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Physics Physics Optics

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Monday 28 September

Optics

Tensor-Engineered Van der Waals NbOCl2 Resonant Metasurface for Polarization-entangled Bell State Generation

Xin Zeng, Wenna Du, Yun-Kun Wu et al. (+20 more)

Polarization-entangled photon pairs are essential resources for quantum information technologies, yet realizing compact sources with intrinsically controllable entanglement remains challenging. Van der Waals (vdW) nonlinear materials such as NbOCl2 provide atomically thin platforms for quantum light generation, yet their native crystalline anisotropies as natural materials impose limitations on accessible quantum states. Here, we develop a resonant vdW nonlinear metasurface based on NbOCl2 that exploits its intrinsic optical anisotropy to engineer polarization-dependent nonlinear responses. The anisotropic optical dispersion enables selective manipulation of resonant modes, resulting in a three-order-of-magnitude enhancement of the nonlinear response along the c axis. By further tailoring these resonant modes, we redistribute the effective second-order nonlinear susceptibility tensor between orthogonal polarization channels, balancing the spontaneous parametric down-conversion pathways along the b and c axes. This enables polarization-entangled photon generation with a measured fidelity of up to 92%. Our work establishes metasurface-enabled nonlinear optical engineering as a strategy for enhancing and controlling quantum light generation in vdW materials, providing a pathway toward scalable quantum photonic platforms.
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All authors Xin Zeng, Wenna Du, Yun-Kun Wu, Yuyang Zhang, Zhiyong Zhang, Kwok Kwan Tang, Ruihuan Duan, Xiaotian Bao, Yiyang Gong, Yuexing Xia, Yutong Zhang, Jinhan Zhao, Yubo Tian, Yangguang Zhong, Chuanxiu Jiang, Yubin Wang, Jianhui Fu, Shuai Yue, Guankui Long, Qing Zhang, Zheng Liu, Xi-Feng Ren, Xinfeng Liu

Optics

Multimode oscillation and its route to chaos in transverse-mode-coupled optomechanical resonators

Motoki Asano, Lalit Maharjan and Hiroshi Yamaguchi

Nonlinear oscillators exhibit rich collective phenomena including synchronization, bifurcation, and chaos. Experimentally accessing multimode nonlinear dynamics, however, remains challenging because low-order internal resonances readily induce mode locking and suppress stable multimode oscillation. Here, we demonstrate a transverse-mode-coupled optomechanical platform that combines engineered collective mechanical modes with optically controllable nonlinear interactions. The engineered transverse mechanical modes enable stable two- and three-mode self-sustained oscillations while suppressing trivial low-order internal resonances. By varying the laser frequency, we observe successive beat-frequency fractionalization ({\Delta}f/2 and {\Delta}f/3), followed by a broadband state exhibiting enhanced trajectory divergence consistent with deterministic chaos. These results establish transverse-mode-coupled optomechanical resonators as a scalable and tunable platform for exploring high-dimensional nonlinear dynamics in interacting mechanical networks.
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Sunday 27 September

Optics

Tapered Fibre Fabry-Pérot Cavities for the Generation of Near-Visible, Phase-locked, and Broadband Kerr Frequency Combs

Matthew Macnaughtan, Yiqing Xu, Miro Erkintalo et al. (+2 more)

We demonstrate the generation of near-visible, broadband Kerr frequency combs using a tapered fibre Fabry-Pérot resonator. By incorporating micron-diameter tapered silica fibre into a pulsed-driven Fabry-Pérot configuration, we exploit geometric dispersion engineering to overcome the strong normal dispersion intrinsic to silica (and nearly all materials) at short wavelengths, achieving net anomalous dispersion in the near-visible regime. The strong mode confinement of the tapered fibre simultaneously enhances the Kerr nonlinearity by over an order of magnitude relative to standard fibre, substantially reducing the threshold drive power for nonlinear structure formation. Through precise control of the cavity fabrication, we experimentally demonstrate and numerically confirm a rich suite of coherent, phase-locked nonlinear structures, including conventional anomalous dispersion cavity solitons, zero dispersion solitons with spectral bandwidths exceeding 16 THz between 750 nm and 800 nm, as well as switching wave combs and broadband Raman solitons, the latter also reported here for the first time in the near-visible regime. Our results establish the tapered fibre Fabry-Pérot resonator as a versatile platform for near-visible and potentially visible coherent frequency comb generation.
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All authors Matthew Macnaughtan, Yiqing Xu, Miro Erkintalo, Stéphane Coen, Stuart G. Murdoch

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

Topological chiral edge modes in the continuum of a trivial bulk

Li Ge

Chiral edge modes in topological states of matter are routinely found inside band gaps, which may be deformed and shifted as a function of the lattice momentum. Here we show that they can exist inside a bulk band instead, i.e., in the continuum. These chiral edge modes in the continuum (CEMICs) are induced by introducing an imaginary magnetic flux to an otherwise topologically trivial two-dimensional system, realized by imposing asymmetric couplings along the edge. While the stronger couplings provide a preferred circulation direction, we find that the edge localization of CEMICs does not originate from the non-Hermitian skin effect, which is typically associated with systems featuring asymmetric couplings and the open boundary condition. Instead, this edge localization is due to the energy exchange between the system and the environment at the asymmetric coupling junctions, which leads to a parity-time (PT) transition in the Brillouin zone. Intriguingly, the onset of CEMICs is independent of the system size in the macroscopic limit, which is given by the golden ratio between the asymmetric couplings and their geometric average.
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Optics

Multi-Aperture PPG with MAPIS: Spatial Optical and Temporal Coherence Fields

Shuguang Wang and Yuanjing Wang

Conventional reflectance photoplethysmography (PPG) typically reduces tissue optical responses to one or a few detector channels. Matrix Pinhole Image Sensing (MAPIS) instead simultaneously samples multiple aperture-dependent optical signals. We analyzed 44 recordings of 30 seconds each from a single MAPIS device to characterize the spatial relationships among DC intensity, pulsatile AC, perfusion index (PI), and temporal coherence across Red and infrared channels. AC increased sublinearly with DC at both wavelengths, resulting in higher PI toward lower-DC apertures, consistent with a first-order relative path-sensitivity interpretation. A second counterintuitive spatial trend was observed in temporal coherence: lower-DC and lower-AC apertures exhibited higher autocorrelation and greater cardiac-periodic spectral concentration. IR signals also showed consistently higher temporal coherence than corresponding Red signals. These observations demonstrate that multi-aperture PPG resolves reproducible spatial relationships among optical intensity, fractional pulsatile sensitivity, and waveform coherence that are largely averaged together in conventional single-channel PPG. The present study establishes within-device relationships and motivates controlled studies of the underlying photon-path mechanisms.
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Optics

Supergaussian pulse distortion in single-mode fibers with arbitrary dispersion

Jose Capmany

Marcuse theory of pulse distortion in singlemode fibers provides closed-form results for Gaussian pulses launched from sources of arbitrary spectral width. We extend the theory to supergaussian pulses of arbitrary order with linear or edge-concentrated chirp, single or multiline sources and an arbitrary number of dispersion coefficients. The rms output width is obtained exactly from the moments of the Wigner distribution, and all the pulse moments involved reduce to finite sums of Gamma functions. Supergaussian pulses are considerably more sensitive than Gaussian pulses to higher order dispersion and are compressed less efficiently by chirp. Near the zero-dispersion wavelength their rms width is governed by weak spectral side lobes and overestimates the broadening of the pulse energy. For pulse sequences, interference between neighboring pulses leaves all time moments unchanged when the input pulses do not overlap, but it redistributes energy locally with a visibility set by the source spectrum filtered by the pulse spectrum.
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Optics

Propagation of pulse fluctuations of multimode sources in optical fibers and waveguides with arbitrary chromatic dispersion

José Capmany

We extend Marcuse analysis of pulse fluctuations of randomly phased multimode sources to arbitrary chromatic dispersion, chirp, finite mode linewidth, mode partition noise and finite receiver bandwidth. On long fibers the fluctuations depend only on the shape of the group delay curve, a monotonic delay separates the modes, whereas a symmetric delay leaves pairs of modes with identical intensity profiles and a persistent beat noise. Dispersion downconverts the beats of overlapping modes to baseband, where receivers cannot filter them. The detected power follows random phasor statistics, and Gaussian estimates of fade probability can be wrong by orders of magnitude. Mode partition noise grows with dispersion and dominates in band limited links.
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Optics

Tailored multipolar optical trapping with higher-order structured light

Nabendu Mishra, Nick Vamivakas and Eileen Otte

Dipolar optical forces can confine Rayleigh-sized dielectric particles towards or away from intensity maxima, commonly known as bright and dark trapping. Structured light illumination opens up opportunities for customized trapping landscapes, unveiling the possibility of gray trapping, especially for larger Mie particles that can excite a higher-order multipolar response. While previous studies have primarily focused on calculations of the gradient force for some exemplary, focused scalar beams, we not only extend these analyses by combining vectorial focusing with generalized Lorenz-Mie theory, but also consider more complex trapping fields. Motivated by their unique tight focusing behavior, shaping strong transverse intensity gradients and three-dimensional electric field components, we explore higher-order cylindrical scalar and vector beams. We theoretically investigate multipolar trapping of Mie-regime silicon nanospheres in water, calculating the three-dimensional net radiation force and assess local trapping stability through the force Jacobian. Near an octupolar Mie resonance, we predict stable gray trapping with enhanced efficiency for vector beams. Further, we find field geometries enabling configurable, particle-size-dependent gray/dark trapping with subwavelength inter-particle spacing. These results establish polarization, illumination structure and particle parameters as complementary controls for radius-dependent multipolar trapping, providing a basis for potential applications in sub-wavelength particle sorting, trapping-assisted nanopatterning and optical binding investigations.
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Optics

Optical Möbius Snails

Qiang Wang, Pedro A. Quinto-Su, Xi Xie et al. (+3 more)

The exploration of topological states has emerged as a vibrant frontier across diverse physical systems. Among these, the Möbius strip stands out as a canonical structure that has recently inspired intriguing optical physics.In this work, we extend this concept into the high-dimensional realm by using an optical analogue-the optical Möbius snail. Specifically, employing a skyrmionic beam as the input field, tight focusing yields a continuous family of Möbius strips that exists in three-dimensional space, giving rise to a snail-like polarization topological texture. Furthermore, we demonstrate full-field polarization tomography and achieve switchable control of this optical snail texture by tuning the Skyrme number of the incident skyrmionic beam. Our findings establish a direct bridge between low- and high-dimensional Möbius geometries, opening a new platform for exploring complex spatial topology and tailored light-matter interactions.
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All authors Qiang Wang, Pedro A. Quinto-Su, Xi Xie, Xiangsheng Xie, Chenghou Tu, Yijie Shen

Optics · Cross-listed from cond-mat.mtrl-sci

Unifying Magnetic, Electrical, and Thermoelectric Responses in a Non-Collinear Antiferromagnet

André José, Adrielson Dias, Carlos Eduardo et al. (+6 more)

Non-collinear antiferromagnets offer unconventional routes for controlling magnetic, electrical, and thermoelectric responses through their complex spin configurations and interfacial symmetry. Here, we detect exceptional interfacial properties arising from a non-collinear antiferromagnet by demonstrating a robust and quantitatively consistent exchange-bias response in an IrMn$_3$/Py heterostructure. The system consists of a 10 nm IrMn$_3$ layer coupled to a 5 nm permalloy (Py) film. Longitudinal magneto-optical Kerr effect (MOKE), anisotropic magnetoresistance (AMR), and anomalous Nernst effect (ANE) measurements independently reveal the same unidirectional field shift of approximately 50 Oe, together with a consistent cosine angular dependence. The simultaneous observation of these signatures establishes a direct correspondence between the interfacial magnetic symmetry imposed by the non-collinear antiferromagnet and the responses of the adjacent ferromagnet. This symmetry is manifested consistently in magnetization reversal, charge transport, and thermally driven voltage generation, demonstrating that the exchange-bias imprint is not restricted to a single experimental observable. Our results reveal a coherent multifunctional response of IrMn$_3$/Py and extend the conventional understanding of exchange bias beyond collinear antiferromagnetic systems. More broadly, they demonstrate the potential of non-collinear antiferromagnets as platforms for coupling magnetic, electrical, and thermoelectric functionalities in spintronic and spin-caloritronic devices.
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All authors André José, Adrielson Dias, Carlos Eduardo, Giovanna Celly, Luiza Paffer, José Araújo, José Laurentino, Monalisa Cavalcante, José Holanda

Saturday 26 September

Optics

Vision-Language Agents for Active Perception in Optics Laboratories

Ryan Lopez, Sachin Vaidya, Seou Choi et al. (+2 more)

Vision-language models (VLMs) are increasingly being used in scientific workflows, but their ability as agents to directly control laboratory experiments from visual feedback remains underexplored. This capability is important because many laboratory tasks do not naturally provide dense, pre-defined numerical objectives: informative signals can be sparse, intermittent, or visually ambiguous. A more general laboratory agent should instead be able to interpret visual observations, take actions to acquire useful feedback, and adapt its behavior based on the consequences of those actions. We study whether general-purpose VLMs can perform this kind of closed-loop scientific control using experimental optics as a testbed. We evaluate agents on three experimental systems that isolate distinct capabilities: a Michelson interferometer, a two-mirror cavity, and a four-mirror optical relay. The agents observe camera images, directly issue actuator and measurement commands, and retain their interaction history without receiving an engineered scalar objective during control. Across these experiments and matched simulations, we find that, given task-specific natural-language guidance, VLMs can estimate actuator-response relationships, resolve ambiguous observations through intervention, and actively create informative visual feedback when signals are sparse. These results suggest that pretrained multimodal models can serve as important decision-making agents within the experimental loop. Our work also establishes optics as a physically grounded testbed for visual reasoning and active perception in scientific agents.
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All authors Ryan Lopez, Sachin Vaidya, Seou Choi, Serena Landers, Marin Soljačić

Optics

Reconfigurable Linear Optical Transformations in a Single Integrated Multimode Waveguide

Manoah van der Worp, Jonas Krimmer, Ivo M. Vellekoop et al. (+2 more)

Wavefront shaping enables control over optical fields for applications ranging from imaging to photonic information processing. While conventional wavefront shaping relies on free-space systems comprising bulk optical components, compact and fully integrated approaches are comparatively unexplored. Here, we introduce a concept based on a single multimode waveguide with distributed thermo-optic perturbations for controlling multimode propagation. We develop a differentiable physical model and numerically demonstrate shaping the outgoing wavefront and programmable linear optical transformations, using gradient-based optimization. We achieve diffraction-limited focusing with 20 spatial modes and show that the theoretical focusing limit can be retained while maintaining more than $99\%$ of the input optical power. We extend this approach to complete input–output transformations and implement Sylvester–Hadamard matrix operations with dimensions up to $32\times32$ with correlations exceeding $99\%$. Reducing the number of tunable elements requires stronger individual perturbations, resulting in stronger and broader mode coupling that extends beyond the target modes. To mitigate this effect, we consider ancillary modes and realize a $4\times4$ transformation that reaches $93.8\%\pm4.8\%$ correlation with only $5N^2$ tunable elements, where $N=4$ denotes the number of spatial modes. The best-performing realization reaches $98.3\%$ correlation with the target. Our results demonstrate that thermo-optic control of multimode waveguides offers an approach to fully-integrated wavefront shaping and programmable linear optical transformations, with potential applications in classical and quantum photonic processing
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All authors Manoah van der Worp, Jonas Krimmer, Ivo M. Vellekoop, Pepijn W. H. Pinkse, Stefan Rothe

Optics

Inverse-Designed Time-Varying Multilayers for Programmable Frequency-Momentum Light Scattering

Mohammad M. Asgari and Viktar Asadchy

Space-time-varying electromagnetic structures unlock wave-control mechanisms inaccessible to static media, including frequency conversion, harmonic generation, and joint control over frequency and momentum. Here, we introduce an inverse-design framework for multilayer space-time-periodic structures in which the spatial permittivity distribution and temporal modulation profile are optimized jointly. The proposed platform comprises multiple pixelated layers that are periodic along one or both transverse directions and harmonically modulated in time, enabling the direct synthesis of complex multichannel frequency-momentum scattering responses. We demonstrate two representative functionalities: independent control over the amplitudes and phases of three transmitted spatiotemporal channels and the generation of a frequency-momentum comb. Across these examples, we consider both continuous and binary permittivity distributions. To facilitate reproducibility and further development, we make the numerical implementation of the optimization framework freely available. These results demonstrate that inverse-designed time-varying multilayers provide a compact and versatile route toward programmable frequency-momentum multiplexing and the synthesis of space-time wave packets. The optimization code is made openly available to facilitate reproducibility and further development of the proposed inverse-design framework.
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Optics

Asymmetric Negative Refraction in Nonlocal Double-Wire Metamaterials

Tiago A. Morgado, Sylvain Lannebère, Enrico M. Renzi et al. (+2 more)

We demonstrate that heterogeneous double-wire metamaterials, comprising two dissimilar and nonconnected wire arrays, enable loss-asymmetric hyperbolic dispersion and strongly asymmetric negative refraction. We unveil that, owing to their strongly nonlocal response and distinctive microstructure, such geometry supports two independent hyperbolic propagation channels with unequal losses, which can be selectively excited by free-space propagating waves incident at opposite angles. This angular selectivity gives rise to asymmetric negative refraction at the air-metamaterial interfaces, characterized by strong angular asymmetry in transmission and absorption, while preserving reciprocity. This phenomenon is scalable and can be realized with metallic wire arrays over a broad frequency spectrum extending from microwave to infrared frequencies, showing that nonlocality can emulate shear-like dissipative asymmetry that, in local media, requires lower spatial symmetry. Our findings open new avenues for directional energy transport and angle-selective wave control in photonic platforms.
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All authors Tiago A. Morgado, Sylvain Lannebère, Enrico M. Renzi, Andrea Alù, Mário G. Silveirinha

Optics

Geometry-Controlled Polarization Photocurrents in Scalable PtSe2 Infrared Pixels

Eunice Y. Paik, Owen A. Vail, Madaline R. Marland et al. (+11 more)

Polarization-sensitive photodetectors provide multi-dimensional optical information beyond the capabilities of traditional intensity-based detectors. The noble metal dichalcogenide PtSe2 presents unique opportunities for tunable polarization detection due to its strong spin-orbit coupling, material stability, customizable broadband polarization responses, and direct compatibility with a wide range of substrates for back-end-of-line silicon integration. In this work, we demonstrate room-temperature near-infrared to mid-wavelength infrared polarization photoresponses using scalable, as-grown, wide-area PtSe2 films, and we show that the measured polarization response is reshaped by device geometry. Finite-element current-flow simulations reproduce the observed spatial redistribution of the polarization-sensitive response and localize the transverse polarization response near the pixel center. This geometry-enabled separation allows wavelength-dependent laser spot scans to distinguish symmetry-allowed photocurrents from contact-proximate, dichroism-mediated photothermal contributions. At near-infrared wavelengths, we observe spatial response that is consistent with linear-dichroic photothermoelectric currents, whereas mid-wavelength infrared measurements reveal a helicity-dependent photothermal contribution under oblique illumination. These results identify pixel boundary engineering as both a design lever and a diagnostic tool for scalable PtSe2 polarization-sensitive infrared pixels.
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All authors Eunice Y. Paik, Owen A. Vail, Madaline R. Marland, William A. Beck, Antonio Llopis-Jepsen, Wendy L. Sarney, Jeffery H. Leach, Stefan Heiserer, Nikolas Dominik, Cormac Ó Coileáin, Paul B. Seifert, Georg S. Duesberg, Blair C. Connelly, George J. de Coster

Friday 25 September

Optics · Cross-listed from physics.app-ph

A reduced-order analysis for multi-reflection-driven laser absorptance in vaporization-induced cavities

Haolin Liu, Haoran Shi, Xuzhe Zeng et al. (+4 more)

Multiple internal reflections enhance laser absorption in vaporization-induced cavities, but connecting ray histories, cavity geometry, and absorptance typically requires full ray tracing. We develop a reduced-order framework based on Beer-Lambert-type attenuation governed by an effective per-reflection optical depth (EPROD). A power-weighted formulation defines an absorptance-equivalent interaction count under constant effective single-interaction absorptance, while a cumulant expansion separates the EPROD-independent mean interaction count from ray-path heterogeneity corrections. Across nine simulation groups spanning three alloys and three spot diameters, the mean interaction count follows a unit-intercept linear depth relation with R-squared values of 0.7824-0.9843. Its slope varies by only 3.4%-6.3% across alloys at fixed spot diameter and decreases with increasing spot diameter. Fixing this slope from ray statistics yields an absorptance-depth model with one fitted parameter and a median prediction error (MAPE) of 2.61%. An independent synchronized Ti-64 experiment yields model parameters within approximately 2.4% of corresponding simulation values. This framework separates geometric interaction accumulation from optical attenuation, enabling efficient energy-coupling prediction and absorptance-based keyhole characterization.
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All authors Haolin Liu, Haoran Shi, Xuzhe Zeng, Brian J. Simonds, Wenda Tan, Anthony D. Rollett, Levent Burak Kara

Optics

Discrete quality-factor control in a side-coupled photonic crystal microcavity: evanescent Bloch tunnelling and the finite-cell correction

Hasan Oguz

A point-defect cavity side-coupled to a line-defect waveguide in a two-dimensional photonic crystal of silicon rods in water is studied with plane-wave expansion and finite-difference time-domain computations. The defect-rod radius tunes the resonance continuously within the band gap, as first-order perturbation theory predicts, whereas the quality factor changes in discrete steps set by the number of lattice rows between cavity and guide; displacing the defect rod by up to a tenth of a period changes it by less than 7 percent. Each added row multiplies the quality factor by a factor that follows, without an adjustable parameter, from the decay of the evanescent Bloch channel of the bulk crystal that is phase-matched to the guided mode; the channel at zero wavevector along the guide predicts little more than half that factor. Two biases of a finite computational domain, leakage across the cladding and a standing wave set up by reflections at the ends of the truncated guide, lower the per-row factor and change the quality factor by up to a factor of two if left uncorrected. Scaled to 1550 nm the design gives a sensitivity of 634 nm per refractive index unit, which perturbation theory reproduces, and the linewidth agrees with that of a transmission spectrum normalized to a cavity-free reference. Absorption by water caps the quality factor near 9200 and limits the useful number of barrier rows. The guided mode lies inside the light cone, so a slab of finite height needs a different guide.
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Optics · Cross-listed from physics.plasm-ph

Joint Amplitude-Phase Optimization of Broadband Lasers Raises Absolute Two-Plasmon-Decay Thresholds Above Coherence-Time Predictions

A. S. Joglekar, R. K. Follett, D. H. Froula et al. (+1 more)

Broadband lasers suppress the absolute two-plasmon-decay instability that preheats inertial-fusion targets. The usual scaling relates this suppression to the drive's coherence time, a power-spectrum statistic insensitive to spectral phase. By gradient descent through a differentiable enveloped wave solver, we show that at fixed power spectrum phase optimization raises the threshold from the random-phase median of $2.8\,I_\mathrm{mono}$ to $4.1\,I_\mathrm{mono}$, but produces a transform-limited (TL) pulse train with peak-to-average ratio $R=32$. Joint amplitude–phase optimization reaches $5.6\,I_\mathrm{mono}$ at $R=3.6$, above the best tested TL line-count result of $4.5\,I_\mathrm{mono}$ at $R=16$; relaxing the peak constraint raises the joint threshold to $6.4\,I_\mathrm{mono}$. An exact growth-rate budget evaluated inside the simulation separates the two mechanisms. TL suppresses coupling mainly by concentrating the pump field into short bursts, thereby lowering its time-averaged magnitude at fixed average intensity. The joint optima retain near-random values of this amplitude measure while suppressing both the available coupling and the fraction realized through pump–daughter alignment. The advantage of joint optimization persists from $1\%$ to $4\%$ bandwidth and from OMEGA-scale to ignition-scale conditions.
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All authors A. S. Joglekar, R. K. Follett, D. H. Froula, J. P. Palastro

Optics · Cross-listed from quant-ph

Exact series formulas for the capacities of the amplitude damping channel

Stefano Pirandola

We derive explicit, absolutely convergent series formulas for the quantum, unassisted classical, and entanglement-assisted classical capacities of the qubit amplitude damping channel, eliminating residual optimizations and implicit roots. We also obtain analytical upper and lower bounds on two-way assisted quantum and private communication capacities by evaluating a balanced-squashing bound and optimizing the reverse coherent information. Our results characterize the optimal input populations, establish convergence and truncation properties, and provide analytical benchmarks for quantum and classical communication over dissipative channels.
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Optics · Cross-listed from quant-ph

Scalable Hybrid Device Architecture on Thin-Film Lithium Tantalate for Long Distance Quantum Network Nodes with Atomic Frequency Comb Quantum Memories

Ayed Sayem and Towsif Taher

Scalable photonic circuits are essential for realizing practical quantum networks beyond proof-of-principle demonstrations. Although diamond-based integrated photonics has been extensively investigated over the past two decades for quantum networking applications, its integration into scalable photonic platforms remains challenging. Quantum memories based on rare-earth-ion atomic frequency combs (AFCs) offer an attractive alternative; however, most demonstrations to date have relied on bulk free-space crystals, limiting their scalability for practical implementations. In this work, we systematically investigate the potential for hybrid integration of AFC-based quantum memories with a scalable integrated photonic platform. We propose a device architecture combining thin-film lithium tantalate (TFLT) nanophotonic circuits with ytterbium-doped yttrium orthosilicate (Yb:YSO) crystals for long-distance quantum communication. Our analysis shows that the hybrid TFLT-YSO platform offers a promising and scalable pathway toward integrated quantum memories and, ultimately, large-scale quantum networks.
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Optics

A unified sensitivity kernel for coherent wave tomography in radar, seismic, ultrasound, and optical imaging

Alexey Yamilov

Imaging an inhomogeneous medium with waves rests on the sensitivity of a boundary measurement to a change inside. Radar, seismology, medical ultrasound, and diffuse optics cast this sensitivity as a kernel of area-specific form. Here we show that all of them are built from two classes. The classes stem from the complex material parameter of the underlying wave equation, its real part determining the wave speed and its imaginary part the loss. Every kernel is the product of a forward and an adjoint field, and a real measurement retains one quadrature of that product. These quadratures are the two classes, and all kernels in ballistic and diffusive transport are combinations of them. We place the areas on one diagram of scattering strength and transport depth, exposing a shared computational limit set by wavefield storage, and propose a broadband on-shell compression that can relax that limit.
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Optics · Cross-listed from cond-mat.mes-hall

Rydberg excitons in core-shell nanostructures II. Plasmon-exciton interaction and enhancement

David Ziemkiewicz, Gerard Czajkowski and Sylwia Zielińska-Raczyńska

Interaction between Rydberg excitons in core-shell Cu$_2$O nanostructures and surface plasmons is investigated. An enhancement of a quadrupole transitions to the Rydberg exciton states in copper oxide plasmonic nanaostructures is examined. A possibility of a modification of plasmonic enhancment (i.e., an average amplification factor) of electric field distributions in the vicinity of nanostructures, which depends on its shape and geometrical size, is also discussed.
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Optics

Direct Observation of Switching-Wave Dynamics in 20 GHz Normal Dispersion Spiral Microresonators

Van Doan Le, Julien Fatome and Erwan Lucas

Integrated Kerr frequency combs are powerful tools for microwave photonics, spectroscopy, and optical communications. While traditional architectures rely on the anomalous-dispersion regime, this typically requires thick, highly strained silicon nitride layers that complicate standard CMOS-foundry fabrication. Thinner layers circumvent these fabrication constraints but yield normal-dispersion microcombs that generally require specific trigger mechanisms, such as deterministic seeding, due to the absence of spontaneous modulational instability. Here, we demonstrate the generation of a 20 GHz microcomb in the normal-dispersion regime, driven by a synchronized dual-pump scheme via electro-optic sidebands modulation. The platform leverages an Archimedean spiral geometry on a foundry-compatible, 350 nm-thin SiN platform. By employing adiabatic curvature engineering, the resonator balances a compact footprint with an intrinsic quality factor exceeding $7 \times 10^6$, while effectively eliminating avoided mode crossings with higher order modes. This strong-dispersion architecture yields a low-repetition-rate microcomb featuring high power-per-line and picosecond-scale temporal profile, which enables the direct optical sampling and characterization of the out-coupled switching wave waveforms. The measured dynamics across a range of pump desynchronizations demonstrate excellent agreement with simulations. Our work establishes a scalable, strategy for footprint-efficient normal-dispersion microcomb generation at microwave frequencies, with potential for scaling to other wavelength ranges.
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Optics

High-Yield, 150 ps Polymer Scintillators via Synergistic Purcell and High-Z Enhancement

Xiaohe Zhou, Hiba H. Karakkal, Chenger Wang et al. (+12 more)

Developing plastic scintillators that simultaneously achieve high light yield (LY), ultrafast timing, and scalable processability remains a formidable challenge in radiation detection. Here, we report a solution-processable hybrid scintillator that integrates high-Z sensitization with Purcell-enhanced radiative recombination within a conjugated-polymer platform. By embedding HfO2 nanoparticles and resonant Ag-SiO2 plasmonic nanoantennas into a poly(9,9-dioctylfluorene) matrix, we exploit the intrinsic sub-nanosecond kinetics of conjugated polymers while overcoming their characteristic low stopping power. The HfO2 nanocrystals amplify energy deposition and suppress interchain aggregation, preserving high photoluminescence quantum yields in the solid state. Simultaneously, the nanoantennas induce strong plasmon-exciton coupling, accelerating radiative decay to ~150 ps. This synergistic architecture yields LY=6.1 photons/keV, comparable to standard commercial plastics with nanosecond lifetimes, yet over an order of magnitude higher than current sub-nanosecond state-of-the-art materials. This performance represents one of the most favourable combinations of efficiency and timing resolution reported to date. Our versatile strategy provides a framework for next-generation organic scintillators, merging record-breaking temporal response with high efficiency for advanced radiation-sensing architectures.
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All authors Xiaohe Zhou, Hiba H. Karakkal, Chenger Wang, Andrea Fratelli, Francesco Bruni, Matteo L. Zaffalon, Leonardo Poletti, Saptarshi Chakraborty, Emanuele Mazzola, Roberto Lorenzi, Francesco Carulli, Francesca Rossi, Francesco Meinardi, Luca Gironi, Sergio Brovelli

Optics

Probing the formation of femtosecond laser-induced periodic surface structures on silica films by ultrafast small-angle X-ray scattering

Dominik Kaczmarek, Jean-Luc Déziel, Thies Johannes Albert et al. (+16 more)

Ultrashort X-ray pulses, as provided by X-ray Free Electron Lasers (XFELs), offer unique opportunities to probe the formation of laser-induced nanostructures with sizes even below the optical diffraction limit, with sub-micometer and sub-picosecond spatial and temporal resolution. Using ultrafast small-angle X-ray scattering (SAXS), we probe the formation of nanoscatterers and nanocracks in reciprocal space as they evolve into different types of laser-induced periodic surface structures (LIPSS) on silica films. Our focus is on the dynamics and evolution of nanoscatterers and high spatial frequency LIPSS (HSFL), with spatial periods below 100 nm. Our experiments include an in-situ analysis of the pulse-by-pulse evolution of HSFL at a fixed sample location, as well as fs time-resolved delay and fluence scans using an ultrafast pump-probe scheme. We find that nanoscatterers and periodic nanocracks form at delay times of hundreds of picoseconds and subsequently evolve into HSFL. At low laser fluences, inter-pulse incubation effects become important during multi-pulse irradiation. Simultaneously, inter-pulse feedback leads to an ordering and improve the regularity of the HSFL. The experiments are complemented by theoretical analyses, including numerical Finite-Difference Time-Domain (FDTD) simulations. These combined analyses allow us to propose a five-stage model of LIPSS formation on silica films upon irradiation with fs-laser pulses.
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All authors Dominik Kaczmarek, Jean-Luc Déziel, Thies Johannes Albert, Matthias Weise, Jerzy Antonowicz, Robert Carley, Devesh Chopra, Loïc Le Guyader, Laurent Mercadier, Giuseppe Mercurio, Roman Minikayev, Mianzhen Mo, Andreas Scherz, Ryszard Sobierajski, Yanwen Sun, Martin Teichmann, Peter Zalden, Klaus Sokolowski-Tinten, Jörn Bonse

Optics · Cross-listed from quant-ph

Optical characterization of excited-state spin Hamiltonians and clock transitions at telecommunication wavelength in Tm3+:YAlO3

Akshay Babu Karyath, Luozhen Li, Julien Bertrand et al. (+6 more)

The zero-phonon line (ZPL) between the two excited-state manifolds 3F4 and 3H4 of the trivalent thulium ion in yttrium aluminum perovskite (Tm3+:YAlO3) lies within the telecom E-band at around 1451 nm and exhibits an optical coherence time of a few {\mu}s at cryogenic temperatures. To improve this time in view of potential applications, e.g. single-photon sources and optical quantum memory, we characterized the magnetic properties of the lowest Stark levels of these two manifolds. Varying the external magnetic field amplitude and orientation, we measured the enhanced nuclear Zeeman splitting by probing the field-dependent frequency detuning of side holes created by means of spectral hole burning, and we characterized the inhomogeneous line shift caused by the quadratic Zeeman interaction. Together, this allowed us to establish the spin Hamiltonians for the lowest Stark level of the 3F4 and 3H4 manifolds, and to predict optical clock transitions for particular orientations and magnitudes of the magnetic field
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All authors Akshay Babu Karyath, Luozhen Li, Julien Bertrand, Alexandre Kings, Tianyang Shen, Gabriel Aeppli, Simon Gerber, Guy Matmon, Wolfgang Tittel

Optics

Probing temperature dependent non-radiative decay channels in CrSBr with nonlinear optics

Minjiang Dan, Till Weickhardt, Paul Herrmann et al. (+9 more)

Among the recently discovered layered magnetic materials, the antiferromagnet CrSBr has attracted considerable interest thanks to its stability, quasi-one-dimensional crystal structure, and direct near-infrared band gap. These properties make it a suitable platform for combined electrical, magnetic, and optical measurements, and thus for studying exciton dynamics and transport across different magnetic phases. In this work, we investigate the optical response of CrSBr across its paramagnetic and antiferromagnetic phases by combining nonlinear optical spectroscopy, including second-harmonic generation, third-harmonic generation, and two-photon photoluminescence, with linear photoluminescence measurements. The observation of a clear difference in the temperature dependence of third-harmonic generation and photoluminescence intensities allows us to identify the onset of non-radiative recombination channels in the antiferromagnetic phase.
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All authors Minjiang Dan, Till Weickhardt, Paul Herrmann, Fabian Glatz, Marie-Christin Heißenbüttel, Thorsten Deilmann, Michael Rohlfing, Ksenia Mosina, Zdeněk Sofer, Benjamin Pingault, Julian Klein, Giancarlo Soavi

Optics

High-gain vortex transfer via activated forbidden transitions in molecular magnets

Fan Meng, Hao Zhu, Xin-Yao Huang et al. (+1 more)

Vortex light has garnered considerable interest in recent years owing to its distinctive properties and broad application potential. In this paper, we employ a conventional three-level ladder-type configuration in molecular magnets to realize high-gain vortex light transfer by enabling otherwise forbidden transitions. We demonstrate that the intensity and phase of the generated vortex signal field are governed by the detuning of the probe field and the strength of the control field, and that the topological charges of the incident and generated fields obey a well-defined algebraic relation during the vortex transfer process. Furthermore, we show that, in molecular magnets, the Autler-Townes splitting (ATS) effect yields a larger vortex signal field gain than electromagnetically induced transparency (EIT) over a broad parameter range in nonlinear three-wave mixing. This result suggests that the widely accepted view of EIT as the dominant enhancer of nonlinear optical effects may not hold universally. In addition, we revisit previous studies and re-examine the characterization of vortex beam transfer efficiency, emphasizing the need for a more careful interpretation in multi-beam interaction systems. Leveraging the long spin coherence and microwave transitions of molecular magnets, our results may enable quantum information transfer, storage, computing, and radar imaging in solid-state platforms.
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All authors Fan Meng, Hao Zhu, Xin-Yao Huang, Guo-Feng Zhang

Optics

Distributed laser energy deposition enables fog-resilient optical communications

Malte C. Schroeder, Victor Moreno, Christophe Coreixas et al. (+2 more)

Fog and clouds remain major obstacles to free-space optical (FSO) communications because micron-sized droplets can impose tens of decibels of attenuation. Ultrashort laser filamentation can transiently clear fog in laboratory-scale experiments, but its extension to atmospheric-scale propagation has remained uncertain. Here we demonstrate laser-assisted fog clearing under atmospheric-scale propagation conditions over a 140-m optical path using a high-energy, high-average-power picosecond laser and weak focusing to sustain extended multifilamentation. A steady-state transparent channel approximately 2 cm in diameter restores up to 12 dB of transmission for an independent optical beam. Increasing the clearing-laser pulse energy primarily extends the multifilament region while maintaining a nearly constant longitudinally averaged deposited energy per unit length of ~2 mJ/m over the measured bundle length. This low average deposition, together with self-sustained filament propagation through dense fog, provides a favorable scaling route toward weather-resilient optical links.
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All authors Malte C. Schroeder, Victor Moreno, Christophe Coreixas, Jonas Latt, Jean-Pierre Wolf

Optics

From OpenSPIM to FlowSPIM: Enhancing the versatility of a light sheet microscope through an iterative design process

Endre Joachim Lerheim Mossige, Sergey Ponomartsev, Natalia Smirnova et al. (+12 more)

Light sheet microscopy is ideal for the 3D imaging of large biological specimens, yet systematic documentation on adapting microscope designs to diverse experimental requirements remains limited. We present the iterative process used to design and build a modular light-sheet microscope and adapt it to different sample types and experimental conditions. Starting from a stripped-down OpenSPIM platform, we gradually make our microscope more versatile by implementing new hardware, such as additional laser channels and optical filters, and new protocols for sample handling. In its final iteration, FlowSPIM is a new flow-based incubation technique for 3D tissue culture.
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All authors Endre Joachim Lerheim Mossige, Sergey Ponomartsev, Natalia Smirnova, Wietske van der Ent, Siri Andresen, Xian Hu, Felix Margadant, Rainer Heintzmann, Roland Kádár, Kesavan Sekar, Helene Knævelsrud, Camila Vicencio Esguerra, Stefan Krauss, Dag Kristian Dysthe, Alexander Refsum Jensenius