ALT A small change in parameters leads to a small change in the outcomes, in most cases. For instance, an optical vortex ring, created in the superposition of two laser beams, can slightly shrink if the phase changes minutely. However, dynamical systems can also experience significant changes due to small perturbations in parameters; the vortex rings can reconnect, nucleate or collapse into a point. Parameters that cause such striking outcomes are at the focal point of catastrophe theory - a branch of bifurcation theory that studies degenerate critical points of a potential function. We present theoretical study of topological configurations of optical vortex rings in elliptic Gaussian beams, which change dramatically at specific beam parameters. We identify two types of catastrophes, cusp and butterfly, near which very small changes of elliptic deformations lead to complex topological transformations of vortex rings.

ALT This work presents a surface-illuminated lateral Ge-on-Si interdigitated separate-absorption-charge-multiplication (SACM) avalanche photodiode for 1550-nm detection. The intrinsic-region spacing, P⁻ charge-control width, and finger geometry are engineered to suppress high-field penetration toward the Ge/Si heterointerface and localize avalanche multiplication in Si. Simulations show that wider charge-control or intrinsic regions reduce fixed-bias dark current and shift avalanche onset to higher reverse bias. Among the tested structures, the intrinsic-region spacing/P⁻ charge-control width of 0.5/0.15 μm achieved a peak responsivity of 11.81 A/W at 1550 nm. At a -20 V applied voltage, it exhibited a multiplication gain of 3.796, a 3-dB bandwidth of 7.13 GHz, and a matched-bias gain-bandwidth product of 27.07 GHz. Optical-power-dependent measurements also show avalanche-gain compression consistent with space-charge screening. These results demonstrate effective lateral-field engineering

ALT Metamaterials, which store, guide and emit waves through their eigenmodes, have enabled the development of devices with unprecedented functionalities. Yet the spatial profiles of conventional metamaterials' eigenmodes are typically determined by their pre-determined structures (Hamiltonians). In this work, we introduce `wavefunction-templated metamaterials', a class of physically realizable metamaterials hosting diverse prescribed, spectrally isolated eigenstates. The resulting Hamiltonian geometries obey a boundary law, with the required nonlocality determined solely by single-contact boundary sites, independent of the state interior or lattice size. The sparse Hamiltonians are then Hermitianized, followed by spectral reshaping to open a protective gap around the target eigenstate. We validate our approach in discrete lattices and acoustic metamaterials. Although demonstrated in acoustics, the principle can be applied to thermal, electrical-circuit and photonic metamaterials.

ALT The topological charge of a bound state in the continuum (BIC) can flip when the BIC merges with other polarization singularities or, as recently shown, at band flips. Here, using a coupled-mode analysis, we derive an analytical expression for the topological charge of symmetry-protected BICs in one-dimensional single-layer photonic lattices. The expression captures both merging-induced and band-flip-induced charge flips. We find that, during a band flip, the topological charge of the BIC reverses with the formation of lines of circular polarization that cross at the Γ point. In vertically symmetric lattices, each charge flip occurs simultaneously in the upward and downward radiation channels. Breaking vertical symmetry makes both kinds of charge flips channel-differentiated, creating a parameter interval in which the BIC carries opposite topological charges in the two channels and forms a Janus BIC. We show that Janus BICs also emerge in experimentally accessible one- and two-dimensio

ALT A technology for the in situ formation of a three-layer TiNₓ/Ti/TiNₓ functional material within a single vacuum cycle is presented, together with the results of investigations of its structural and electrophysical properties. The maximum critical power density reached approximately 140 MW/cm². Under continuous operation at 90% of the critical power, the structures remained operational for 24 h. The characteristics of microbridges without and with a protective SiOₓ layer were compared. The presence of the coating modifies the electrothermal operating regime of the structures and enables estimated temperatures of approximately 500-700 degrees Celsius to be reached.

ALT Silicon is the dominant platform for integrated photonics, yet its wide electronic bandgap of 1.1 eV fundamentally prevents efficient detection of mid-infrared (MIR) photons through direct valence band to conduction band excitation. Existing approaches therefore seek to enhance sub-bandgap absorption or introduce external infrared absorbers. Here we demonstrate a profoundly different detection strategy based on optically gated transduction, in which MIR photons modulate a pre-established excitation state rather than directly generating photocarriers. Our device integrates Nd3+-doped lanthanide nanoparticles with an inverse-designed Al/p-Si metasurface supporting dual resonances that simultaneously enhances optical gating in the near infrared and resonantly couples incident MIR radiation. The MIR illumination redistributes the Nd3+ emission pathways, producing an optical-state change that is converted into an electrical signal through a silicon Schottky junction. The device achieves roo

ALT Compact optical systems with continuously tunable focal lengths are highly desirable for machine vision, biomedical imaging, and miniaturized cameras. Rotational Moiré lenses offer a planar approach to focal-length tuning, but metasurface-based implementations typically require complex nanofabrication processes that complicate large-area production. Here, we present a cyclic, mask-free fabrication strategy that combines layer-by-layer self-assembly of two-dimensional graphene oxide (GO) and poly(diallyldimethylammonium chloride) (PDDA) with femtosecond laser nanoprinting. Repeated GO-PDDA assembly and spatially selective ablation enable atomic-scale thickness control and the construction of precise multilevel phase profiles, reducing phase-quantization errors and improving focusing efficiency. The measured focusing efficiencies of individual GO lenses increase from 22.4% for two phase levels to 54.8% for six levels. Using this six-level modulation strategy, the fabricated GO Moiré lens

ALT Live-cell imaging of cellular and tissue samples relies predominantly on optical modalities, such as fluorescence, confocal, and multiphoton microscopy, in which cellular information is encoded in emitted photons. Photons scatter and attenuate in biological samples, restricting depth resolution, while the excitation light required to produce them induces photodamage that perturbs the very biology under observation. Magnetic fields, by contrast, traverse biological samples without attenuation at cellular length scales, but the imaging modality that extracts the encoded information, magnetic resonance imaging, cannot resolve individual cells. Here we present Quantum Cell Monitoring (QCM), a widefield nitrogen-vacancy magnetometry platform that encodes single-cell information in stray magnetic fields rather than emitted photons and reads it out at subcellular resolution. Integrated with a specialized live-cell incubator, QCM tracks magnetically labeled living cancer for up to 72 h through

ALT Coherent optical modulation of free-electron wavepackets offers a route to ultrafast beam steering, energy exchange, temporal compression, and quantum-state shaping. Recent advances in photon-induced near-field electron microscopy (PINEM), ultrafast Kapitza-Dirac effect (KDE) and dielectric laser acceleration (DLA) have demonstrated strong light-electron coupling, but longitudinal energy modulation, transverse momentum transfer, and wavepacket-dependent diffraction are still commonly described with separate models. Here, we develop a unified Light-Electron Modulation (LEM) framework that treats optical near fields as programmable phase modulators for free-electron wavepackets. Within this framework, we identify longitudinal and transverse modulation channels, analogous to electro-optic phase modulation and acousto-optic diffraction of light, respectively, and show how their operation depends on wavepacket extent, recoil, phase matching, and optical-field geometry. This formulation orga

ALT Estimating the separation of two unresolved or nearly unresolved sources from recorded intensity images is difficult when source brightness, mutual coherence, and phase are unknown and the point-spread function (PSF) departs from a Gaussian. We formulate Hermite–Gaussian (HG) projections of one- and two-dimensional Airy amplitudes and prove that ratios of mode probabilities with equal longitudinal parity exactly cancel the brightness, coherence, and phase nuisance parameters under a symmetric two-source model. For a one-dimensional Airy slice we achieve an explicit multi-ratio separation inversion. For the physical two-dimensional circular-pupil PSF we obtain exact finite-pupil overlap integrals and locally invertible separation responses. Motivated by these analytical invariants, we examine Airy-informed convolutional neural networks (CNNs) on synthetic Airy images with known separations. At 150,000 training images, the approximate mean absolute errors are 0.018 in plotted separation

ALT High-order harmonic generation (HHG) in solids provides a compact and coherent EUV radiation, which has attracted considerable attention. Many theoretical methods for laser-crystal interactions are developed. However, an approach to treat large-scale amorphous systems with ab-initio accuracy is still lacking because of the enormous computational cost. Here, we incorporate molecular dynamics and tight-binding electron Hamiltonians based on deep-learning methods to solve the problem efficiently. Its accuracy is validated by comparing the HHG spectra of monolayer hexagonal boron nitride (h-BN) with those obtained using existing methods. Then we use it to study the temperature-dependent HHG in bulk Si. We uncover a distinct harmonic-order-dependent thermal response: low-order harmonics are enhanced with increasing temperature, whereas high-order harmonics are suppressed. The former is caused by the modification of the inter-site hopping in the system, while the latter is mainly influenced

ALT High-refractive-index nanowires are of interest for signal enhancement in fluorescence-based biosensing. Here, through electromagnetic modelling, we demonstrate substantial fluorescence signal enhancement by incorporating a tapered section into a cylindrical nanowire and investigate two complementary tapering configurations to address practical implementation challenges. Under near-normal excitation, the excitation enhancement increases approximately linearly with taper length, reaching more than three times that of the corresponding non-tapered nanowire at a taper length of 8000 nm. In a non-imaging signal detection scheme using a low numerical aperture (NA), the proposed tapered nanowire achieves more than three orders of magnitude enhancement in fluorescence signal compared with a planar biosensor. Thus, the tapered nanowire should enable efficient fluorescence detection using compact, low-NA optical configuration. In imaging mode, similarly as for non-tapered nanowires, imaging sha

ALT Photopic luminous efficacy (lm/W) weights optical power strictly against human eye sensitivity V (lambda), creating a systemic metrological penalty for electric light sources engineered with broad spectral output in the ultraviolet (280-380 nm) or infrared (780-4000 nm) bands. Similarly, metrics evaluating chromaticity, color quality, or melanopic pathways assess photoreceptor responses strictly within the visual band, offering no measure of broad-spectrum physical radiant power conversion. To resolve this limitation, we introduce Daylight-Referenced Efficiency (eta_DRE), a radiometric framework that evaluates how efficiently an electric light source converts electrical power into an optical spectrum matching natural terrestrial daylight across domain Omega = [280 nm, 4000 nm]. The framework factorizes performance into primary physical quantities: domain-restricted Wall-Plug Efficiency (etawall [Wₒptical/Wₑlec]), measuring unweighted electrical-to-optical conversion, and Daylight Spect

ALT Enabled by their controllable optical anisotropy, liquid crystals form a cornerstone of linear optical and display technologies. Bringing the versatile platform into the nonlinear regime, we explore its nonlinear optical anisotropy by high-order harmonic generation spectroscopy. Through a comprehensive study targeting gas, liquid, nematic, and crystalline phases, we present a semi-empirical tight-binding approach that provides insight into the intermolecular character of ultrafast light-driven electron dynamics across soft-matter mesophases. We demonstrate how intermolecular electron hybridization enables spectroscopic access to structural properties, such as the nematic director and order parameter. Outlining such foundational mechanisms opens avenues towards nonlinear liquid crystal devices and ultrafast soft-matter spectroscopies.

ALT High harmonic generation in solids is typically described under the assumption of a stationary medium. This assumption is rarely questioned because the electronic properties of most media evolve on timescales much slower than the harmonic emission process itself. However, in strongly driven time-varying transparent conductive oxides the plasma frequency, carrier density, and effective mass can evolve on the same femtosecond timescale as harmonic generation. Under these conditions, harmonic generation and material evolution are no longer independent processes. Within this context, we consider a two-field pumping scheme in which a strong field generates a comb of high-order harmonics across a broad spectral window, while a weaker field simultaneously reshapes its own individual spectral lines. Distinct from geometry-dependent wave-mixing processes, the evolving electron plasma reshapes multiple collinear harmonic channels simultaneously. A fully self-consistent hydrodynamic-Maxwell frame

ALT For a complex wave, the local phase variation provides the instantaneous frequency in time, the local wavenumber in space, and the local momentum in quantum mechanics. Here we study this quantity from the complex-zero structure of the analytic continuation of the wave. A single nonreal zero produces a localized Lorentzian phase variation on the real axis, whose position, width, sign, amplitude, and integrated phase are fixed by the zero itself. We call this elementary zero-associated oscillation a chirpon. The representation is exact for finite products and finite Fourier sums, and extends to entire and band-limited functions through canonical factorization. We illustrate the construction with superoscillatory sequences and discrete Fourier sums, showing how local anomalous oscillations can be reconstructed from periodic families of complex zeros. We further show how linear systems transform chirpons through the displacement of their associated complex zeros, and illustrate this dynami

ALT Directly modulated vertical-cavity surface-emitting lasers (VCSELs) are central to short-reach optical interconnects, where modulation bandwidth and power efficiency are critical factors for increasing data transfer capacity. Conventional oxide VCSELs still require power-hungry signal processing to achieve high-speed data transmission above 100 Gb/s. Here we report an experimental implementation of detuned loading in a VCSEL to enhance the modulation bandwidth. The detuned loading is achieved by carrier-induced index variations that reshape an engineered transverse mode so its overlap with spatially selective optical losses decreases with increased carrier density. This produces a negative differential loss reminiscent of that in detuned-loaded DBR lasers lasing on the long-wavelength reflectivity flank. The resulting 850 nm single-mode VCSEL exhibits an enhanced carrier-photon relaxation frequency of 44 GHz, yielding a 3dB electrical modulation bandwidth exceeding 50 GHz. The enhancem

ALT The rapid growth of artificial intelligence (AI) has increased the demand for energy-efficient hardware, and optical computing has emerged as a promising alternative to conventional electronic processors owing to its high parallelism and potentially lower power consumption. In this work, we investigate an optical computing architecture based on an integrated photonic circular multipass cell, focusing on its suitability for machine learning and pattern recognition tasks. The properties of the system are evaluated through measures of nonlinearity and cosine similarity, which characterize the system's information-processing capacity and the dimensionality of the generated feature representations. Numerical results demonstrate that the reservoir mirror reflectance, the size of the encoded figure, and the refractive-index contrast between the reservoir and the encoded figure modify the nonlinearity of the system, as verified via pairwise similarity estimates. These results indicate that the

ALT We present a parameter-decoupling-informed learning model for estimating subwavelength separations of point sources, without requiring prior knowledge of source properties, control over the sources, or continued access to their light signals. The method builds on our parameter-decoupled quantum superresolution estimation theory, which circumvents the need to estimate nuisance parameters such as partial coherence, brightness imbalance, and relative phase. Our convolutional neural network further accommodates practical imperfections, including background noise, photon loss, and centroid and orientation misalignment. We validate the method using synthetic and experimentally generated images, achieving separation-estimation fidelity above 82% for separations as small as approximately 0.075σ, where σ is the Gaussian intensity-PSF standard deviation. This corresponds to an illustrative separation of ∼13.5 nm when σ=180 nm, suggesting potential relevance to length scales addressed by advanced

ALT Accurately simulating high-order harmonic generation (HHG) for attosecond science requires connecting the microscopic single-atom quantum dynamics and the macroscopic propagation of intense driving laser fields. HarP is an open-source Python code designed to address this multiscale problem. It solves the wave equations for both the driving laser field and the generated harmonics, using precomputed dipole tables for the nonlinear polarization density. This tabulation enables the direct integration of accurate microscopic models while avoiding costly calculations during the propagation. The methodology builds upon the approach of [L'Huillier et al. (1992) PRA 46, 2778] and has already facilitated multiple studies on phase matching, propagation effects and HHG optimization. This paper presents the underlying physical model, its numerical implementation, and comparison against alternative simulation frameworks.