Optics Papers

ALT Fiber-optic parametric amplifiers in a phase-sensitive amplifier (PSA) configuration are well known for their low noise properties. Quantum mechanics dictates that these amplifiers can have a 0 dB noise figure (NF) (ratio of signal-to-noise ratio at the input and output of the amplifier) under certain conditions. However, for a dual-pump configuration, when the system is highly nonlinear, fully quantum calculations of NF become non-trivial. In such cases, semi-quantum models of NF evaluation exists, however, they are often complicated and resource intensive. To simplify that, in this work, first we use a semi-quantum NF calculation framework for the generation of numerically simulated input-output dataset of NF over a large parameter spaces. Then we use the data to train an optimized deep neural network (DNN) for rapid NF prediction. Utilizing the DNN, we demonstrate about 400 times reduction in the computation time compared to the standard semi-quantum NF evaluation approach with a me

ALT Optical topological quasiparticles such as skyrmions and merons consist of engineered electromagnetic fields which can be realized via the controlled interference of polaritons. The resulting polaritonic topological lattices offer a promising platform for on-chip information encoding and nanoscale light-matter interaction. However, realizing these functionalities requires active tailoring of the polaritonic topological lattice. Although previous works have achieved tuning of the size of the polaritonic lattice sites, these methods relied on cumbersome and time-consuming fabrication processes and do not allow reconfiguration of the topological invariant. Here, we demonstrate fast optical prototyping of reconfigurable hexagonal and square coupling structures for the generation of polaritonic topological lattices with hyperbolic phonon polaritons in hBN using the phase-change material In₃SbTe₂. As In₃SbTe₂ can be switched reversibly between its dielectric (ε>0) amorphous and metallic (ε<0

ALT Driven nonlinear photonic lattices can settle into steady, symmetry-broken, periodic, or chaotic states, and mapping where each occurs in parameter space is key to device design. Brute-force mapping is slow and relies on hand-built criteria, while machine-learning classifiers are usually tested on different systems, so it is unclear which suits a new lattice. We therefore apply four classifiers to the same coherently driven Su-Schrieffer-Heeger (SSH) chain of Kerr resonators: a hand-built heuristic classifier based on Lyapunov exponents and spectral diagnostics, a supervised convolutional neural network (CNN) trained on the heuristic labels, an unsupervised library-building scheme based on augmented dynamic mode decomposition (aDMD), and an unsupervised Gaussian mixture model (GMM) on four dynamical invariants that include an aDMD reconstruction error. Using a converged heuristic diagram as the reference, the CNN reaches 98.0% held-out accuracy, while the two label-free methods reach a

ALT A metasurface is an electrically thin interface that controls the phase, amplitude and polarization of a wave, upon reflection or transmission. Printed on a grounded dielectric substrate and spatially modulated across the aperture, it converts a guided surface wave into a radiated leaky wave, a mechanism used in holographic metasurface antennas. Controlling this conversion requires synthesizing a prescribed distribution of admittance tensors, each derived from the homogenization of a subwavelength unit cell. Many numerical and semi-analytical methods have been proposed to relate the geometry of a meta-atom to the tensor it produces. This paper presents, to the author's knowledge, the first analytical model, restricted to elliptical meta-atoms on a uniform lattice. The Galerkin method is applied directly to the geometry of the patches, without spatial meshing. An affine transformation maps any rotated ellipse onto the unit disk, so that a single formulation covers every configuration. A

ALT Inverse design of dielectric metasurfaces is powerful but labour-intensive: each new target requires choosing a parameterization and a figure of merit, managing compute resources, and critically assessing results that may be numerically unconverged, sensitive to fabrication errors or trapped in local optima. Here we present an open-source pipeline in which an artificial intelligence (AI) coding agent turns a plain-language specification into metasurface optimization runs, executes them, analyses every run with a fixed checklist and proposes the next iteration. Designs are optimized with differentiable three-dimensional rigorous coupled-wave analysis (RCWA), including robustness to fabrication tolerances, and every reported design is independently verified with finite-difference time-domain (FDTD) simulations. We demonstrate the workflow at 1550 nm on a freeform silicon metagrating, on a polarization-independent meta-atom library assembled into beam-deflecting supercells, and on metalen

ALT We report polarization- and angle-dependent lateral beam shifts observed at 458 nm upon reflection from a deep-ultraviolet (DUV) dichroic multilayer mirror. These Goos–Hänchen (GH) shifts originate from the phase of the complex Fresnel reflection coefficient and are quantitatively reproduced using a transfer-matrix model. Simultaneous reflectance (R), transmittance (T), and GH shift measurements provide complementary constraints on the coating's amplitude and phase response. The analysis is extended to transmission, predicting analogous phase-induced lateral shifts. In frequency-doubling cavities using dichroic mirrors, these phase effects can accumulate over multiple reflections, leading to deviations from ray-optics predictions that may affect cavity mode structure and resonance conditions. Our results show a GH shift of as much as 2 textmu m (≈ 4.4λ), which, combined with RT data, enables improved characterization of the phase response of the multilayer coating. The p-polarized refl

ALT Transponder-type heterodyne interferometry is a versatile metrological technique for high-precision measurements, with applications in Earth's gravity-field recovery, space-based gravitational-wave detection, deep-space ranging, and Doppler tracking. However, parasitic back-reflections can contaminate phase readout and degrade measurement sensitivity. To characterize and suppress this noise, we constructed a transponder-type interferometer with coaxially aligned counter-propagating beams, achieving stable operation at a received optical power of 720 pW. An adjustable reflecting system was introduced into the master-side transmit path to simulate back-reflection under realistic conditions. Optical path scans and model fitting showed that phase errors vary periodically with the relative phase between the main and parasitic interference signals, which defines the working point. Assisted by π measurement, adjustment to low-sensitivity working points was combined with balanced detection to

ALT Exceptional bound states in the continuum (EBICs) arise when bound states in the continuum (BICs) with distinct intrinsic losses coalesce at exceptional points (EPs), combining continuum-embedded wave confinement with a non-analytic spectral response. However, conventional EBICs rely on precisely controlled modal coupling and intrinsic loss, making them fragile and difficult to realize experimentally. Here, we introduce bulk-band topology to mitigate this fragility and experimentally realize a photonic exceptional topological BIC (ETBIC) in spoof surface plasmon polariton waveguides by merging two symmetry-protected topological BICs (TBICs) to coalesce at an EP, with the topological design supporting robust localization under symmetry-preserving perturbations. By engineering an intrinsic loss contrast and tuning the intermodal coupling, we directly resolve the coalescence of the complex eigenfrequencies, accompanied by measured near-field distributions consistent with the exceptional e

ALT Microheaters underpin a broad range of applications that require localized and dynamic thermal control. Engineering their spatial and temporal temperature distributions is therefore essential, yet conventional heater design relies largely on iterative trial and error involving numerous full-scale thermal simulations. Here, we introduce an inverse design algorithm for pulsed heating, a common operating modality in thermal processing, sensing, switching, and material characterization. The approach uses a single lithographic step to pattern the doped regions of a silicon microheater and, in principle, enables on-demand peak temperature distributions under transient voltage excitation within one closed design loop. The algorithm also incorporates practical fabrication constraints, including finite lithographic resolution. We demonstrate its versatility through three representative designs. First, an optimized heater achieves more than a 20-fold reduction in temperature nonuniformity compar

ALT The realization of high-performance femtosecond lasers on photonic integrated circuits (PICs) requires robust, low-loss coupling between a saturable absorber and a photonic waveguide. In this work, we demonstrate the hybrid integration of a semiconductor saturable absorber mirror (SESAM) with a silicon nitride (SiN) PIC by micro-assembly. This micro-assembly strategy transfers the non-linear functionality of the absorber onto the PIC. We characterize the linear and non-linear performance of an unbonded SESAM and of a SESAM bonded to inverse-tapered SiN waveguides. At 1560 nm, the bonded device shows a waveguide-coupled modulation depth of 5.2%, a maximum reflectivity of 37.2%, and a saturation fluence of 47 textmu J/cm². This work demonstrates that SESAMs can be integrated directly onto silicon nitride-based PIC platforms and provides a pathway towards fully integrated, self-starting, chip-scale ultrafast lasers.

ALT Intelligent metasurfaces enable advanced wave manipulation, including negative refraction, focusing, beam splitting and beam steering, with significant potential for practical applications. However, conventional approaches often rely on active metamaterials with gain, or demand computationally intensive solutions of inverse problems to find the optimal configuration. In this work, we use the scattering framework of quantum graph theory to derive an exact, analytic expression for configuration of a passive metasurface that produces a prescribed reflected wave field. The metasurface terminates a periodic lattice of waveguides and consists of an array of channels, each a tube of length ℓₘ ending in a vertex whose scattering parameter λₘ sets how much of the wave is lost to the wall. For any prescribed incident and reflected field, the exact lengths and scattering parameters follow channel by channel, in closed form, from the ratio of the wave amplitudes returning to and leaving the lattic

ALT Here, I study the conditions for realizing an axion topology in a homogeneous inversion-symmetric electromagnetic continuum, in the absence of a crystalline lattice. I introduce a continuum inversion invariant expressed solely in terms of the spectral properties of the material response in the zero- and infinite-wave-vector limits. Surprisingly, it is found that standard gyrotropic-type material responses are strongly constrained and, under fairly general conditions, cannot open an axion gap within first-order perturbation theory. Based on an analogy between the effective response of crystalline photonic axion insulators and the optical response of centrosymmetric altermagnets, a class of spatially dispersive odd magnetoelectric couplings that can open an axion gap is identified. These findings suggest an interesting hierarchy of nonreciprocal mechanisms in electromagnetic continua: while uniform gyrotropy relates to Chern phases, odd magnetoelectric coupling relates to axion phases.

ALT Short mode-evolution couplers have been designed with several seemingly different approaches, including fast quasi-adiabatic dynamics (FAQUAD), counter-diabatic (CD) driving realized by tailoring waveguide widths and spacing, CD driving realized by axis bending, and numerical optimization of the coupler geometry. Using exact two-mode coupled-mode theory in the Kramers–Henneberger frame of the bent coupler, we show that these approaches belong to the same design space. The three geometric parameters, width difference, spacing, and axis tilt, act on the light through two functions only: the coupling strength, set by the spacing, and an effective detuning, set by the width difference and the axis curvature. The gauge, bent, and mixed realizations of a CD coupler are therefore the same device and have the same bandwidth. The bandwidth is set by the angle χ between the light and the field that steers it on the Bloch sphere, integrated along the device as intsin²χ dz, and for a CD coupler th

ALT Ray tracing in X-ray science has typically been limited to descriptions where refraction occurs only at interfaces, ignoring the refraction occurring due to the continuous variations in index of refraction in the bulk of a material, as are common in biological samples like bone. We propose a method to simulate X-ray images directly on voxel grids using curved rays. We first validate this method compared to a model with an analytical solution, and then investigate the effects of voxel size, interpolation choice, and illumination to grid alignment on a few simulated test objects. From these investigations, we make several recommendations to guide simulations using these techniques.

ALT Conventional thermal emitters obey Kirchhoff's law of thermal radiation, which requires emissivity and absorptivity to be equal at each wavelength, angle, and polarization. This in turn places a fundamental limit on a range of radiative energy technologies as well as heat transfer. This constraint can however be overcome using magneto-optic semiconductors, which break Lorentz reciprocity under an applied magnetic field. However, in most prior experimental demonstrations, nonreciprocity has been restricted to TM polarization, since the electric field of TE-polarized light is parallel to the applied magnetic field. Here, we experimentally demonstrate nonreciprocal absorption in both polarizations at the same wavelengths and angles from a single structure, wherein a germanium Mie-resonant metasurface on a doped InAs layer scatters TE-polarized light into near fields with components perpendicular to the magnetic field, allowing the magneto-optic response of the InAs to act on them. Under a

ALT The formation and dynamics of dissipative solitons are governed by the interplay of dispersion and nonlinearity, alongside the gain-loss balance. While it is known that dispersion orders beyond the conventional second order support stable solitons, the possibility of the creation of dissipative topological solitons in this setting was not explored. Here, we reveal a class of stable dissipative solitons enabled by the pure-high-even-order dispersion (PHEOD), with dispersion orders m=4, 6, 8, and 10. The resulting dissipative topological solitons (DTSs) and moving topological solitons (MTSs) are dark-type structures featuring a zero-amplitude point that separates two CW backgrounds with opposite signs. In particular, the PHEOD solitons feature oscillatory tails, which are not present in the conventional dark states. The linear-stability analysis confirms full robustness of the PHEOD-supported DTSs and MTSs. We also explore collision dynamics of MTSs, whose repulsive interactions are inel

ALT Broadband nonlinear frequency conversion mixes multiple input frequencies, complicating the transfer of programmed spectral phase between widely separated spectral bands. Here we identify and experimentally realize a quasi-linear phase-transduction regime enabled by broad phase-matching acceptance and effective localization of the complex frequency-mixing response. This selectivity can arise from coherent interference without narrowing the pump spectrum. We implement this regime through dispersive four-wave mixing in an argon-filled hollow-capillary fiber, transferring spectral phase from 1032-nm near-infrared signals to 344-nm ultraviolet idlers. Transient-grating frequency-resolved optical gating reveals frequency-inverted, phase-conjugating transfer of quadratic dispersion, localized phase steps, and low-frequency sinusoidal modulation. After correction for the modeled pump-induced phase background, the quadratic and step responses exhibit approximately linear point-by-point correla

ALT In a spatially dispersive medium the electromagnetic energy and flux are given by the frequency and wave-vector derivatives of the constitutive parameters, a result known as the Agranovich–Ginzburg (AG) formulas. Here, we clarify the physical meaning of the derivative terms in these relations and show that they measure the energy and flux carried by the degrees of freedom of the internal field-matter dynamics that the Maxwellian constitutive description hides. We construct an extended state-space model of such dynamics for a wide class of temporally and spatially dispersive media, from which the Maxwellian constitutive relations follow upon elimination of the internal variables, the effective material operator resulting from the Schur complement of the eliminated internal block. A congruence identity relates this complement to the extended state-space description, which allows us to extend the AG formulas to general bianisotropic media and to establish the conditions of their validity

ALT We assess the reliability of localization precision predicted for a 1716-nanopillar dielectric metalens using a site-resolved complex RCWA library and a vectorial Poisson Fisher model. An independent calculation reproduces the archived local axial Cramer-Rao bound of 20.7738 nm to within 0.0044 nm, yielding 20.7695 nm under the same ideal detector and 3000 detected signal photons. High-order periodic-cell calculations reveal a 0.1335 rad phase difference at a selected diameter; different substrate-index assumptions prevent attributing this difference solely to modal truncation. Replacing the recalculated coefficients at 39 actual sites changes the bound to 20.7522 nm. Restricted phase-mask benchmarks and pixel-integration checks further distinguish a stable statistical prediction from electromagnetic convergence. We provide a reproducible, model-conditional benchmark, not a physical-device performance claim.

ALT Additive manufacturing is increasingly being explored as an approach for producing complex structures for optical hardware. In this work, we present a fully monolithic optomechanical chassis fabricated using laser powder bed fusion additive manufacturing. The structure was fabricated from thermally stable Invar36, a low-thermal-expansion alloy that enables high dimensional stability under varying environmental conditions. Our monolithic design incorporates embedded optical mounts, flexures, and alignment features directly into the chassis geometry that exceed the practical limits of conventional subtractive manufacturing. By integrating the optomechanical support structure into a single compact unit, the system achieves a reduced footprint compared to traditional optomechanical assemblies. The results demonstrate the potential of additive manufacturing to produce lightweight, and highly customized optical systems, opening the possibility of new pathways for next-generation quantum sens