arXiv subjects

Kartik Srinivasan

Publications and source records attributed to Kartik Srinivasan.

At least 19 recordsLinked to original sources

arXiv2026

Bridging high-Q and Kerr-nonlinear photonics using modal phase matching

Integrated Kerr microresonators provide on-chip optical nonlinearity for wavelength conversion, optical frequency combs, and quantum light sources. Traditionally, their dispersion engineering has tied nonlinear functionality to resonator geometry, forcing trade-offs with other device objectives. In particular, Kerr microresonators usually feature narrow resonator waveguides, but wide waveguides support higher Q through reduced sidewall scattering. We propose that modal phase matching - invoking multiple spatial mode families to satisfy dispersion requirements - facilitates Kerr nonlinear optics beyond traditional geometries. Working with a commercial foundry, we design and fabricate high-$ (>10^7) microresonators on a 160-nm-thick silicon nitride platform and demonstrate Kerr optical parametric oscillation. We achieve 20% conversion efficiency and gap-free wavelength tuning over >1 nm for parametric oscillation at the cesium D1 transition. Modal phase matching further supports pumping in both 1060-nm and 795-nm bands, without custom device layers, for wavelength generation between 600 nm to 1400 nm. Our work expands the Kerr design space, effectively decoupling Q and dispersion to create new opportunities with high-Q nonlinear devices.

physics.optics↗

arXiv2026

Single-Shot Realization of 10000-Mode Octave-Spanning Artificial Gauge Fields

Artificial gauge fields (AGFs) enable photons and other bosons to emulate fermionic phenomena such as chiral edge transport and quantum Hall phases; however, existing theories and realizations remain confined to narrow bandwidths under single-mode approximation. We introduce a general theoretical framework for ultra-broadband, multi-modal dispersion-corrected AGFs in both linear and nonlinear regimes. Using integrated photonics, we realize over 100 distinct AGFs hosting more than 10,000 modes across nearly an optical octave -- the first frequency-comb realization of the integer quantum Hall model for photons. Leveraging Kerr nonlinearity, we achieve single-shot AGF control beyond waveguide dispersion, robust to wafer-scale fabrication variations. Our results establish a new regime of ultra-broadband multimodal AGFs, opening pathways to exotic dispersion-corrected AGF dynamics and simulations, as well as volume-manufacturable device functionalities such as waveguide-dispersion-resilient photonic circuits, and AGF-enabled programmable nonlinear and quantum optics and optoelectrics.

physics.optics↗

arXiv2026

Photogalvanic second harmonic generation in Si3N4 for 1 Hz level on-chip metrology and spectroscopy

The coherent photogalvanic (PG) effect induces an effective $χ^{(2)}$ nonlinearity in natively $χ^{(3)}$ silicon nitride integrated photonics, unlocking pathways toward chip-scale precision spectroscopy and optical clockworks via second harmonic generation (SHG). While quasi-phase-matched PG-SHG using spatially varying internal electric fields offers tuning flexibility, it is often accompanied by pump-power- and detuning-dependent frequency offsets. Here, we investigate whether direct phase-matching---utilizing an intermodal scheme that generates a spatially uniform electric field---can support metrologically compatible SHG. By comparing the fundamental and doubled optical frequencies in a silicon nitride microresonator, we test the preservation of the (2:1) frequency ratio in directly phase-matched PG-SHG. We observe a frequency offset of $< 1\mathrm{~Hz}$, contrasting with previous limitations in quasi-phase-matched configurations. Furthermore, we measure a residual fractional frequency instability of $2\times 10^{-15}$ at $1\mathrm{~s}$, averaging down to the $10^{-16}$ level at $1000\mathrm{~s}$, with multi-hour deviations remaining below $1\mathrm{~Hz}$. These results establish directly phase-matched PG-SHG as a robust, metrologically compatible route to effective $χ^{(2)}$ functionality, combining sub-Hz frequency-ratio fidelity and high coherence on a mature integrated platform for optical clockworks, self-referencing, and precision spectroscopy.

physics.optics↗

arXiv2026

Fock-state preparation based on amplitude amplification in cavity QED

In this work, we develop a coherent control technique for cavity QED based on amplitude amplification. We consider two physical platforms. In the first setting, we study a three-level quantum emitter coupled to a single mode of an optical cavity and introduce a protocol for producing traveling single photons based on oblivious amplitude amplification. As the key ingredient of our protocol, we propose an extension of oblivious amplitude amplification which uses reflection unitaries solely on the signal qubit, along with $U$ and $U^\dagger$, where the unitary $U$ prepares the initial state. Our approach improves the scaling of the single-photon-generation protocol length from $N\sim 1/p$ to $N\sim 1/\sqrt{p}$, with $p$ denoting the success probability of obtaining a short single photon from a single application of the weak control pulse. Furthermore, our protocol also reduces the error from intrinsic cavity loss compared to protocols using a single strong control pulse in various experimentally relevant regimes, suggesting the application of our methods for error reduction. In the second setting, we consider a superconducting qubit coupled to a single bosonic mode of a microwave cavity in a circuit QED architecture in the dispersive regime for preparing Fock states. Using fixed-point amplitude amplification, we obtain a protocol for preparing Fock states whose length scales as $O(n^{1/4})$, where $n$ is the number of photons. Additionally, as an application of our methods for state preparation, we describe a protocol for preparing NOON states.

quant-ph↗

arXiv2026

All-optical Synchronization of Breather Solitons in a Kerr Microresonator

Microresonator Kerr solitons are promising candidates for the realization of miniaturized on-chip optical frequency combs. For specific system parameters, these solitons are associated with oscillatory instabilities, leading to breathing dynamics characterized by periodically modulated temporal and spectral profiles. In this regime, the solitons form a frequency comb comprised of primary comb lines surrounded by sidebands separated by the breathing frequency. Here, we numerically and experimentally demonstrate that the breathing sidebands can be all-optically synchronized to a weak monochromatic laser injected into the cavity, thus providing direct control of the soliton oscillation frequency. We judiciously characterize the synchronization process, and show that it is accompanied by a strong reduction of noise in the soliton's breathing. Our results provide fundamental insights on oscillatory dissipative structures, and could enable new forms of composite optical frequency combs.

physics.optics↗

arXiv2026

Automated Vector-Scanning Spectroscopy for Large-Scale Characterization of Single Quantum Emitters

The inherent spatial randomness and broad spectral heterogeneity of epitaxial quantum dots (QDs) -- one of the most mature classes of solid-state quantum emitters -- remains a major obstacle to their scalable deployment in integrated photonic quantum technologies. Overcoming this challenge requires deterministic fabrication strategies capable of precisely aligning nanophotonic structures with high-quality emitters, which in turn demands efficient and automated single-QD characterization. Despite substantial progress in optical measurement techniques, a platform capable of autonomous, data-efficient, and sufficiently versatile characterization of single quantum dots at the chip scale remains lacking. Here, we introduce an automated cryogenic measurement platform that combines wide-field photoluminescence imaging with vector-stage-scanning confocal spectroscopy to enable high-throughput, chip-scale targeted optical characterization of individual QDs. Using this platform, we automatically acquire photoluminescence data from thousands of GaAs/AlGaAs QDs on a single chip. We demonstrate how this extensive dataset enables identification of high-performance emitters for future deterministic device fabrication, while simultaneously revealing statistical trends across the QD ensemble. By uniting data-efficient targeted measurements with scalable automation, our platform establishes a foundation for large-scale quantum photonic integration and the high throughput characterization framework needed to accelerate materials optimization.

physics.optics↗

arXiv2026

Broadband Chromatic Dispersion of Thermo-refractive Coefficients and its Impact in Silicon Nitride Nonlinear Photonics

The thermo-refractive effect is a cornerstone of frequency and phase tuning in photonic integrated circuits. In particular, it enables control of phase-matching for integrated nonlinear processes. Chromatic dispersion of the group and effective refractive indices and modal confinement are standard considerations in design, but material thermo-refractive coefficients (TRCs) are typically taken to be fixed for the guiding and cladding materials. Here, we demonstrate that the assumption of non-dispersive TRCs across an octave of bandwidth between the telecom and visible results in a significant discrepancy between measured and simulated resonance frequencies of an integrated Si3N4/SiO2 microring resonator. We uncover a 7 % variation in Si3N4 and SiO2 material TRCs across this range, finding that the variation of dneff /dT from material TRCs is 1.3 times that from modal confinement. This accurately matches a temperature-dependent Lorentz oscillator model describing their chromatic dispersion. By integrating these dispersive TRCs into a multi-physics finite-element model, we achieve precise correspondence with experimentally measured temperature-dependent resonance frequency shifts across the octave, including in the context of second harmonic generation devices. Our results provide a physical framework and a universal predictive workflow for the design of high-efficiency, multi-wavelength nonlinear optical processes, fundamentally improving the thermal control of integrated photonic devices.

physics.optics↗

arXiv2026

Thermally accessible broadband soliton microcombs in silicon carbide enabled by dynamic polarization control

Optical microcombs generated in high-Q microresonators are promising chip-scale light sources for applications ranging from optical communications to spectroscopy and metrology. However, thermo-optic instabilities remain a major obstacle to reliable soliton access. Self-cooling using auxiliary modes can stabilize the intracavity power, yet part of the power is continuously allocated to thermal compensation rather than comb generation, thereby limiting comb power and bandwidth. Here we propose a thermal compensation scheme based on dynamic polarization control. During soliton initiation, a fraction of the pump is coupled to an orthogonally polarized mode to provide self-cooling and ensure reliable soliton access. After soliton formation, polarization rotation and pump tuning transfer this cooling power to the comb-generating mode, enabling efficient single-soliton operation. Using this approach, we experimentally demonstrate a broadband 108-GHz-FSR single-soliton microcomb spanning over 450 nm, together with approximately 39% improvement in the 20-dB bandwidth and 60% increase in comb power relative to the static self-cooling configuration. This dynamic polarization-based thermal compensation enables efficient use of available laser power and provides a practical route to high-performance soliton microcombs in platforms with strong thermo-optic effects.

physics.optics↗

arXiv2026

Self-aligned optical microcomb emerging between octave separated lasers

Optical frequency combs (OFCs) are frequency rulers essential for precision metrology, next generation navigation, and testing of fundamental physics. Despite intense efforts, chip-integrated OFCs remain laboratory-bound, unable to fulfill their promise of compact and cost-effective deployment. While improvement in fabrication and integration are important, a conceptual limitation has fundamentally stymied progress: on-chip OFC architectures have aimed to miniaturize their table-top counterparts and relied on cascading outward from (i.e., spectrally broadening) a single pump. In integrated platforms, this approach does not readily allow for the generation of strong and low-noise octave-spaced signals that are crucially needed for robust zero-frequency offset detection. Here, we overcome this limitation via an architectural inversion where an optical microcomb forms by filling the spectrum between two octave-separated pump lasers. The two pumps generate a parametrically driven cavity soliton (PDCS) in an integrated $χ^{(3)}$ resonator, which robustly self-aligns to (i.e., synchronizes with) the pump lasers across multiple foundry-fabricated devices and operating configurations. This produces a single octave-spanning comb extending from telecom to visible wavelengths, whose zero-frequency offset is completely defined by the two harmonically-related pump lasers, and can therefore be reliably detected and stabilized. We showcase our platform's capabilities by executing all of the three core tasks of OFC metrology: optical frequency synthesis, low-noise millimeter-wave generation, and integrated optical clock readout, using the same self-aligned microcomb with only its input locks changed.

physics.optics↗

arXiv2026

Universal Bright-Bright Integrated Soliton Molecule via Parametric Binding

Dissipative Kerr solitons (DKSs) have emerged as the preferred solution for on-chip integrated optical frequency comb (OFC) generation in metrology. A multi-pumped DKS enables either all-optical trapping in the Kerr-induced synchronization regime, or a multi-component OFC with \greg{a locked repetition rate yet with constant frequency offsets between the components} in the multi-color DKS regime. The multi-color DKS regime is of particular interest since nonlinear mixing between the DKS and the secondary pumped component generates idler waves at different frequencies that are useful for spectral extension of the DKS comb. Here, we explore multi-color idler generation at frequencies in which the resonator free spectral range matches that at the DKS. We demonstrate theoretically and experimentally that without phase matching, the idler forms a bright pulse fundamentally bound to the bright DKS through parametric interaction, despite occurring in normal dispersion. Our work can enable new applications in metrology and spectroscopy of quantum systems toward visible wavelengths, as the parametric nature of our bright-bright state eliminates dependence on dispersion regime or visible wavelength pumping.

physics.optics↗

arXiv2026

Dissipative Kerr Soliton Self-Balancing from Kerr-Induced Synchronization

Integrated frequency comb sources are a key enabling technology for frequency metrology applications. Their on-chip integration promises to bring metrology capacity outside of the lab, particularly since they can operate at low continuous-wave pump laser power in the dissipative Kerr soliton (DKS) regime. Yet, such small foot-print and low power comes at a cost: higher noise and overall lower comb power. In particular, this translates to highly challenging detection and locking of the carrier-envelope offset, necessary for complete stabilization of the comb. Recently, Kerr-induced synchronization (KIS) of a DKS to a reference laser has been demonstrated as a tool for passive all-optical stabilization of DKS microcombs, with fundamental modification to the DKS and microcomb properties. Here, we demonstrate that the combination of additional power from the reference laser (now part of the DKS) and the KIS phase locking that pins the repetition rate together fundamentally alter the DKS, forcing an energy redistribution to maintain its center of mass. We demonstrate this self-balancing effect theoretically, which in a pure quadratic dispersion resonator leads to reference-dependent recoil. With higher-order dispersion through which the DKS yields phase-matched dispersive waves (DWs), we demonstrate that self-balancing increases the DW radiation, experimentally showing a 22 dB increase of comb teeth at 780 nm in an octave-spanning microcomb for efficient deployable carrier-envelope offset detection.

physics.optics↗

arXiv2026

Microring Resonator Dispersion Metrology with Neural Networks

Precise knowledge of resonator dispersion, from both geometric and material contributions, is essential for reliable high-performance nonlinear integrated photonics devices, such as optical parametric oscillators, frequency doublers, and integrated optical frequency combs. However, direct measurements at the fabrication level provide limited knowledge, whether through destructive cross-section imaging or non-destructive ellipsometry, while complete optical characterization that enables precise dispersion metrology is time-consuming and poorly suited for mass-scale foundry fabrication. In this work, we develop a machine learning framework to solve three complementary problems: (i) predicting resonator geometric dimensions, (ii) identifying the correct material dispersion, and last, but not least, (iii) precisely reconstructing the integrated dispersion spectrum directly from ring dimensions. These three neural networks together enable both inverse and forward characterization of microring resonators. Using numerically generated datasets based on Sellmeier-type material models, we demonstrate <1 nm ring dimension prediction accuracy without noise, <8 nm prediction accuracy with ~45 dispersion samples under a realistic frequency measurement noise level (50 MHz), and ~16 nm prediction accuracy at a higher noise level (200 MHz). The Sellmeier model classification exceeds 99% accuracy in all cases. Importantly, dispersion sampled far from the pump resonances proves most informative, reducing full-spectrum characterization requirements. The forward-prediction network reconstructs dispersion spectra from the ring dimensions with high accuracy. Our results highlight the potential of machine learning applied to dispersion data as a rapid, non-destructive tool for wafer-scale quality control and process monitoring in photonic foundries.

physics.optics↗

arXiv2025

Enabling atom-clad waveguide operation in a microfabricated alkali vapor-photonic integrated circuit

Integrating alkali atomic vapors with nanophotonic devices offers a scalable route to quantum technologies that leverage strong atom-photon interactions. While there have been many approaches to such integration, the general reliance on traditional glass vapor cells, distilled alkali metals, and epoxy sealing limits reproducibility and scalability. Moreover, mitigating adverse Rb-photonics interactions is essential, particularly as devices become more compact and the alkali source lies in close proximity to the photonic elements. Here, we demonstrate the successful operation of compact and fully integrated devices that combine silicon nitride photonic integrated circuits (PICs) with microfabricated borosilicate vapor cells and pill-type rubidium (Rb) dispensers through hermetic seals via anodic bonding. We show how successful operation hinges on optically activating the dispenser in a low-power pulsed mode, releasing controlled amounts of Rb vapor on demand while mitigating photonic degradation. Simultaneously, a counter-propagating desorption laser completely suppresses Rb-induced losses and enables waveguide-based atomic vapor spectroscopy. Using this approach, we demonstrate repeatable control of vapor density by tuning activation pulse length, duty cycle, and device temperature. These results establish a compact, manufacturable, and scalable vapor-PIC device, and set the stage for future demonstrations in cavity quantum electrodynamics, quantum nonlinear optics, and chip-scale atomic sensors.

physics.optics↗

arXiv2025

Quantum Metamorphosis: Programmable Emergence and the Breakdown of Bulk-Edge Dichotomy in Multiscale Systems

Multiscale synergy -- the interplay of a system's distinct characteristic length, time, and energy scales -- is becoming a unifying thread across many contemporary branches of science. Ranging from moiré and super-moiré materials and cold atoms to DNA-templated superlattices and nested photonic networks, multiscale synergy produces behaviors not obtainable at any single scale alone. Yet a general framework that programs cross-scale interplay to steer spectra, transport, and topology has been missing. Here, we elevate multiscale synergy from a byproduct to a general design principle for emergent phenomena. Specifically, we introduce a scale-programmable framework for hierarchically nested lattices (HNLs) that can host quantum metamorphosis (QuMorph) -- a continuous evolution between system-dependent features governed by a dimensionless tunable parameter $α$ (the relative hopping). To exemplify, we show an HNL, in which as $α$ changes, the spectrum metamorphoses from integer quantum Hall-like to anomalous quantum Hall-like, passing through a cocoon regime with proliferating mini-gaps. This multiscale mixing yields multiple novel phenomena, including hybrid edge-bulk states, scale-dependent topology, topologically embedded flat bands, and isolated edge bands. We propose a feasible photonic implementation using commercially available coupled-resonator arrays, outline spatial-spectral signatures to map QuMorph, and explore applications for multi-timescale nonlinear optics. Our work establishes a scalable and programmable paradigm for engineering multiscale emergent phenomena.

physics.optics↗

arXiv2025

A vapor-cavity-QED system for quantum computation and communication

In this work, we propose performing key operations in quantum computation and communication using room-temperature atoms moving across a grid of high-quality-factor, small-mode-volume cavities. These cavities enable high-cooperativity interactions with single atoms to be achieved with a characteristic timescale much shorter than the atomic transit time, allowing multiple coherent operations to take place. We study scenarios where we can drive a Raman transition to generate photons with specific temporal shapes and to absorb, and hence detect, single photons. The strong atom-cavity interaction can also be used to implement the atom-photon controlled-phase gate, which can then be used to construct photon-photon gates, create photonic cluster states, and perform non-demolition detection of single photons. We provide numerics validating our methods and discuss the implications of our results for several applications.

quant-ph↗

arXiv2025

Toward Chaotic Group Velocity Hopping of an On-Chip Dissipative Kerr Soliton

Chaos enables randomness-based applications, particularly in photonic systems. Integrated optical frequency combs (microcombs) have previously been observed in either chaotic modulation instability or stable, low-noise dissipative Kerr soliton (DKS) regimes. In this work, we demonstrate a new microcomb state where a single DKS exhibits chaotic behavior. By phase modulating the Kerr-induced synchronization (KIS) between a DKS and an externally injected reference laser, we observe chaotic group velocity hopping of the soliton, causing random transitions of the repetition rate. Using a chip-integrated octave-spanning microcomb, we experimentally validate the second-order Adler equation describing KIS, allowing us to predict and demonstrate this chaotic DKS hopping. This work connects nonlinear dynamics with optical soliton physics, providing a deterministic framework for triggering microcomb chaos in the solitonic state.

physics.optics↗

arXiv2025

Integrated broadband optical isolator via dynamic rotating destructive interference

Photonic integrated circuits route and shape light on a chip, but back-reflections feed back into coherent on-chip lasers, destabilizing operation and corrupting signals. Robust operation requires an integrated optical isolator that strongly suppresses backward propagation while maintaining low-loss, broadband forward transmission. However, prior on-chip isolators rely on magneto-optic materials or resonance-based filters, which respectively demand non-standard processes or inherently constrain bandwidth. Here, we propose and experimentally demonstrate a traveling-wave optical isolator without magnetic materials or resonant elements. By driving four parallel optical channels with periodic RF waves, we realize dynamic rotating destructive interference that continuously cancels backward-propagating light while leaving forward-propagating light unaffected. We achieve about 30 dB isolation at a wavelength of 789.7 nm and maintain over 24 dB isolation across an approximately 30 nm bandwidth (770 nm to 800 nm), including >20 dB isolation for two simultaneous lasers within an approximately 10 nm wavelength window. This wavelength span covers key alkali atomic transitions, enabling strong suppression of feedback-induced frequency noise and laser instability in atomic spectroscopy, laser cooling, and locking applications. We demonstrate a practical, broadband on-chip isolator applicable from the visible to the near-infrared, which is a crucial step toward fully integrated photonic platforms.

physics.optics↗

arXiv2025

On-chip multi-timescale spatiotemporal optical synchronization

Mode-locking mechanisms are key resources in nonlinear optical phenomena, such as micro-ring solitonic states, and have transformed metrology, precision spectroscopy, and optical communication. However, despite significant efforts, mode-locking has not been demonstrated in the independently tunable multi-timescale regime. Here, we vastly expand the nonlinear mode-locking toolbox into multi-timescale synchronization on a chip. We use topological photonics to engineer a 2D lattice of hundreds of coupled silicon nitride ring resonators capable of hosting nested mode-locked states with a fast (near 1 THz) single-ring and a slow (near 3 GHz) topological super-ring timescales. We demonstrate signatures of multi-timescale mode-locking including quadratic distribution of the pump noise with the two-time azimuthal mode dimensions, as expected by mode-locking theory. Our observations are further corroborated by direct signatures of the near-transform-limit repetition beats and the formation of the temporal pattern on the slow timescale. Moreover, we show that these exotic properties of edge-confined mode-locked states are in sharp contrast to bulk and single-ring counterparts and establish a clear pathway for their identification. Our unprecedented demonstration of mode-locking in topological combs unlocks the implementation of lattice-scale synchronization and independently tunable multi-timescale mode-locking phenomena, also the exploration of the fundamental nonlinearity-topology interplay on a chip.

physics.optics↗