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Physics Physics Optics

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Monday 24 August

Optics · Cross-listed from cs.MA

First Demonstration of Multi-Agent LLM System for Million-Scale Optical Link Management in Global Production AIDCs

Jingyi Su, Yihao Zhang, Dianxuan Fu et al. (+15 more)

We present the first LLM-powered multi-agent system for autonomous fault management across millions of optical links in production AIDCs. Refined via SFT and continuous memory evolution, it achieves 97.7% F1 and over 60% fault-incident reduction, outperforming SOTA LLMs on a ten-week field data evaluation.
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All authors Jingyi Su, Yihao Zhang, Dianxuan Fu, Leiyan Fei, Juan Wang, Mengfan Dai, Qing Liu, Xiong Wu, Yufeng Jiang, Cheng Chen, Bowen Zhang, Peilong Wang, Xi Chen, Zonglong He, Hongchen Yu, Zhicheng Ye, Weisheng Hu, Qunbi Zhuge

Optics

Extreme Ultrafast Dynamics of the Refractive Index in Transparent Conductive Oxides: Theory and Experiment

Noa Konforty, Graham G. Brown, Ohad Segal et al. (+5 more)

Recent experiments in transparent conductive oxides (TCOs) have revealed light-induced order-unity variations in the refractive index occurring at extreme time scales, as short as a few-femtoseconds. These experimental observations remain unexplained, especially the ultrafast 10-20 femtoseconds relaxation of the index change, that cannot be explained by known phonon-mediated relaxation processes. Here, we present a simplified model followed by comprehensive simulations describing the phenomena, relying on the microscopic dynamics of electrons in TCOs under powerful ultrafast laser pulses. With this physical model, we predict and experimentally observe the unexplored regime of intraband modulation of electrons in the conduction band, leading to ultrafast oscillations of the refractive index. The observation of the oscillations validates the theory as a predictive tool, utilizing it to design experiments targeting novel effects that hinge on extreme alterations of optical properties of materials, such as photonic time-crystals and a plethora of novel extreme ultrafast phenomena.
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All authors Noa Konforty, Graham G. Brown, Ohad Segal, Oded Schiller, Yonatan Plotnik, Vladimir M. Shalaev, Misha Ivanov, Mordechai Segev

Optics

Photonic Crystal Defect Nanocavities Based on Monocrystalline Yttrium Iron Garnet

Kota Taniguchi, Siyuan Gao, Tatsuya Kitai et al. (+5 more)

Monocrystalline yttrium iron garnet (YIG) is a key material for magneto optics and quantum magnonics owing to its high optical transparency, large magneto-optical (MO) effects at room temperature, and exceptionally-long spin coherence. While rich MO phenomena have been demonstrated in the microwave regime, extending these concepts to technologically important telecommunication wavelengths remains challenging due to the difficulty of fabricating high-quality YIG nanostructures. Here, we demonstrate photonic crystal (PhC) defect nanocavities based on monocrystalline Bi-substitudted YIG by developing a YIG-on-insulator platform and high-precision YIG nanopatterning. The fabricated nanocavities exhibit cavity resonances around lambda = 1500 nm with Q factors up to 1,800 and a mode volume V of 1.1(lambda/n)^3, corresponding to Q/V reaching around 10^3. The measured Q factor is primarily governed by intentionally introduced lattice modulations for out-of-plane light coupling, suggesting that further optimization of the cavity geometry and measurement configuration could yield an order-of-magnitude improvement of the experimental Q factor. YIG-based PhC nanocavities provide a platform for strongly confined light-magnetism interactions in the optical regime, opening pathways toward downsized nonreciprocal photonic devices and enhanced photon-magnon coupling.
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All authors Kota Taniguchi, Siyuan Gao, Tatsuya Kitai, Takeru Yambe, Daisuke Sato, Hironobu Yoshimi, Satoshi Iwamoto, Yasutomo Ota

Optics

Sensitivity Limits for $\phi$-OTDR

Juan M. Marin, Roman Ermakov, Huwei Wang et al. (+2 more)

We demonstrate a new lower bound on the sensitivity of $\phi$-OTDR by estimating phase using Kalman filtering. Numerical analysis shows a $\sim$35-dB reduction in the minimum detectable SNR, compared to when using conventional phase estimation.
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All authors Juan M. Marin, Roman Ermakov, Huwei Wang, Francesco Da Ros, Darko Zibar

Optics

Self-consistent modelling of all-optical switching and magneto-optic readout in an integrated Si$_3$N$_4$/GdFeCo waveguide

Muhammad Arief Mulyana, Budi Adiperdana and Ayi Bahtiar

What a guided beam carries after passing through an all-optically switched magnetic film has not been computed, although such switching has been demonstrated on a silicon nitride waveguide with electrical readout. We close the chain for an integrated Si$_3$N$_4$/GdFeCo element, an 8 nm film on a 60 $\mu$m waveguide, coupling a three-dimensional dispersive finite-difference time-domain solver to absorbed optical work, a four-temperature model, and stochastic two-sublattice Landau-Lifshitz-Bloch dynamics with a fluctuation-dissipation-consistent Langevin field, the magnetization feeding back into the gyrotropic permittivity that a second guided shot reads. Transmission, reflection and absorption are magnetization-blind, closing to 0.974-0.975 and shifting by at most 0.02 between saturated, demagnetized and multidomain films, because magnetization enters the dielectric tensor only through an antisymmetric element on which absorbed power depends at second order; the odd-in-magnetization polarimetry separates them by an order of magnitude in Faraday rotation and two in Kerr. The guided geometry levies a cost free-space measurement does not: a $-11.77^\circ$ geometric pedestal on the reflected channel, exceeding the $8.24^\circ$ rotation it hides. Referencing against a demagnetized film returns it to $0.063^\circ$. The transmitted mode carries a second signature in its lobe balance, needing no polarimetry. Calibrated pulses toggle 0.859 of the film from either saturated state across a $2.4\times$ fluence window, and the shortfall from unity is photonic rather than magnetic: the switched fraction is the complementary cumulative distribution of the guided-mode absorption map at the single-cell threshold, holding to $8\times10^{-4}$ at five full-wave anchors. From exactly zero magnetization, branch selection passes to the Langevin field alone, at occupancy $0.502 \pm 0.004$ over 16 seeds.
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Optics

Geometry-calibrated equilibrium sensing for inverse design of nonlocal topological photonic lattices

Fatemeh Davoodi and Jeffrey McCord

Topological photonic lattices are commonly designed using short-range Hamiltonians, yet realistic nanophotonic structures are governed by geometry- and wavelength-dependent long-range electromagnetic interactions. Here we introduce a geometry-calibrated quantum equilibrium-propagation framework for inference and inverse design in finite nonlocal plasmonic Su-Schrieffer-Heeger lattices. A two-qubit equilibrium sensor is trained in effective-coupling space to distinguish boundary-localized from trivial finite-lattice responses. Because labels inherited from the nearest-neighbor SSH model become unreliable in the presence of nonlocal hopping, each sample is independently relabeled using nonlocal winding numbers and a finite-gap criterion. On this physics-verified evaluation set, the sensor achieves 99.8% sensitivity and 98.1% specificity. A physics-gated robustness score then ranks verified configurations by boundary response, response contrast, gap stability and compatibility with the selected nonlocality regime. Full-wave extinction spectra of isolated and paired gold nanoparticles establish a geometry-to-coupling calibration linking particle size and separation to wavelength-resolved pair couplings. Projecting this calibration onto the verified coupling landscape identifies a finite plasmonic geometry supporting spectrally distinct corner- and edge-dominated responses at 546 and 642 nm, with sector-to-bulk intensity contrasts of $2.4 \times 10^{4}$ and $1.5 \times 10^{3}$, respectively. The framework links realistic electromagnetic geometry to nonlocal topological design, moving beyond nearest-neighbor design rules with physics-verified, geometry-resolved inference.
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Optics

Topological space-time waves in complex channels

Renwei Zou, Kelsey Everts, Andrew Forbes et al. (+1 more)

Structured light in space and time has become a powerful playground in which to explore the fundamental physics of wave systems, while simultaneously introducing new exotic forms of light, from spatio-temporal vortices to toroidal pulses of light. Yet their creation remains restricted by complex optical systems while directly observing their evolution in arbitrary channels remains elusive, complicated by the interplay of dispersion and diffraction and exacerbated by the lack of suitable detection tools. Here we create topological space-time beams in a single step by a resonant response of a symmetry-broken metasurface, mixing spatial, temporal and polarisation degrees of freedom in a single microwave field. Our realisation in the microwave regime allows us to directly observe their dynamics in arbitrary channels, from free-space to complex random media, showing the preservation of topology while the foundational degrees of freedom are scrambled. We use our control to show how to unscramble the space-time properties for the first crosstalk-free transmission of space-time waves. Our work advances the physics of space-time waves, introduces a new toolkit for their creation and control, and offers an exciting roadmap to their exploitation in real-world scenarios, e.g., for robust communications through noisy channels.
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All authors Renwei Zou, Kelsey Everts, Andrew Forbes, Yungui Ma

Optics

A swept-source dual-comb spectrometer on a chip

Johannes Fuchsberger, Theodore P. Letsou, Paul Chevalier et al. (+4 more)

Dual-comb spectroscopy (DCS) enables high-speed, high-resolution spectroscopy by down-converting optical spectra to the radio-frequency (RF) domain through the interference of two mutually detuned frequency combs. Accurately resolving narrow molecular absorption features requires closely spaced comb lines generated by large laser cavities with long round-trip times, thereby hindering the miniaturization of high-resolution spectrometers. Here, we circumvent this limitation by demonstrating a swept-source dual-comb spectrometer using two unidirectional racetrack semiconductor lasers integrated on the same chip. The traveling-wave frequency combs are generated by strong RF injection at the laser cavity round-trip frequency of 14.3~GHz and are continuously tuned in frequency by varying the laser drive currents. This enables continuous spectral sampling over a 32~cm$^{-1}$ range centered near 8~\textmu m, with an effective sampling interval of approximately 80~MHz. The outputs of both combs are coupled into the same monolithically integrated light coupler, providing automatic collinear alignment before the combined beam interrogates the sample. We benchmark the spectrometer against an external-cavity tunable laser and validate its performance using HITRAN simulations for 1.25% nitrous oxide. Finally, the unidirectional comb architecture suppresses the detrimental effects of optical feedback, yielding comparable residuals even under deliberately introduced strong feedback. More broadly, the benefits of miniaturization extend beyond reduced footprint: chip-scale integration enables new forms of electrical and optical control that can fundamentally change how dual-comb spectrometers are operated.
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All authors Johannes Fuchsberger, Theodore P. Letsou, Paul Chevalier, Marcus Ossiander, Dmitry Kazakov, Federico Capasso, Benedikt Schwarz

Optics · Cross-listed from physics.app-ph

Transient Dynamics and Duty-Cycle Optimization in a Pulse-Wwidth Modulation Bell–Bloom Pumping

Ying-Hao Ye, Ling-Yan Hu, Dui-Gao Yi et al. (+2 more)

We investigate the duty-cycle-dependent atomic response under full-depth intensity pulse-width modulation in Bell–Bloom optical pumping. A time-domain Bloch model explicitly resolves the pump-on/off spin dynamics, yielding piecewise analytical transient solutions and a periodic steady-state description without cycle averaging or harmonic truncation. An extended free-induction-decay method independently determines the effective dark and pump-on transverse-relaxation rates, $W_0$ and $W$. The predicted lock-in responses agree well with experimental results. We find that for each Larmor frequency $\omega_0$, the slope is maximized at a finite pump rate that increases with $\omega_0$. These results provide a practical framework for sensitivity-oriented optimization of the duty cycle and pump rate in PWM-driven atomic magnetometers.
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All authors Ying-Hao Ye, Ling-Yan Hu, Dui-Gao Yi, Zhi-Fei Yu, Bing Chen

Optics · Cross-listed from quant-ph

Fock-state filtering of squeezed states: enhanced nonclassicality and effects of a thermal bath

João Pedro Gonzalez de Oliveira and A. Vidiella-Barranco

The ability to tailor photon-number statistics is central to the generation and control of nonclassical states of light. Here, we investigate how Fock-state filtering of squeezed coherent states can be used to engineer their photon statistics. We consider the selective removal of the $m=0$ and $m=1$ Fock components and show that this process can enhance the sub-Poissonian character of the field, depending on the coherent amplitude. We then analyze the evolution of these engineered states in a thermal environment. Although all states eventually relax toward thermal statistics, the signatures of the filtering process may persist over a significant part of the evolution, while the purity of the filtered states is rapidly degraded by incoherent population redistribution. Our results illustrate both the potential and the limitations of photon-number engineering in realistic, dissipative settings.
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Sunday 23 August

Optics · Cross-listed from physics.plasm-ph

Early-Time Reshaping of Laser-Induced Plasma Profiles

Ivan Ostrovsky, Gilad Hurvitz, Soumitra Hazra et al. (+1 more)

Laser-induced plasmas are primarily characterized by their temporal density decay. Using time-resolved transverse optical diffractometry, we reveal their concurrent spatial evolution, demonstrating pronounced broadening and flattening during the first 200 ps following ionization. This non-self-similar evolution arises from the local density dependence of electron-ion recombination, without particle transport. Exploiting the continuum of initial densities within a single plasma disc, we experimentally reconstruct an effective, time-dependent local recombination law over a broad density range. Applied locally to independently measured initial plasma profiles, this kinetic map quantitatively predicts their subsequent evolution. These results are relevant to transient diffractive optics, plasma-based optical elements and waveguides, and the development of laser-induced plasmas as platforms for gas-phase THz plasmonics.
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All authors Ivan Ostrovsky, Gilad Hurvitz, Soumitra Hazra, Sharly Fleischer

Optics

Chebyshev self-imaging from inverse-sampled angular spectra

Layton A. Hall and Murat Yessenov

For nearly two centuries, conventional self-imaging has obeyed a single rule: a periodic wave reconstructs itself at a fixed distance, independent of its bandwidth. Here we show this law is programmable. Sampling the angular spectrum in inverse powers of the mode index makes each mode rephase with its own integer period, deferring exact revival to the least common multiple of all periods: $z_{\mathrm{rev}}=z_{\mathrm{T}}\,e^{r\psi(M)}$, with $\psi$ the second Chebyshev function. We observe these revivals optically as a prime-power staircase in propagation distance, turning free-space diffraction into a readout of the multiplicative structure of the integers.
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Optics

Diagonalizing an optical coherence matrix via on-chip Stokes tomography

Amin Hashemi, Abbas Shiri, Bahaa E.A. Saleh et al. (+2 more)

Structured coherence – partially coherent light spanned by a finite number of modes – is emerging as a powerful tool in optical communications, computation, cryptography, and spectroscopy. Key to these prospects is the recent development of on-chip processing of structured coherence, in which large meshes of interferometers implement unitary and non-unitary transformations on the Hermitian coherence matrix representing multimode partially coherent light. Two related critical tasks for the applications of structured coherence are the reconstruction of an unknown coherence matrix and its diagonalization. Stokes tomography has been utilized in reconstructing the coherence matrix, whereas variational processing has been employed in its diagonalization. We show here that Stokes tomography can also be exploited in the on-chip diagonalization of an unknown coherence matrix, which we verify for two-mode and four-mode structured coherence in an integrated hexagonal mesh of Mach-Zehnder interferometers. This photonic circuit implements a predetermined sequence of configurations to estimate the generalized Stokes parameters, which – in a final step – inform a reconfiguration of the photonic circuit that diagonalizes the coherence matrix. The field is thus left in a coherent-mode representation comprising uncorrelated, orthogonal modes whose weights correspond to the eigenvalues of the original coherence matrix. Moreover, the integrated photonic circuit can be configured to provide the original field alongside its diagonalized counterpart at the circuit output. We verify the diagonalization procedure for coherence matrices of different coherence rank, entropy, and structure. Finally, we dispel the common notion that O(N^2) steps are required for reconstructing an N x N coherence matrix and show that only O(N) steps are needed.
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All authors Amin Hashemi, Abbas Shiri, Bahaa E.A. Saleh, Andrea Blanco-Redondo, Ayman F. Abouraddy

Optics · Cross-listed from cond-mat.mes-hall

Coordinate transformations and matter waves cloaking

Reza G. Mohammadi, Ali G. Moghaddam and Ramin Mohammadkhani

Transformation method provides an efficient tool to control wave propagation inside the materials. Using the coordinate transformation approach, we study invisibility cloaks with sphere, cylinder and ellipsoid structures for electronic waves propagation. The underlying physics behind this investigation is the fact that the Schrödinger equation with position-dependent mass tensor and potentials has a covariant form that follows the coordinate transformation. Using this technique we obtain the exact spatial form of the mass tensor and potentials for a variety of cloaks with different shapes.
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Saturday 22 August

Optics

Dynamically twistable three-dimensional moiré photonic crystals

Henri Lemineur, Abhishek Padhy, Nicolas Roy et al. (+2 more)

Three-dimensional woodpile photonic crystals constitute one of the most successful architectures for realizing photonic band gaps, yet their optical response is traditionally fixed by the geometry established during fabrication. Here, we introduce a twist-controlled woodpile photonic crystal in which the relative angular orientation between successive rod layers acts as an additional, in situ-tunable geometrical degree of freedom. Using an extension of rigorous coupled-wave analysis adapted to multilayer structures with rotated reciprocal lattices, we systematically investigate the evolution of the transmission spectrum as a function of twist angle. We show that twisting drives the structure through three distinct photonic regimes. In the fully aligned configuration, broad frequency intervals exhibit near-unity transmission. At intermediate twist angles, the spectrum becomes populated by strongly dispersive resonances displaying characteristic Fano line shapes, high quality-factor and pronounced angular sensitivity. As the twist angle approaches 90{\deg}, the conventional woodpile structure is recovered, and these resonances evolve into a broad photonic stop band characteristic of three-dimensional photonic crystals. A simplified analytical model based on reciprocal-lattice considerations accurately reproduces the principal resonance modification observed in the numerical calculations. Our results demonstrate a continuous twist-induced transition from broadband transmission to photonic stop bands through an intermediate Fano-resonant regime, establishing twisted woodpiles as a versatile platform for three-dimensional twist-engineered photonics.
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All authors Henri Lemineur, Abhishek Padhy, Nicolas Roy, Benoit Hackens, Michaël Lobet

Optics

Mie Optical Computing

Vsevolod Kleshchenko, Vladimir Igoshin, Costantino De Angelis et al. (+1 more)

Optical computing is emerging as a promising paradigm for next-generation information processing. Diffractive optical processors rely on spatially distributed trainable degrees of freedom, leading to extended architectures. Here, we propose a compact neuromorphic optical-computing approach where the entire trainable transformation is implemented by a single Mie scatterer. By formulating computation in vector spherical harmonics basis, trainable modal couplings can be concentrated within a finite object through its T-matrix. Since available T-matrix parameters scale as the fourth power of maximal multipole order, this architecture can overcome trainable-parameter-density limitations of conventional spatially distributed diffractive processors. We demonstrate classification of phase-encoded MNIST images using scattered-field intensity. At a particle size parameter of $ka = 15$, the trained T-matrix reaches approximately 90% test accuracy, comparable to a single-layer artificial neural network. Similar performance can be achieved using near-fields, enabling on-chip integration. We show how reciprocity, passivity, and particle symmetry constrain performance: passivity reduces the accessible operator space while improving robustness, whereas symmetry reduces the number of independent parameters. Finally, we inverse-design a non-absorbing dielectric scatterer that realizes the classification task with 84% accuracy. These results demonstrate that nontrivial neuromorphic transformations can be encoded within the multipolar response of a single compact scatterer.
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All authors Vsevolod Kleshchenko, Vladimir Igoshin, Costantino De Angelis, Mihail Petrov

Optics

Feature-domain Fourier ptychographic tomography with dark-field illumination

Chao Tan, Fangrui Lu, Sechan Park et al. (+6 more)

Fourier ptychographic tomography (FPT) is an implementation of intensity diffraction tomography that reconstructs three-dimensional (3D) refractive-index (RI) distributions from angle-varied intensity measurements. The distinctive advantage of FPT emerges when incorporating dark-field illumination, which extends the space-bandwidth product toward gigavoxel-scale volumetric imaging, yet dark-field measurements are highly sensitive to system imperfections and often have low signal-to-noise ratios. Here, we propose feature-domain FPT (FD-FPT), which evaluates data fidelity after feature extraction and is optimized using automatic differentiation. In numerical and experimental tests, FD-FPT resolves structures near the synthetic-aperture cutoff far more reliably than the spatial-domain baseline (SD-FPT). Notably, in a whole-mount Oedogonium specimen, the reticulate chloroplast network and transverse septa were resolved only by FD-FPT. We further demonstrate a 1.81-gigavoxel RI reconstruction of a mouse adrenal gland section across a 1.66 by 1.40 square millimeter field of view, establishing FD-FPT as a practical route to label-free volumetric imaging that combines millimeter-scale coverage with cellular-scale structural contrast.
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All authors Chao Tan, Fangrui Lu, Sechan Park, Hyeonseo Na, Chanseok Lee, Chang-Seok Kim, Jeesu Kim, Hwidon Lee, Mooseok Jang

Optics · Cross-listed from physics.ins-det

An integrated micro-thermometer for mid-infrared photothermal spectroscopy of dense materials built in a CMOS 200 mm pilot line

Sandy Mathew, Sonia Messaoudène, Adrien Poizat et al. (+6 more)

Indirect photothermal infrared spectroscopy of dense materials typically relies on photoacoustic cells for detecting acoustic waves generated by light-induced heating. This detection approach can be challenging to implement as it is highly sensitive to the sealing quality of the interface between the cavity and the sample, as well as to the properties of the gas within the cavity. Here, we present a simplified and more robust method. This approach relies on direct photothermal temperature measurement using an optimized platinum microsensor fabricated on a thin silicon substrate that acts as a thermally transparent interface with the sample. The sensor design, fabrication in a 200 mm CMOS pilot line, assembly on a readout PCB, and experimental characterization are reported. The component achieves a signal-to-noise ratio close to 1000 making it well-suited for miniaturized and embedded infrared spectroscopic applications.
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All authors Sandy Mathew, Sonia Messaoudène, Adrien Poizat, Éléa Bourliaud, Marion Volpert, Jules Skubich, Stanislas Lhomme, Bertrand Bourlon, Kevin Jourde

Optics

Critical Topological Photonics in Synthetic Dimensions

Mingyuan Chen, Yuwei Jing, Franco Nori et al. (+1 more)

Topological states and criticality have long been regarded as incompatible ingredients: the former requires a finite spectral gap, whereas the latter demands its closure. Guided by this view, topological photonics has focused almost exclusively on gapped phases, treating gap-closing transitions as mere phase boundaries. In this work, we propose a class of topological states in which topology coexists with criticality in experimentally accessible synthetic-frequency photonic platforms. In a one-dimensional (1D) synthetic lattice, we identify such critical topological photonic states through midgap degeneracies in the single-particle entanglement spectrum, and uncover a topology-enforced multicritical point that reorganizes the topology of neighboring critical states. We further extend this framework to two dimensions (2D). Our work provides an experimentally accessible route to critical topological photonics, and may also inspire novel applications such as critical topological sensing.
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All authors Mingyuan Chen, Yuwei Jing, Franco Nori, Xue-Jia Yu

Optics

Coexistence of Magnon-Induced Optical Vortex and Gaussian Beam Scattering Assisted by Rotational Umklapp Process

Ryusuke Hisatomi, Kotaro Taga, Hisakazu Matsuki et al. (+3 more)

The exploitation of crystal-lattice symmetries to engineer angular momentum transfer between structured light and magnons marks a novel frontier for optomagnonic research. In Brillouin light scattering, when focused light propagates parallel to an external magnetic field and interacts with ferromagnetic uniform magnons, only optical-vortex scattering is expected to be permitted. Due to the combined effects of magneto-optical coupling and optical spin-orbit interaction, the transfer of magnon spin angular momentum to photon orbital angular momentum allows for this distinctive scattering phenomenon. Here, we experimentally demonstrate that, for a specific ferromagnetic crystal orientation, Gaussian-beam scattering coexists with the optical-vortex scattering, contrary to conventional expectations based on angular momentum conservation between magnons and photons. We show that the crystal lattice, via the rotational Umklapp process, provides the missing angular momentum required for the Gaussian-beam scattering. Furthermore, we predict that as the degree of light focusing increases, the relative efficiencies of the Gaussian-beam and optical-vortex scattering processes reverse.
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All authors Ryusuke Hisatomi, Kotaro Taga, Hisakazu Matsuki, Shutaro Karube, Yoichi Shiota, Teruo Ono

Optics · Cross-listed from quant-ph

Reinventing the Single-pixel Imaging Paradigm via Quantum-Operator-Based Signal Processing

Bu-Ran Yu, Yi-Zhu Zhang, Kan-Xu Jia et al. (+3 more)

A fundamental bottleneck across modern computational imaging and high-dimensional sensing is the conventional decoupled acquisition-reconstruction hierarchy, which subjects high-dimensional spatial sensing to the classical shot-noise limit and intense computational overhead. As a prominent manifestation of this limitation, single-pixel imaging (SPI) suffers severely from this paradigm. We reinvent this paradigm by introducing a quantum-operator-based SPI theoretical framework driven by coherent signal processing. Within this architecture, the spatial inverse problem is analytically mapped into the eigenvalue spectrum of a quantum operator via tailored light-matter interactions. By analytically synthesizing non-linear reconstruction operators via ultra-shallow quantum architectures, we theoretically demonstrate an exponential decay of spatial approximation errors, completely bypassing traditional linear solvers. This operator-space embedding not only shields reconstruction from noise via a strategic error-saturation zone but also bridges the gap from classical shot-noise scaling $\mathcal{O}(1/\sqrt{N_{\text{ph}}})$ to the ultimate Heisenberg limit $\mathcal{O}(1/N_{\text{ph}})$. Crucially, while formulated within SPI, this coherent operator paradigm fundamentally extends to general photon-starved, high-dimensional imaging modalities. This work establishes a universal theoretical blueprint for next-generation quantum-enhanced sensing, shifting the paradigm from iterative optimization to coherent operator-space evolution.
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All authors Bu-Ran Yu, Yi-Zhu Zhang, Kan-Xu Jia, Qian-Qian Bao, Shao-Ying Meng, Xi-Hao Chen

Optics · Cross-listed from cond-mat.soft

Pitch-controlled reorientational nonlinearity in chiral nematic liquid crystals: a reduced-order model for self-focusing and soliton formation

Homa Saadatmand, M. Javad Zakeri, Ahmed Sameh Ahmed et al. (+6 more)

We present a reduced-order semi-analytical model for reorientational nonlinearity in chiral nematic liquid crystals, showing that the chiral pitch acts as the dominant physical length scale governing the onset of nonlinear self-focusing and soliton formation. Starting from the full Frank-Oseen equation, we derive a closed-form expression for the optically induced molecular rotation that captures the essential saturable response of the medium while reducing computational cost by more than two orders of magnitude compared with standard relaxation-method solvers. Despite its simplicity, the model reproduces the essential features of the numerically obtained nonlinear refractive index, the onset of self-localization, and the transition from discrete to continuous solitons in one and two dimensions. It further predicts the formation of fully localized astigmatic nematicons with only minor shifts in the self-localization threshold due to the neglect of nonlocal effects. The proposed model provides direct physical insight into light-matter interactions with soft matter media and offers a computationally efficient tool for the design and optimization of nonlinear photonic devices.
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All authors Homa Saadatmand, M. Javad Zakeri, Ahmed Sameh Ahmed, Suraj Bhandari, Loubna Benkoula, Ameer B. Batarseh, Andrea Blanco-Redondo, Miroslaw Karpierz, Pawel S. Jung

Friday 21 August

Optics · Cross-listed from physics.gen-ph

Field-Deployable Pressure Standard Based on a Compact Dual-Cavity Refractometer

Zhong-Liang Nie, Jin Wang, Zi-Fan Zhao et al. (+2 more)

The next-generation pressure standard is moving toward optical-based, field-deployable systems. However, most existing optical refractometry pressure standards rely on bulky ultra-low expansion (ULE) cavities and complex feedback locking, limiting their portability and on-site applicability. Here, we present a miniaturized, transportable optical pressure manometer based on a dual-channel Fabry-Perot cavity machined from a single block of common fused silica. By employing a differential measurement between an evacuated reference cavity and a gas-exposed measurement cavity, common-mode errors such as thermal expansion and pressure-induced deformation are largely canceled, enabling the use of low-cost fused silica to achieve performance comparable to ULE. Radio-frequency scanning with Lorentzian fitting replaces conventional feedback locking, simplifying the optical design and improving robustness. Calibrated against a piston manometer, the device demonstrates a measurement repeatability of 3.4~ppm and a total uncertainty of \(u = \sqrt{(10.6\times10^{-6}p)^2 + (5.4~\mathrm{mPa})^2}\). The system can resolve periodic pressure fluctuations originating from the piston manometer and exhibits superior response speed. With its small footprint, portability, and independence from external frequency references, this fused-silica dual-cavity manometer offers a practical route toward on-site, quantum-traceable pressure calibration.
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All authors Zhong-Liang Nie, Jin Wang, Zi-Fan Zhao, Chang-Le Hu, Shui-Ming Hu

Optics

Simultaneous Intensity and Frequency Control for Optical Waveform Generation using an Acousto Optic Modulator

Hariprasad Madathil, Shengzhi Wang and F. Elohim Becerra

We describe a method for calibrating the response of an acousto-optic modulator (AOM) to enable precise, arbitrary control of the intensity and frequency of optical fields. The method involves characterizing the nonlinear response of the AOM to its input RF drive voltage and applying an iterative calibration/correction algorithm to accurately map input RF amplitude and frequency drive to output optical intensity and frequency shifts. After a few calibration/correction iterations, the calibration of the AOM maintains the optical power within 1$\%$ of a constant target value over relatively wide frequency tuning range ($\approx$100 MHz), with $\sigma=0.2\%$ relative deviation. We apply this calibration method to generate programmable waveforms and optical pulses with tailored intensity and frequency profiles that closely match their target specifications. This technique offers a simple and robust method for applications that require high-accuracy optical modulation.
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Optics · Cross-listed from quant-ph

Increased cyclicity of atomic transitions via coherent interference of decay paths

Eliza Cornell, Benjamin Pingault, Gergő Thiering et al. (+3 more)

Optical readout is a fundamental tool in atomic state measurement, yet the fidelity of optical readout is frequently limited by imperfect photon collection. This can be mitigated when readout occurs on a cycling transition which continuously fluoresces under resonant excitation, thus increasing signal and enabling single-shot readout. We present a method to extend the cyclicity of atomic transitions via coherent destructive interference between spurious decay paths. We describe the characteristics of atomic systems in which this method can be implemented and model several examples in which the number of emitted photons is increased by multiple orders of magnitude.
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All authors Eliza Cornell, Benjamin Pingault, Gergő Thiering, Neil Sinclair, Ádám Gali, Marko Lončar

Optics

Machine Learning to Foundation Models: Artificial Intelligence for Nanophotonic Modeling and Scientific Discovery

Chaobin Yang, Xueqing Liu, Yiqun Fu et al. (+4 more)

Artificial intelligence (AI) is increasingly used to model, design, and study nanophotonic systems. This review traces the development of the field from classical machine learning and deep learning to generative models, transfer learning, transformers, and emerging foundation models. It first introduces major nanophotonic platforms, including nanoparticles, nanoholes, metasurfaces, photonic crystals, multilayer thin films, and integrated photonic devices, together with their main forward and inverse problems. It then reviews data-driven methods for predicting optical spectra and fields, generating structures from target responses, improving designs through optimization, and accounting for fabrication constraints. Generative models are discussed as a way to produce multiple valid solutions to nonunique inverse problems, while transfer learning, few-shot learning, and physics-aware training help reduce data requirements and improve generalization. Recent domain-specific foundation models show that different optical structures and responses can be handled within shared representations, but current systems remain limited in scope and physical grounding. Future progress will depend on multimodal models that connect geometry, materials, spectra, electromagnetic (EM) fields, fabrication data, experiments, and scientific literature with reliable simulation and validation tools. Current foundation models remain domain-specific, and their extension to broader nanophotonic tasks will require stronger physical grounding and validation.
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All authors Chaobin Yang, Xueqing Liu, Yiqun Fu, Fengbo Zhou, Krzysztof Kempa, Stefano Anzellotti, Michael J. Naughton

Optics · Cross-listed from quant-ph

Emulating non-Markovian system-bath dynamics with parametrically driven cavities

Valentin Boettcher, Félix Pellerin, Philippe St-Jean et al. (+1 more)

We introduce and characterize a scheme for emulating non-Markovian quantum system-bath dynamics using the discrete electromagnetic field modes of a parametrically driven cavity. In this scheme, the character of a bosonic bath (the form of the bath spectral density) is tied directly to the shape of the real-time waveform describing periodic parametric cavity modulation. As an explicit example, we demonstrate the feasibility of this scheme for a fiber-loop experiment with currently achievable parameters, supported by numerical simulations and analytical estimates. In particular, we show that a localization transition of the spin-boson model can be accurately emulated in this fiber-loop cavity system. This localization effect is characterized by a sharp transition from partial decay to complete decay for a two-level system coupled to a bosonic bath as the bath spectral density $J(\omega)\propto \omega^{s}$ is continously tuned from the sub-ohmic ($s<1$) to the super-ohmic ($s>1$) regime. The transition is only exactly realized in the thermodynamic limit (for an infinite number of bath modes) and for sufficiently weak system-bath coupling. We highlight a competition between the weak-coupling and thermodynamic limits in this problem and show that challenges in approximately realizing the transition can nevertheless be overcome. Finally, we provide bounds on the systematic error introduced when emulating non-Markovian dynamics for arbitrary system observables. The scheme presented here can enable the realization of a modular platform for engineering custom non-Markovian baths, with potential applications in quantum thermodynamics, thermalization of many-body systems, and resource-efficient quantum simulations of open quantum systems.
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All authors Valentin Boettcher, Félix Pellerin, Philippe St-Jean, William A. Coish

Optics

Weyl Points and Fermi Arc Surface States in a Self-assemblable Zinc-Blende Photonic Crystal

Johnathon P. Gales, Hengbin Cheng, David J. Pine et al. (+1 more)

Colloidal self-assembly has long been proposed as a method for growing large-scale three-dimensional photonic crystals with important optical properties in visible and near-infrared wavelength regimes, where top down lithographic fabrication fails. While much of the focus in these systems has been on producing a photonic band gap, such lattices can also give rise to topological features of photonic bands. To date, there has been no proposal for realizing topological photonic features in photonic crystals that may be self-assembled. In 3D, Weyl points are topological band degeneracies that are of particular interest due to their robustness to perturbations and their corresponding Fermi arc surface states. In order to realize Weyl points, either time-reversal or inversion symmetry must be broken, and no previous self-assembled colloidal photonic crystal has exhibited either property. Here, we propose a new zinc-blende structure, built off of recent progress in self-assembling diamond photonic crystals, which lacks inversion symmetry and supports photonic Weyl points. Furthermore, we show that the geometry can be optimized to make the Weyl point and its Fermi arc surface states experimentally observable in the photonic crystal's projected band structure. Finally, we perform molecular dynamics simulations to demonstrate that the geometry we propose for observing Weyl points is capable of being self-assembled with realistic interparticle interactions. Together, these results provide a platform for the assembly of large-scale photonic crystals supporting topological degeneracies and robust Fermi arc surface states in the visible and near-infrared.
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All authors Johnathon P. Gales, Hengbin Cheng, David J. Pine, Mikael C. Rechtsman

Optics

Optical injection locking of white light cavity based superluminal lasers

Jacob Scheuer, Zifan Zhou, Yael Sternfeld et al. (+2 more)

Optical injection locking is a simple method for synchronizing a laser to an external laser source by injecting part of the external laser light into the cavity of the other laser. This approach received significant interest due to its potential applications in telecommunications, precision metrology, and more. We study and analyze the steady-state and dynamic properties of optical injection locking in white light cavity (WLC) lasers. We derive the steady-state injection locking range of the WLC laser and the dynamic (Adler) equation for the phase-difference between the injected signal and the locked laser output. The analysis shows that WLC lasers can exhibit an order of magnitude broader locking range and three order of magnitudes faster dynamics compared to conventional lasers with similar thresholds and free spectral ranges.
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All authors Jacob Scheuer, Zifan Zhou, Yael Sternfeld, Michal Hazan, Selim M. Shahriar

Optics

Femtosecond Laser Induced Metallization in Silicon via Photon Momentum Mediated Band Transition

Ehatasham Haque, Sunjana Tarannum, Jannatul Shahrin Shoshi et al. (+1 more)

Silicon-based technology has been at the forefront of electronic and photonic research since the dawn of the electronic revolution. However, silicon is fundamentally an indirect-bandgap semiconductor: the conduction band minimum and valence band maximum occur at different points in momentum space, so optical transitions require phonon assistance to conserve crystal momentum. This three-body electron-photon-phonon interaction renders silicon an inefficient material for light-absorbing applications such as solar cells and optoelectronic devices. In this work, we build on an established nanoscale photon-momentum confinement mechanism, which broadens the photon momentum distribution and enables phonon-free absorption in silicon, by subsequently applying a high-intensity femtosecond pulsed excitation that injects hot carriers beyond the Mott density, collapsing the bandgap and inducing a reversible semiconductor-to-metal transition. While nanoscale photon-momentum confinement itself has been previously established, the central contribution of this work is this subsequent, carrier density-driven stage, which drives the momentum-enhanced region into a reversible transient metallic phase. Our simulations report highly negative permittivity, enhanced optical power absorption, a large absorption coefficient, and low skin depth, with carrier densities reaching a notable value, far exceeding the Mott threshold. We have shown carrier driven metallization with stable operation below melting threshold of silicon. These results establish a general mechanism for dynamically inducing metallic states in silicon, offering a potential pathway toward monolithically integrated active photonic components and dynamically reconfigurable electro-optical devices within conventional CMOS platforms.
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All authors Ehatasham Haque, Sunjana Tarannum, Jannatul Shahrin Shoshi, Mahdy Rahman Chowdhury