandgap modes, we obtain robust and efficient soliton comb formation at a 200 GHz mode spacing. Our PhCRs enable systematic tuning from narrowband to broadband comb states within a single device geometry. The combs exhibit low relative intensity noise approaching the shot-noise limit, indicating stable phase-matching in the PhCR. Using a second resonator coupler, we amplify the comb output off-chip, demonstrating a pathway to high-power O-band sources. These results establish PhCR engineering in the tantala platform as a scalable approach to wavelength-agile, low-noise microcombs for applications in communications, sensing, and signaling.

physics.optics↗

arXiv2026

Induced Directional Switching of Platicon Microcombs in Photonic Crystal Ring Resonators

Microcombs in normal-dispersion photonic crystal ring resonators (PhCRs) are a versatile building block for next-generation integrated photonic circuits, yet they inherently suffer from a directional bias that favors backward-propagating states. This necessitates bulky, non-integrated optical circulators for comb extraction, creating a significant bottleneck for full on-chip integration. In this work, we demonstrate a deterministic method to control and reverse this directionality through Side-mode Induced Forward Forcing (SIFF). By engineering auxiliary mode splittings on resonances adjacent to the pump, we show that the nonlinear dynamics can be steered to favor stable, forward-propagating platicon states. We establish an optimal synchronization condition between the pump and side-mode coupling rates that ensures forward-comb dominance across a wide parameter range. Our findings, validated both numerically and experimentally, provide a critical pathway for circulator-free, integrated normal-dispersion microcombs, offering a scalable architecture for compact telecommunications and sensing systems.

physics.optics↗

arXiv2026

A Scalable All-to-All Reconfigurable Ising Solver Using Pulsed Time-Division Multiplexing

Physics-based computing platforms, such as those based on the Ising model, are an important pillar of future hardware systems built for the artificial intelligence (AI) era. Such platforms show promise for solving nondeterministic polynomial (NP) time problems that are difficult for traditional processing units to solve efficiently as problem size grows. Here, we present a scalable optoelectronic Ising machine architecture, demonstrated with 64 all-to-all connected spins using pulsed time-division multiplexing. The 65 nm CMOS Ising chip integrates the coupling and nonlinear mechanisms in an active area of 3.1 mm2, eliminating the need for benchtop equipment within the loop. The feedback loop of the Ising machine is closed using a compact high-bandwidth, low-loss optical fiber, seamlessly combining optical scalability with the ultradense reconfigurability of integrated electronics. The chip operates at 1 GHz with 4-bit coupling weights and is benchmarked with NP-complete Boolean satisfiability problems consisting of three literals (3-SAT) and clause-to-variable ratios of 32/32, 40/24, and 48/16. Nanosecond annealing times represent at least a three order-of-magnitude improvement over previously reported all-to-all connected works. Time and energy to solutions for 100% 3-SAT clause accuracy are as low as 7.4 us and 2.9 uJ, respectively, achieving more than an order-of-magnitude decrease in time and energy to solution compared to the state of the art. All-to-all connection is demonstrated using MaxCut problems with 100% graph densities. The chip's ability to effectively solve 2-, 3-SAT, and MaxCut problems highlights its reconfigurability and versatility. Furthermore, combining mature CMOS integration with scalable photonic links allows for significant reduction in computation time and energy, addressing the pressing requirements of AI and future hyperscale datacenters.

physics.optics↗

arXiv2026

A generative pre-trained transformer with Kerr-soliton attention

Artificial intelligence systems, particularly through generative pre-trained transformers (GPTs), have enabled capability-rich language models, but their operation incurs substantial costs in digital computation, memory, and data movement. Attention is a core operation in GPTs that computes context-dependent weights for input tokens. Since deep-learning models are defined by compositions of nonlinear transformations, identifying physical systems that can realize them offers a pathway to higher efficiency. Here, we introduce Kerr-soliton attention, harnessing driven-dissipative nonlinear dynamics in a resonator to realize, execute, and validate a deep-learning attention operation in physical hardware. We train a transformer language model using an analytic Kerr-soliton attention response and explore generative inference by streaming model-produced inputs through the experimental system. We observe high-fidelity agreement between the experimentally produced nonlinear weights and those predicted by the analytic Kerr-soliton model. Computation proceeds through streaming-in-time excitation of an ensemble of Kerr solitons, with inputs encoded as temporal signals that evolve under nonlinear dynamics. Our approach maps memory and compute onto the same physical dynamics, relaxing the need for intermediate digital storage and reducing data movement. This work points toward hybrid digital-physical learning systems in which Kerr solitons provide physical memory and high-bandwidth streaming nonlinear processing within deep-learning models.

physics.optics↗

arXiv2026

Integrated ytterbium gain for visible-near-infrared photonics

Rare-earth gain media form the foundation of modern optical communications, emerging quantum hardware, and ultrafast optics. While chip-scale integration can enable fiber-like, and potentially beyond-fiber, functionality with unprecedented scalability, development in the visible and near-infrared remains in its early stages. Here, we demonstrate ytterbium-based optical gain integrated into an aluminum oxide photonic platform, achieving both single-mode lasing and optical amplification in the near-infrared regime. This platform delivers optical amplification with output powers exceeding 0.5 W, an optical-to-optical conversion efficiency above 70%, and a noise figure of 3.3 dB, approaching the quantum limit for phase-insensitive amplification. Furthermore, we achieve femtosecond pulse amplification to a record peak power of 14 kW, enabling supercontinuum generation with visible dispersive waves extending from 780 to 476 nm in conjunction with nonlinear photonic devices. This platform is compatible with heterogeneous integration into standard photonic circuits, laying the foundation for scalable visible-near-infrared photonic systems, including coherent laser arrays, mode-locked lasers, optical clocks, and microwave oscillators.

physics.optics↗

arXiv2026

Nanophotonic control of collective many-body states in Kerr solitons

Spatially periodic systems of coupled bosons are governed by on-site interactions and tunneling between sites, opening a rich phase space of many-body behavior. Here, we explore nanophotonic control of collective many-body light states in a driven-dissipative Kerr microresonator. We demonstrate a non-equilibrium Mott insulator to superfluid transition that arises from the interplay of spatially local Kerr interactions that generate and mediate interference among discrete frequency modes. A photonic-crystal (PhC) lattice bandgap inscribed on the resonator controls linear mode coupling while preserving self-mode Kerr interactions. By increasing the PhC bandgap, we suppress nonlinear cross-mode coupling to access the Mott-insulator phase, wherein the soliton spectrum forms a flattop frequency comb with large and uniform power per mode. In contrast, reducing the PhC bandgap restores cross-mode coupling and drives a delocalized superfluid regime characterized by long-range phase coherence and a spectrum with non-uniform power distribution. Our work shows that many-body physics creates collective states in driven-dissipative systems, enabling advances in programmable photonics and quantum-optical computing.

physics.optics↗

arXiv2026

A scalable infrastructure for strontium optical clocks with integrated photonics

Optical atomic clocks provide exceptionally accurate and precise signals for timekeeping and precision measurements, but they require high-power, free-space laser configurations that limit scalability. We introduce and explore a scalable infrastructure for strontium (Sr) optical-lattice clocks that incorporates co-design of atomic-beam slowing and a magneto-optical trap (MOT) from an effusion source, generation of complex, three-dimensional free-space laser configurations with a photonic integrated circuit (PIC) and metasurface (MS) optics, and laser stabilization to a frequency-comb supercontinuum generated with integrated nonlinear photonics. With these elements, we realize MOTs of all stable strontium isotopes ($^{84}$Sr, $^{86}$Sr, $^{87}$Sr, $^{88}$Sr) with populations commensurate with natural abundances, demonstrating precise beam control and robustness. Access to laser-cooled alkaline-earth atoms with scalable integrated photonics enables system engineering for optical clocks, quantum sensing, and quantum information, and our experiments demonstrate extensible technologies that advance toward a Sr optical clock largely free of bulk optics.

physics.app-ph↗

arXiv2026

Second-harmonic stabilization of a bulk photonic resonator

The resonant modes of optical cavities provide a powerful resource for laser-frequency stabilization, underpinning high-precision metrology and coherent signal generation. Photonic resonators in which the optical mode propagates through material offer a compact alternative to vacuum Fabry-Perot cavity systems, but their performance is limited by sensitivity of the material to the ambient environment. In this work, we explore second-harmonic (SH) stabilization, which exploits the interplay of a dispersive mode structure against the strict energy conservation of second-harmonic generation. Operationally, we use two, 1550 nm lasers to PDH-detect octave-spaced resonant modes of an ultra-high-Q photonic resonator with one laser frequency-doubled to 775 nm. Under SH stabilization, the microwave frequency offset between the 1550 nm lasers, which we refer to as the SH signal ($f_{SH}$) maps the absolute frequency of the 1550 nm laser to an electronic signal. We characterize this mapping through comparison of the absolute optical frequency inference provided by $f_{SH}$ to an out-of-loop optical measurement, and our results suggest $f_{SH}$ accurately proxies frequency drift. We evaluate the sensitivity and noise floor of this technique, considering contributions from laser locking and bulk material properties, and conclude that $f_{SH}$ is sufficiently sensitive to enhance long-term laser-frequency stability with respect to the resonator. These results demonstrate SH stabilization as a useful technique that infers absolute drift, thereby enabling the increased stability of future compact, precision frequency references.

physics.optics↗

arXiv2025

Monolithic 3D integration of tantalum pentoxide photonics on arbitrary substrates

The photonics landscape encompasses a wide scope of material platforms, each optimized for specific functionalities, yet no platform meets the demands of all current and evolving photonic applications. While combining integrated photonics materials enhances overall capability - such as unifying nonlinear optics, low-loss passive devices, and electro-optics - material and process compatibility remains a major challenge. We introduce full-wafer, monolithic 3D integration of tantalum pentoxide (Ta$_2$O$_5$, hereafter tantala) photonics onto arbitrary substrates, which we explore here with thin-film lithium niobate (LN) on silicon. Tantala's unique properties, importantly room-temperature deposition, low-temperature annealing, and low stress in thick films optimized for phase matching, make it well suited for monolithic 3D integration without compromising substrate performance or compatibility. We demonstrate low-loss, high-quality-factor microresonators and nanophotonics in tantala, robust quasi-phase-matching in poled LN waveguides, and efficient 3D interlayer routing. This enables us to demonstrate a rich palette of nonlinear frequency conversion processes, including $χ^{(3)}$ optical parametric oscillation (OPO) and soliton microcomb generation in tantala microresonators and photonic-crystal resonators, $χ^{(2)}$ second-harmonic generation (SHG) in periodically poled LN, and combinations thereof. Monolithic 3D integration with tantala opens a new paradigm for scalable, multifunctional photonic systems, enabling visible, near-IR, and nonlinear operation into existing photonic infrastructure.

physics.optics↗

arXiv2025

Amorphous metal oxide mixtures for high-Q integrated nonlinear photonics

Choice of material is ubiquitous in integrated photonics to design device properties, whereas changing material composition is much less common. With phase matching as an additional objective, constraints in depositing and patterning thin films limit the use of integrated nonlinear photonics to only select materials. Here, we explore an amorphous metal oxide mixture of titania (TiO2) and tantala (Ta2O5) in which material composition is a tool to enhance and customize photonics properties. In particular, the inclusion of titania reduces the oxygen-defect density in a tantala film, while maintaining a comparable Kerr nonlinear index. With ion-beam sputtering at room temperature, we deposit a thick, ultralow-loss titania-tantala film, and we nanopattern it to create microresonator frequency combs. Titania-tantala microresonators offer lower loss, higher index of refraction, and reduced optical absorption and photorefractive effects. Specifically, the titania-tantala mixture enables microresonator quality factor up to $10^7$ and a direct factor of 1.7 reduction in optical absorption. Our work demonstrates that composition in metal-oxide mixtures is a design parameter alongside the nanofabrication process and photonics design for integrated nonlinear photonics.

physics.optics↗

arXiv2025

Next-generation soliton frequency combs in photonic-crystal and nanocomposite microresonators

Microresonator frequency combs offer tremendous opportunity to advance applications in fundamental research and technology by linking the optical and microwave frequency domains. Kerr-nonlinear microresonators further enable the generation of portable, integrated optical frequency combs, which are called microcombs. However, the dispersion engineering usually suffers from the small, geometric parameter space, and achieving soliton microcombs is challenging and usually requires complicated experimental techniques and setups. In recent years, the invention of photonic-crystal resonators (PhCRs) provides access to solitons in a convenient and stable way while its mechanism has not been fully understood. In this article, we highlight the perspectives of generating solitons for various applications in PhCRs and give a thorough understanding of the dynamics of soliton formation. We also propose a nanocomposite waveguide structure for the optimization of group velocity dispersion (GVD), lifting the limitation on geometric parameter space. We apply it to the design of the pump-harmonic microcomb, a new concept for f-2f self-referencing in microcombs. Inspired by the pulse-driven microresonator, we provide a scheme of two-microresonator network, retaining the convenience of using a continuous wave laser for microcomb generation. Our work depicts a blueprint of achieving the next generation soliton frequency combs in PhCR and nanocomposite microresonators and highlights their great prospects in optical metrology, precision measurement and optical data transmission.

physics.optics↗

arXiv2025

Mixed Precision Photonic Computing with 3D Electronic-Photonic Integrated Circuits

We propose advancing photonic in-memory computing through three-dimensional photonic-electronic integrated circuits using phase-change materials (PCM) and AlGaAs-CMOS technology. These circuits offer high precision (greater than 12 bits), scalability (greater than 1024 by 1024), and massive parallelism (greater than 1 million operations) across the wavelength, spatial, and temporal domains at ultra-low power (less than 1 watt per PetaOPS). Monolithically integrated hybrid PCM-AlGaAs memory resonators handle coarse-precision iterations (greater than 5-bit most significant bit precision) through reversible PCM phase transitions. Electro-optic memristive tuning enables fine-precision updates (greater than 8-bit least significant bit precision), resulting in over 12-bit precision for in-memory computing. The use of low-loss PCM (less than 0.01 dB per cm) and electro-optical tuning yields memristive optical resonators with high Q-factors (greater than 1 million), low insertion loss, and low tuning power. A W by W photonic tensor core composed of PCM-AlGaAs memresonators performs general matrix multiplication (GEMM) across W wavelengths from optical frequency combs, with minimal crosstalk and loss. Hierarchical scaling in the wavelength domain (K) and spatial domain (L) enables this system to address high-dimensional (N) scientific partial differential equation (PDE) problems in a single constant-time operation, compared to the conventional quadratic-time (N squared) computational complexity.

physics.optics↗

arXiv2025

A Kerr soliton Ising machine for combinatorial optimization problems

The growing challenges of scaling digital computing motivate new approaches, especially through the dynamical evolution of physical systems that mimic neural networks and combinatorial optimization problems. While light is a hyper efficient information carrier, intrinsically weak light interactions make direct information processing difficult to implement. Recently, specialized nonlinear photonics have opened new controls over light fields with extraordinary bandwidth, coherence, and the emergence of strong interactions among nonlinear eigenstates like solitons. We harness an ensemble of hundreds of Kerr-nonlinear microresonator solitons and implement an analog feedback network to create an Ising machine with fully programmable all-to-all interactions. By increasing the feedback for self, on-diagonal interactions, each soliton exhibits a universal spin-like bifurcation. Using this palette of interactions amongst the entire soliton ensemble, we encode the Ising machine to solve the benchmark Boolean satisfiability problem (SAT). The combination of uniform soliton interactions and the compatibility of our Ising machine with high-speed data interconnects enables rapid and precise solutions of complex SAT problems. Indeed, the soliton properties bound the tradeoff of optical power and time use by the machine at approximately 10 mW and 1 $μ$s for a single feedback step. We performed >10,000 trials on more than 100 randomly generated SAT instances to evaluate the Ising machine, demonstrating the potential to exceed the performance of benchmark digital SAT solvers. Our work highlights the convergence of optical nonlinearity, ultralow loss photonics, and optoelectronic circuits, which can be combined for a wide range of computation-acceleration tasks.

physics.optics↗

arXiv2025

Universal electronic synthesis by microresonator-soliton photomixing

Access to electrical signals across the millimeter-wave (mmW) and terahertz (THz) bands offers breakthroughs for high-performance applications. Despite generations of revolutionary development, integrated electronics are challenging to operate beyond 100 GHz. Therefore, new technologies that generate wideband and tunable electronic signals would advance wireless communication, high-resolution imaging and scanning, spectroscopy, and network formation. Photonic approaches have been demonstrated for electronic signal generation, but at the cost of increased size and power consumption. Here, we describe a chip-scale, universal mmW frequency synthesizer, which uses integrated nonlinear photonics and high-speed photodetection to exploit the nearly limitless bandwidth of light. We use a photonic-integrated circuit to generate dual, microresonator-soliton frequency combs whose interferogram is fundamentally composed of harmonic signals spanning the mmW and THz bands. By phase coherence of the dual comb, we precisely stabilize and synthesize the interferogram to generate any output frequency from DC to >1000 GHz. Across this entire range, the synthesizer exhibits exceptional absolute fractional frequency accuracy and precision, characterized by an Allan deviation of 3*10^(-12) in 1 s measurements. We use a modified uni-traveling-carrier (MUTC) photodiode with an operating frequency range to 500 GHz to convert the interferogram to an electrical signal, generating continuously tunable tones across the entire mmW band. The synthesizer phase noise at a reference frequency of 150 GHz is -83 dBc/Hz at 100 kHz offset, which exceeds the intrinsic performance of state-of-the-art CMOS electronics. Our work harnesses the coherence, bandwidth, and integration of photonics to universally extend the frequency range of current, advanced-node CMOS microwave electronics to the mmW and THz bands.

physics.optics↗

arXiv2025

Activating high-power parametric oscillation in photonic-crystal resonators

By engineering the mode spectrum of a Kerr microresonator, we selectively activate nonlinear phase matching amongst broadband parametric gain. At threshold, optical parametric oscillators (OPOs) emerge from vacuum fluctuations in the presence of a pump laser, and above threshold, OPOs seed the formation of intraresonator patterns and states, such as chaos and solitons. These competing nonlinear processes hinder an important application of OPOs as wavelength-variable, low-noise sources. Recently, nanopatterned microresonator OPOs have leveraged photonic crystal bandgaps to enable universal phase matching and control of nonlinear interactions. Here, we explore a design paradigm optimized for high-output power that uses geometric dispersion to suppress nonlinear interactions and a photonic crystal bandgap to activate only a single OPO interaction. Our devices convert an input pump laser to output signal and idler waves with powers exceeding 40 mW while maintaining spectral purity and side-mode suppression ratios greater than 40 dB. We show that this approach suits custom wavelengths by measuring four independent oscillators that vary only photonic crystal parameters to select output waves. Our experiments demonstrate that microresonators functionalized by photonic crystals offer a versatile and lossless palette of controls for nonlinear laser conversion.

physics.optics↗

arXiv2025

Implementing photonic-crystal resonator frequency combs in a photonics foundry

We explore an AIM Photonics silicon-nitride platform to fabricate photonic-crystal resonators for generating optical parametric oscillators (OPO) and soliton microcombs. Our approach leverages the scalability and fine feature size of silicon-nitride processing on large-scale silicon wafers to achieve low-loss, high-Q microresonators, functionalized by nano-scale photonic-crystal structures. We demonstrate intrinsic microresonator quality factor up to 1.2*10^7 with complete foundry fabrication on 300 mm silicon, a 700 nm thick silicon-nitride device layer, and inclusion of complex nanophotonics. These features enable a host of nonlinear nanophotonics sources on the platform, including OPOs, microcombs, parametric amplifiers, squeezed-light generators, and single-photon sources. By fine-tuning the photonic-crystal design parameters, we achieve broad tunability in the frequency of the OPO output, spanning a significant portion of the near-infrared. Additionally, we observe the formation of soliton frequency combs, enabled by the precise dispersion engineering of the microresonators. These results highlight the potential of widely accessible, photolithographically patterned, silicon-nitride photonics to enable wide access to and complex integration of frequency-comb sources, with applications in spectroscopy, metrology, and communications.

physics.optics↗

arXiv2025

Heterogeneous tantala photonic integrated circuits for sub-micron wavelength applications

Atomic and trapped-ion systems are the backbone of a new generation of quantum-based positioning, navigation, and timing (PNT) technologies. The miniaturization of such quantum systems offers tremendous technological advantages, especially the reduction of system size, weight, and power consumption. Yet, this has been limited by the absence of compact, standalone photonic integrated circuits (PICs) at the wavelengths suitable for these instruments. Mobilizing such photonic systems requires development of fully integrated, on-chip, active components at sub-micrometer wavelengths. We demonstrate heterogeneous photonic integrated circuits operating at 980 nm based on wafer-scale bonding of InGaAs quantum well active regions to tantalum pentoxide passive components. This high-yield process provides > 95 % surface area yield and enables integration of > 1300 active components on a 76.2 mm (3 inch) silicon wafer. We present a diverse set of functions, including semiconductor optical amplifiers, Fabry-Perot lasers, and distributed feedback lasers with 43 dB side-mode suppression ratio and > 250 GHz single-mode tuning range. We test the precise wavelength control and system level functionality of the on-chip lasers by pumping optical parametric oscillation processes in microring resonators fabricated on the same platform, generating short-wavelength signals at 778 nm and 752 nm. These results provide a pathway to realize fully functional integrated photonic engines for operation of compact quantum sensors based on atomic and trapped-ion systems.

physics.optics↗