Optics · Cross-listed from quant-ph
Quantum magnonics with engineered dissipative and coherent interactions
Debsuvra Mukhopadhyay, Jayakrishnan M. P. Nair and Girish S. Agarwal
Cavity magnonics is moving beyond the conventional paradigm of coherent
spin–
photon hybridization toward the controlled engineering of dissipative and coherent interactions, Floquet dynamics, and
quantum fluctuations. This Perspective examines how these ingredients reshape collective dynamics and open new avenues for
quantum state engineering, transport, and sensing. We discuss the role of dissipative coupling and anti-$\mathcal{PT}$
symmetry in enabling long-lived collective modes and enhanced spectral response, and highlight Floquet engineering as a means of engineering nonreciprocal transport and phase-controlled interactions. We then review recent progress in
quantum magnonics, ranging from squeezed and entangled
magnon states, including the squeezing of thermal
magnons, to prospective schemes for preparing magnonic Schrödinger-cat states. We also discuss how parametric driving and active gain strongly modify hybrid susceptibilities and amplify
magnon–
photon response. These advances expand the scope of cavity magnonics beyond conventional polariton physics, establishing it as a versatile platform for sensing, transduction,
spin transport, and hybrid
quantum technologies.
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Optics
Beam angle-locked loop in laser interferometry
Daikang Wei, Christoph Bode, Vitali Müller et al. (+2 more)
Maintaining precise beam coalignment is essential in
laser interferometry, particularly for interspacecraft missions where angular misalignments introduce tilt-to-length coupling noise and risk complete link failure. This work presents a comprehensive theoretical and experimental framework for the beam angle-locked loop, which maintains coalignment between two interfering beams. Minute angular misalignments are detected via differential wavefront-sensing signals, which are used as the error signal for feedback control. A detailed linear control model incorporating an angle detector, a digital filter, a proportional-integral-double-integral servo, a digital-to-analog converter, and a beam-steering mechanism is developed. Using loop transfer functions, we establish a noise-propagation model that quantifies the contributions of individual components to both out-of-loop and in-loop angle errors. The analytical results are experimentally validated using a transponder-based interferometric link spanning two optical benches, with a hexapod simulating spacecraft attitude jitter. The measured transfer functions and coalignment performance agree well with theoretical predictions, yielding a pointing stability better than 10 urad$/\sqrt{\text{Hz}}$ between 0.2 mHz and 1 Hz. Furthermore, a loop-optimization strategy is demonstrated to minimize angle misalignment within a target frequency band by tuning the servo gain, without requiring hardware modifications. This validated framework provides a reliable architecture for designing and optimizing active beam
alignment in
laser interferometry.
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All authors Daikang Wei, Christoph Bode, Vitali Müller, Juan José Esteban Delgado, Gerhard Heinzel
Optics · Cross-listed from cond-mat.quant-gas
Limit Cycles in a Photonic Dimer with Tuneable Non-Hermitian Interactions
Kevin J. H. Peters, Peter Schnorrenberg, Daniel Ehrmanntraut et al. (+2 more)
Interactions govern the emergence of collective behaviour in classical and
quantum many-body systems. While conservative interactions are well known to generate nonlinear phenomena ranging from self-trapping to pattern formation, it remains largely unexplored whether purely dissipative – i.e., non-Hermitian – interactions can give rise to similarly rich dynamics and nontrivial system states. Here, we experimentally realise tuneable non-Hermitian interactions in two coupled condensates of light confined within a dye-filled double-well microcavity. Local coupling to molecular reservoirs generates the effective dissipative
photon interactions. We show that the interplay between coherent tunnelling and interactions stabilises limit-cycle oscillations, a hallmark of nonlinear dynamics traditionally associated with Hermitian nonlinearities. By tuning the reservoir coupling, we map out the dynamical phase diagram comprising stable fixed points and limit cycles, thereby demonstrating direct control over the interaction strength. Our experimentally validated model reveals both supercritical and subcritical Hopf bifurcations, giving rise to hysteresis, bistability and excitability. These results validate dissipative interactions as a mechanism for organising collective nonlinear dynamics in driven-dissipative systems and pave the way towards exploring nonequilibrium many-body physics through controlled dissipation.
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All authors Kevin J. H. Peters, Peter Schnorrenberg, Daniel Ehrmanntraut, Nikolas Longen, Julian Schmitt
Optics
Spectro-temporal shaping of broadband optical wavepackets via programmable on-chip photonics
Bruno P. Chaves, Jérémy Saucourt, Van Thuy Hoang et al. (+9 more)
The ability to precisely shape the properties of light over multiple degrees of freedom constitutes the foundation of modern photonic architectures. Broadband sources with addressable spectro-temporal content are for instance critical for applications spanning biomedical imaging, material processing,
lidar, and ultrafast spectroscopy, but also key enabling technologies in
quantum information processing, high-capacity communications, and optical computing. Yet, flexible and adjustable spectro-temporal shaping so far remains a significant challenge, as it requires the simultaneous manipulation of both frequency and temporal domains across broad spectral bandwidths and extended timescales, from femtoseconds to nanoseconds. Importantly, conventional approaches to spectro-temporal processing typically rely on bulky and complex optical systems that lack scalability and flexibility, ultimately hampering their utility for applications requiring addressable multiphotonic processes. Here, we present a framework for spectro-temporal wavepacket control over a broad bandwidth, merging programmable integrated photonics with high-speed optical characterization. Leveraging machine leaning for tailoring nonlinear pulse propagation, we experimentally report scalable and on-demand shaping of broadband ultrafast pulse patterns. We demonstrate the efficacy of our method through reconfigurable power across 400 nm bandwidth with picosecond resolution, with promises for applications where precise control over light is paramount, in particular those needing versatile and controllable multiphoton excitations.
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All authors Bruno P. Chaves, Jérémy Saucourt, Van Thuy Hoang, Alexis Bougaud, Yassin Boussafa, Erwan Ferrandon, Sai T. Chu, Brent E. Little, David J. Moss, Roberto Morandotti, Vincent Couderc, Benjamin Wetzel
Optics
Non-Hermitian reconstruction of hybridized hyperbolic shear polaritons
Zijia Dang, Zhe Cui, Gang Zhong et al. (+2 more)
Hyperbolic shear polaritons (HShPs) represent a distinctive class of anisotropic polaritonic states that enable directional subwavelength light manipulation through asymmetric momentum-space dispersion, while their control in twisted systems has so far relied mainly on
geometric and spectral parameters. Here, we introduce non-Hermitian dissipation as an additional degree of freedom for tuning HShPs in twisted van der Waals
heterostructures. In twisted {\alpha}-MoO3/{\alpha}-V2O5
heterostructures with closely matched isofrequency contours but distinct dielectric losses, dissipation modifies the complex hybrid polaritonic states and thereby tunes the resulting momentum-space and real-space asymmetry. Near-field infrared imaging combined with analytical modeling and full-wave simulations reveals the
evolution of the shear response with twist angle, excitation frequency, layer thickness, and substrate dielectric environment. The interplay between material dissipation and dielectric screening enables continuous regulation of the shear degree and reversible switching between shear-off and shear-on states. Furthermore, we demonstrate a proof-of-concept binary-state encoding scheme based on dissipation-controlled shear-state switching. Our work identifies non-Hermitian dissipation as an additional control parameter in twisted polaritonic systems, expanding the available design space for reconfigurable mid-infrared nanophotonics.
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All authors Zijia Dang, Zhe Cui, Gang Zhong, Jingying Liu, Qingdong Ou
Optics
A 0.35 mm Silicon Carbide Diffractive Waveguide with Dual Parameter Apodization for Full Color Augmented Reality
Xiaoxuan Li, Ce Li, Yinggang Chen et al. (+5 more)
Augmented reality eyewear offers a transformative interface poised to reshape human information interaction. In this context, silicon carbide (SiC) offers unique advantages for diffractive waveguides with its high refractive index and excellent thermal conductivity. However, in single-layer full-color displays, existing SiC waveguides generally remain thicker than 0.5 mm to reduce the bounce count of total internal reflection, thereby avoiding severe spatial variations in luminance and color. Here, we demonstrate a 0.35 mm SiC diffractive waveguide with an ultra-lightweight of only 1.98 g. The challenge of spatial non-uniformity is addressed by dual-parameter apodized gratings with continuously varying depth and duty cycle, enabling fine spatial control over local diffraction efficiency. To realize high-throughput production, a parallel gradient transfer method compatible with nanoimprint lithography is introduced, enabling wafer-scale patterning of four lens pairs per 8-inch SiC wafer. Furthermore, magnesium fluoride planarization suppresses grating visibility and achieves a high see-through transmittance of 92%. Optical simulations confirm that this architecture achieves balanced full-color transmission across a 30-degree field of view. This strategy provides a scalable route toward ultra-light and visually unobtrusive glasses, opening new opportunities for practical consumer-grade wearable displays.
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All authors Xiaoxuan Li, Ce Li, Yinggang Chen, Chenting Fang, Boqu Chen, Lu Cai, Kaikai Du, Min Qiu
Optics · Cross-listed from quant-ph
Analog-to-digital conversion in the quantum regime
Thomas Pousset, Matteo Schiavon, Guillaume Ricard et al. (+3 more)
Digital signal processing has become essential in
quantum optics, particularly for continuous-variable (CV) information encoding, enabling coherent detection schemes and mitigation of linear impairments. While linear signal processing in double homodyne detection has been studied under the assumption that all post-measurement processing can be backpropagated in the optical domain, a rigorous treatment of the digitization chain, spanning optical, electronic, and sampling stages, is still lacking. In this work, we consider the continuous mode description of double homodyne detection to fully capture the maximum mode-matching coefficient achievable as a function of electronic noise, signal bandwidth, receiver electronics bandwidth, and sampling rate, that is the entry point of digital signal processing. We establish a dimensioning rule that generalizes the Nyquist-Shannon criterion to account for
quantum fluctuations of the measured signal, not merely its bandwidth. Analyzing the case of additive white electronic noise, we find numerically that optimal signal-to-noise ratio is achieved when the electronic bandwidth is large enough to pass the signal yet narrower than the sampling rate in order to mitigate noise amplification, yielding a concrete design criterion for coherent detection.
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All authors Thomas Pousset, Matteo Schiavon, Guillaume Ricard, Elie Awwad, Romain Alléaume, Nicolas Fabre
Optics
Nonlinear dynamics of intra-cavity-field for periodically pump-modulated dual-coupled Kerr micro-ring cavities
Yiyi Zhang and Chaoying Zhao
We numerically investigate the long-time intra-cavity-field dynamics of a periodically pump- modulated pair of coherently coupled Kerr micro-ring resonators. Along a detuning scanning, fixed-phase stroboscopic trajectories change from recurrent regular state to states with positive maximum-Lyapunov growth. Long observation windows near the transition, where finite-time estimates converge slowly. The low- and high-detuning states both retain multi-mode Kerr-comb spectra, while their cycle-to-cycle field organization changes much more strongly. Spatiotemporal intensities, adjacent-cycle profiles, and full-field recurrence measures show a loss of one-period recurrence together with changes in the inter-resonator phase relation, coherent exchange, and dispersive intensity flow. We linearize the coupled equations around the long-time field and examine the growth of an infinitesimal perturbation. The resulting tangent-energy balance shows that the loss contribution changes little along the scanning, whereas the Kerr contribution increases and exceeds the loss magnitude in the high-detuning states with positive Lyapunov growth. A separate dimensional correspondence relates the normalized working range to Si3N4 micro-ring. These results provide a field-resolved description of the long-time dynamical change and its associated perturbation growth.
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Optics
Reduction of hydroxyl groups in optical nanofibers via in-fiber laser heating
Koki Oguri, Ken-ichi Harada, Samuel K. Ruddell et al. (+2 more)
Optical nanofibers fabricated using a standard oxyhydrogen flame exhibit optical losses at wavelengths around 1385~nm due to absorption by embedded hydroxyl groups, posing a challenge for the realization of
quantum electrodynamics systems using ytterbium atoms. Here, we establish a method for the reduction of hydroxyl groups by heating them with a
laser guided within the optical nanofiber under
vacuum conditions. The temperature of the optical nanofiber during heating is estimated by monitoring the phase shift of the transmitted light using an interferometer. As a result, evidence suggesting that hydroxyl groups were desorbed by
laser heating was obtained.
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All authors Koki Oguri, Ken-ichi Harada, Samuel K. Ruddell, Karen E. Webb, Takao Aoki
Optics · Cross-listed from cond-mat.mtrl-sci
Quantifying thermal and driven magnon populations with femtosecond noise correlation spectroscopy
F. S. Herbst, M. A. Weiss, A. Leitenstorfer et al. (+5 more)
Precise knowledge of the total number of
magnons, including both coherent and incoherent (e.g. thermal) excitations, is imperative for the advancement of fundamental
spin-wave physics and the development of next-generation magnonic devices. In particular, quantifying
magnons is key to understanding
magnon transport phenomena, the nonlinear regime, or ultrafast magnetization dynamics. Typically, incoherent
magnons are accessed by frequency-domain techniques, which lack the temporal resolution required for ultrafast processes, while ultrafast time-domain methods are generally sensitive only to the coherent dynamics. In this work, we demonstrate that femtosecond noise correlation spectroscopy enables a fully quantitative, time-domain measurement of both thermal and coherently excited
magnon modes in bismuth-substituted yttrium iron garnet driven by a free-running microwave. We model the experimental data and extract the
magnon number by simulating the
magnon band structure of the sample, the magneto-optical response function, and the optical spot size used in the experiment. Our analysis establishes a connection between
magnon mode calculations and experimentally accessible
magnetic properties and fiducially reproduces the waveform and amplitude of the magneto-optical correlation signal for different experimental conditions. These results open a new pathway towards the optical
tomography of
magnon modes in non-linear or non-
equilibrium conditions and can be readily extended to study ultrafast incoherent dynamics in other condensed matter systems.
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All authors F. S. Herbst, M. A. Weiss, A. Leitenstorfer, M. Lammel, N. Beaulieu, J. Ben Youssef, R. Schlitz, S. T. B. Goennenwein
Optics · Cross-listed from cs.NE
Photonic reservoir computing with dimensionally compressed readout
Gerald Kobi, Mohab Abdalla, Miguel C. Soriano et al. (+1 more)
This work addresses a hardware constraint in reservoir computing: the limited size of the readout layer imposed by systems with a physical readout. We investigate a strategy to accommodate this constraint based on random projection, which compresses high-dimensional reservoir states into a lower-dimensional subspace while preserving key properties of the source space and information- processing capabilities. To evaluate this approach, we compare a small, standalone time delay reservoir against a larger configuration whose output is projected down to match the same restricted readout dimension. Using task-independent metrics, we demonstrate that the distribution of information-processing capacities may differ between the two configurations, even at identical readout sizes. Furthermore, we perform a comprehensive hyperparameter scan to assess how both systems behave under varying physical regimes. Finally, we
benchmark this approach on the standard NARMA10 task, showing that the random projection framework can yield superior performance compared to a standalone constrained reservoir, within specific compression range. These results provide a scalable pathway to bypass physical readout bottlenecks in hardware-based reservoir computing.
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All authors Gerald Kobi, Mohab Abdalla, Miguel C. Soriano, Damien Rontani
Optics
Mechanical quality factor estimation from a nonlinear optical cavity response
Zohran Ali, Davide Tomasella, Daniel Allepuz Requena et al. (+2 more)
Intrinsic damping rate and quality factor ($Q$) are key parameters in optomechanical systems. However, in high-Q devices, their measurement is often challenging because probe-induced dynamical backaction (DBA) and the need to resolve and accurately track the mechanical resonance limit the performance of state-of-the-art techniques. Here, we introduce an all-optical ringdown method in the unresolved-sideband regime that exploits the nonlinear, time-averaged optical response induced by strong mechanical motion. We derive an analytical model of the time-averaged optical cavity response probed by a weak frequency-scanning
laser. During the
evolution of the mechanical oscillator, the excited motion modulates the Lorentzian lineshape into a double-horned profile whose peak separation enables an accurate estimation of the modulation amplitude. Tracking this response during the mechanical ringdown allows the intrinsic damping rate to be determined without resolving the mechanical oscillation. We apply the method to a density-modulated phononic
crystal membrane placed inside a high-finesse cavity and obtain mechanical quality factors consistent with independent measurements on the same platform. Our method requires a minimal optical setup, while offering an in situ diagnostic and reduced impact from probe-induced DBA and robustness against measurement noise. Finally, the model can describe other resonant systems dispersively coupled to coherent frequency modulations, providing new insights and measurement strategies that expand beyond the optomechanical platform.
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All authors Zohran Ali, Davide Tomasella, Daniel Allepuz Requena, Alexander Huck, Ulrik Lund Andersen
Optics · Cross-listed from quant-ph
Phase estimation in spontaneous nonlinear interferometry for enhanced quantum imaging
Jonas L. Moos, Cristofero Oglialoro, Enno Giese et al. (+1 more)
Bicolor
quantum imaging can reach, in principle, phase supersensitivity approaching the Heisenberg limit using squeezed light from high-gain parametric down-conversion, but established
quantum-imaging setups typically operate in the low-gain, spontaneous regime, where such scaling is inaccessible. Here, we show experimentally and theoretically that a symmetric nonlinear interferometer, even in the spontaneous regime, retains a phase-sensitivity advantage over configurations where
entanglement is not exploited as a
quantum-metrological resource, although the achievable phase sensitivity remains shot-noise-limited. This advantage appears as a shift of the optimal working point toward the dark fringe, the low-gain signature of the mechanism underlying high-gain supersensitivity. We derive design choices for phase-optimized nonlinear interferometers accordingly, favoring configurations that exploit
entanglement as a metrological resource and specifying their optimal operating point.
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All authors Jonas L. Moos, Cristofero Oglialoro, Enno Giese, Markus Gräfe
Optics
Planar metal-semiconductor Yagi-Uda type antennas for tunable narrow-linewidth quantum dot emitters
Ievgen Brytavskyi, Andreas Kitzmüller, Santanu Manna et al. (+13 more)
Tunable photonic architectures that improve the extraction efficiency of light from embedded epitaxial
quantum dots across a wide spectral range are key enablers for developing bright sources of single and indistinguishable
photons. In this study, we experimentally demonstrate planar multilayer
antenna structures consisting of epitaxially grown AlGaAs and InGaAs membranes containing
quantum dots sandwiched between metallic Au (or Ag) reflector and director layers together with Al$_2$O$_3$ spacer layers. We show that the linewidths and fine-structure splitting of the neutral
exciton emission remain comparable to those measured in the corresponding unprocessed samples, demonstrating that the fabrication process preserves the optical quality of the emitters. In addition to broadband operation, we demonstrate that the planar architecture is compatible with electrical tuning via integrated diode structures, and strain tuning using piezoelectric actuators. In spite of limitations related to optical losses in the ultrathin metallic layers, the demonstrated fabrication simplicity, scalability, and compatibility with tunable
quantum emitters establish planar
antennas as a promising platform for solid-state
quantum photonic devices.
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All authors Ievgen Brytavskyi, Andreas Kitzmüller, Santanu Manna, Gabriel Undeutsch, Christian Weidinger, Thomas Oberleitner, Ailton J. Garcia, Jr., Saimon Filipe Covre da Silva, Josef Resl, Raphael Joos, Robert Sittig, Michael Jetter, Simone L. Portalupi, Peter Michler, Armando Rastelli
Optics · Cross-listed from quant-ph
Momentum-Space-Engineered Spatial Photonic Ising Machine for Long-Range Interactions
Haijun Zhou, Hengyang Li, Maolin Wang et al. (+4 more)
Long-range Ising models (LRIMs) with dense nonlocal and competing interactions are central to statistical physics,
quantum simulation, and complex networks. Although the spatial photonic Ising machine (SPIM) exploits intrinsic optical parallelism for Ising computation, its ability to faithfully encode dense long-range couplings and capture the resulting thermodynamic signatures remains underexplored. Here, we present a momentum-space-engineered SPIM framework that maps prescribed long-range coupling kernels onto momentum-space masks for parallel
Hamiltonian evaluation. Based on a high-fidelity optical field propagation model, the annealing dynamics of LRIMs with power-law and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions are systematically investigated. For the power-law model, we investigate the modulation of the estimated critical temperature by the decay exponent {\sigma} and coupling cutoff radius R. For the RKKY model, we reproduce diverse ordered states induced by complex competing long-range interactions. A proof-of-principle experiment demonstrates the physical feasibility of our approach. This framework broadens the class of many-body systems accessible to the SPIM platform.
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All authors Haijun Zhou, Hengyang Li, Maolin Wang, Yunru Chen, Yingxiong Qin, Xiahui Tang, Gang Xu
Optics
Controllable ultrabroadband supercontinuum during twocolor femtosecond laser filamentation in high pressure gases
Yury E. Geints, Victor O. Kompanets and Sergey V. Chekalin
Twocolor
laser filamentation is considered a promising strategy for deep transformations of the spectrum and generating ultrashort light pulses, which is critically important for developing effective methods to control broadband coherent radiation in attosecond physics and ultrafast spectroscopy. We present the results of our experiments on the study of the spectral dynamics of supercontinuum generated during collinear twocolor filamentation of femtosecond pulses at the fundamental (800 nm) and second harmonic (400 nm) frequencies in Ar, N2, and CO2 gases at pressures up to 11 atm. We demonstrate that the transition to multiple filamentation in high pressure gases qualitatively changes the interaction dynamics between the color components. We demonstrate that instead of a simple merging of spectra broadened during filamentation, a complex, nonmonotonic dependence of the shape of the twocolor supercontinuum on the time delay between pulses is observed, including selective suppression of radiation in the 400 nm region. For the first time, significant differences are identified between the dynamics of twocolor filamentation in atomic and molecular gases. Particularly, in CO2, spectral transformation is preserved at picosecond interpulse delays, which is explained by the strong contribution of molecular rotational wave packets to the effective nonlinear polarizability. Our results demonstrate the possibility of controlled redistribution of spectral energy and dynamic switching off of individual regions of supercontinuum in atomic and molecular gases as their pressure changes, which fills the gap in understanding the spatiotemporal
evolution of multiple two color filaments and paves the way for the controlled formation of ultrashort
laser pulses.
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Optics · Cross-listed from cond-mat.mtrl-sci
Excitons probe intrinsic flat band Mottness in a van der Waals heterostructure
Xinyue Huang, Xintong Tan, Haowei Chen et al. (+12 more)
Excitons provide a sensitive optical probe of electronic correlations in nearby two-dimensional materials, yet their coupling to intrinsic flat-band Mott systems remains largely unexplored. Here we combine gate-tunable optical spectroscopy with first-principles calculations to study monolayer WSe$_2$ in direct contact with the van der Waals Mott
insulator Nb$_3$Cl$_8$. The gate
evolution of WSe$_2$ excitonic resonances reveals signatures of a correlation-reconstructed Mott gap in Nb$_3$Cl$_8$ that is absent from the single-particle band picture. In the electron-doped regime, the WSe$_2$ 2s Rydberg
exciton undergoes a multistage
evolution and develops into interlayer attractive and repulsive polaron branches, showing that a Rydberg
exciton can be dressed by strongly correlated flat-band electrons in an adjacent Mott layer. Under an out-of-plane
magnetic field,
spin-polarized Nb$_3$Cl$_8$ states further induce valley-selective
exciton coupling, producing a strongly enhanced circular polarization of the WSe$_2$
exciton emission. These results extend
exciton-based sensing and
exciton-polaron physics to intrinsic flat-band Mott materials, providing an optical route to probe and engineer correlation-driven interfacial quasiparticles.
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All authors Xinyue Huang, Xintong Tan, Haowei Chen, Yingzhou Huang, Yushen Zhou, Yuchen Gao, Zhijie Ma, Chengxin Xiao, Kenji Watanabe, Takashi Taniguchi, Jianpeng Liu, Zuxin Chen, Youguo Shi, Wang Yao, Yu Ye
Optics
Broad-angle photon-pair generation from flatband quasi-BIC resonant 3R-MoS$_{2}$ metasurfaces
Tingting Liu, Huifu Qiu, Xintong Shi et al. (+2 more)
Spontaneous parametric down-conversion (SPDC) in ultrathin optical resonant metasurfaces offers a promising platform for integrated
quantum light sources. However, conventional resonances suffer from steep momentum dispersion, limiting
photon-pair generation to narrow excitation and emission angles. Here, we demonstrate a flatband-resonant 3R-MoS$_{2}$ metasurface for high-efficiency, broad-angle SPDC
photon-pair generation. By implementing a supercell
symmetry-breaking strategy via Brillouin zone folding, we achieve a flatband quasi-bound states in the continuum (quasi-BICs) resonance in the near-infrared regime that maintains a robust quality factor across a wide range of incident angle. Exploiting the strong local electric field enhancement of resonance and the large second-order susceptibility of 3R-MoS$_{2}$, the metasurface boosts the degenerate SPDC pair-generation rate with orders of magnitude enhancement over an unpatterned film of identical thickness. Crucially, the near-zero band dispersion extends the effective emission angle to $\pm 5^{\circ}$ with negligible spectral drift $\sim 0.1$ nm and high directional tolerance. Under pulsed excitation with a finite spectral bandwidth, the
photon pair yield remains high, demonstrating strong spectral locking to the quasi-BIC resonance against pump detunings. This work establishes a versatile strategy for momentum-independent
quantum light sources, opening new avenues for scan-free
quantum ghost imaging and spatial-frequency
quantum processing.
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All authors Tingting Liu, Huifu Qiu, Xintong Shi, Jumin Qiu, Shuyuan Xiao
Optics
Modeling of jitter correction methods for asynchronous optical sampling
Mayuri Nakagawa, Natsuki Kanda and Ryusuke Matsunaga
Timing jitter management is crucial in asynchronous optical sampling (ASOPS) and dual-comb spectroscopy to maintain spectral bandwidth and fidelity. However, a quantitative framework predicting jitter correction efficiency from
laser phase noise has been lacking. Here, we present formulation and simulation models that evaluate jitter-suppression dynamics based on phase noise spectra. Our model quantifies the contrast between conventional triggering and software-based jitter correction. It also enables
retrieval of a jitter-free spectrum by compensating for jitter-induced power degradation. This work provides a universal design framework for optimizing diverse ASOPS systems by predicting residual jitter prior to system construction.
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Optics · Cross-listed from math.QA
Operator Michelson Contrast: Logarithmic Parametrisation, Subadditivity, and a Sharp Noncommutativity Threshold
Irina Nikolaeva and Andrej Novikov
We study the operator Michelson contrast Delta(A) = (kappa(A)-1)/(kappa(A)+1), with kappa(A)=||A|| ||A^{-1}||, for positive invertible operators, and introduce its logarithmic parametrization via arctanh(Delta(A)) = (1/2) ln kappa(A). This defines the Operator Logarithmic Contrast (OLC), extended to all invertible operators via polar decomposition. We prove OLC is subadditive under multiplication: OLC(AB) <= OLC(A)+OLC(B). For positive invertible A, we identify OLC(A) exactly as the projective Thompson distance from the identity ray to the ray of A. We establish a sharp dimensional threshold for equality in subadditivity: for dimensions 2 and 3, equality forces commutativity, while n=4 is the smallest dimension admitting noncommuting equality examples. Moreover, equality still forces commutativity in any total dimension if the operators factor as pure Kronecker products X = tensor X_i and Y = tensor Y_i with each factor dimension <= 3. We derive contraction inequalities, sum bounds, trace estimates for density operators, Lipschitz continuity (including singular limits), and limiting behavior for Cesaro means and infinite products. For density operators, we obtain an exact closed-form bijection between OLC and von Neumann
entropy for
qubits; prove this bijection does not exist for d >= 3; and establish upper/lower
entropy envelopes at fixed condition number, showing the admissible range [S_min(kappa), S_max(kappa)] satisfies ln 2 <= S_max(kappa) < ln 3 for every kappa > 1. The
qubit case recovers, as an operator lift, the classical Michelson-Jensen-Shannon equivalence of Bruni, Rossi, and Vitulano, while a counterexample shows this equivalence fails for d > 2 as a direct consequence of the non-bijectivity.
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Optics
Self-powered InAs nanowire detector arrays for extended-SWIR spectrometry at room temperature
Yang Yu, Wei Wen Wong, Zhe Li et al. (+16 more)
Spectral sensing in the extended shortwave infrared (e-SWIR) is important for molecular analysis, infrared imaging, and machine
vision, motivating the development of compact spectrometers for broader applications. However, conventional commercial off-the-shelf spectrometers in this wavelength region are expensive and bulky due to their reliance on external dispersive optics/filters and/or cryogenic accessories. Other emerging computational spectrometers are based on Si and InGaAs photodetectors that remain focused on the visible and near-infrared, with few detector platforms operating in the e-SWIR regime that simultaneously provide broadband sensitivity, low-noise room-temperature operation, and diverse spectral signatures for accurate identification and reconstruction. Here, we report a room-temperature e-SWIR computational spectrometer based on InAs/InP core-shell nanowire photodetector arrays with geometry-encoded spectral responses. The detectors exhibit self-powered broadband photoresponse across the 1–3 $\mu$m range, with responsivity up to 0.215 A W$^{-1}$, detectivity up to $1.6 \times 10^{9}$ cm Hz$^{1/2}$ W$^{-1}$, and microsecond response times. The excellent detector performance is leveraged to demonstrate filter-free spectral reconstruction using a compact multipixel photodetector array device. This enables high-accuracy molecular absorption spectrum reconstruction and hyperspectral imaging. Our results indicate that InAs nanowire arrays are a promising platform for compact computational spectrometry and imaging in the e-SWIR at room temperature.
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All authors Yang Yu, Wei Wen Wong, Zhe Li, Dawei Liu, Jinyuan Chen, Seyed Saleh Mousavi Khaleghi, Yue Bian, Kosala Dhanawansha, Li Li, Hongwei Liu, Xiaoxue Xu, Monica S. Allen, Jeffery W. Allen, Hark Hoe Tan, Chennupati Jagadish, Kenneth Crozier, Ziyuan Li, Chaohao Chen, Lan Fu
Optics · Cross-listed from physics.atm-clus
Core-Level Spectroscopy Decodes Bond-Alternation Dynamics of Cyclo[18]Carbon
Minrui Wei, Zeyu Liu, Sheng-Yu Wang et al. (+4 more)
The advent of X-ray free-electron
lasers and high-harmonic generation has made time-resolved X-ray spectroscopy a powerful tool for probing local atomic environments, yet whether localized core excitations can report on global collective distortions remains open. Cyclo[18]carbon (C$_{18}$), with its polyynic ground state (D$_\text{9h}$) and cumulenic transition state (D$_\text{18h}$), provides an ideal model to address this long-standing issue in bond-length alternation (BLA) dynamics. Mapping two-dimensional potential energy surfaces by first-principles simulations, we find that core ionization symmetrizes the ground-state double-well potential along the BLA coordinate. Our calculated X-ray spectra reveal remarkable sensitivity to bond-length variations: C1s ionization potentials vary by up to 2.4~eV across the BLA coordinate (1.1–1.4~Å), with a 0.9~eV variation for minima predicted by different functionals, while NEXAFS $\pi^*$ peaks shift by up to 4~eV across the same coordinate. These predicted signatures provide a quantitative spectroscopy–structure dictionary for decoding transient structures in future ultrafast X-ray experiments and monitoring bond-alternation dynamics in real time.
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All authors Minrui Wei, Zeyu Liu, Sheng-Yu Wang, Jun-Rong Zhang, Lu Zhang, Guoyan Ge, Weijie Hua
Optics
Pulse-by-pulse programmable synthesis of ultrafast optical waveforms
Shilong Liu, Gabriel Demontigny, Émile Dessureault et al. (+2 more)
Programmable control of individual pulses in a high-repetition-rate (typically MHz) ultrafast pulse train is a long-standing goal for optical arbitrary waveform synthesis. Here, we report a programmable pulse-by-pulse shaper that enables deterministic spectral-temporal control of ultrafast pulses at a repetition rate of $\sim$ 20~MHz. By synchronizing an FPGA-driven electro-optic modulation on the stretched waveform in a temporal 4$f$ shaping system, the regime writes pulse-index-dependent spectral phase profiles onto individual pulses. We demonstrate three levels of programmable ability: zero-order phase coding that maps pulse-by-pulse phase sequences into double-slit-like spectral-temporal interference; first-order phase programming that produces arbitrary temporal trajectories with deterministic delay; and fractional-order phase engineering that generates programmable temporal breathing. By launching the shaped pulse train into a nonlinear fiber stage, the programmed temporal breathing is converted into one spectral breathing. We further construct a phase-level-dependent regime map of nonlinear spectral breathing, revealing transitions from weak single-envelope breathing to multi-peak spectral splitting and strongly breathing merged-spectrum dynamics, in agreement with numerical simulations. This pulse-by-pulse spectral-temporal synthesis platform establishes pulse index as a programmable degree of freedom for ultrafast pulse shaping and provides a route toward real-time and pulse resolved optical arbitary waveform synthesis.
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All authors Shilong Liu, Gabriel Demontigny, Émile Dessureault, Stéphane Virally, Denis V. Seletskiy