ALT We investigate three-dimensional spatiotemporal optical vortex solitons (light bullets with a toroidal shape) carrying higher-order orbital angular momentum in Kerr media with anomalous group-velocity dispersion and a transversely localized Gaussian profile of the linear refractive index. Stationary vortex bullets with topological charges (winding numbers) 1≤ ℓ ≤ 4 are obtained as numerical solutions of the three-dimensional nonlinear Schrödinger equation, and their existence, structure and stability are systematically analyzed. In terms of atomic Bose-Einstein condensates, these solutions represent matter-wave solitons with embedded vorticity. We examine the dependence of the solution families on the propagation constant, the depth and width of the guiding profile, and ℓ. It is found that the increase of ℓ requires one to use a stronger or wider waveguiding potential to sustain localized states satisfying the Vakhitov-Kolokolov (VK) stability criterion. VK-complying and non-complying

ALT Tapered optical fibers offer tunable dispersion and a small mode area, yielding high nonlinearity, which makes them ideal for nonlinear and quantum optics. Because phase-matched four-wave mixing strongly depends on dispersion, the taper diameter becomes a key parameter. For sub-micrometer tapers, identifying the exact diameter is challenging. Here, we show that when seeding with a broad spectrum, stimulated four-wave mixing yields a comb-like spectrum that is directly linked to the overall taper profile opening possibility for non-destructive evaluation of sub-micron taper. Our model based on joint-spectral amplitude includes the phase accumulated over the fiber length.

ALT Thermal light exhibits intensity fluctuations or photon bunching that has been used as a source of entropy or temporally correlated light. However, its low spectral density limits its use in practical applications like LIDAR. One method of remedying this is optical amplification to boost its brightness. In this paper, we show that the normalized second order coherence function g⁽²⁾(τ) of a thermal light source is preserved after amplification. We then use amplified thermal light to demonstrate a LIDAR raster scan of a building at 1.3 km with a depth resolution of 2 cm.

ALT A new approach of silicon-lithium niobate (Si-LN) grating couplers (GCs) with a fully-etched structure is proposed. The coupling strength is engineered through subwavelength structures, allowing improved directionality. The adjoint-based inverse design method is simultaneously adopted to achieve efficient coupling between photonic circuits and fibers. Considering the birefringence of LN, the proposed Si-LN GCs are optimized and fabricated for TE mode along the crystallographic Z and Y directions. The experimentally measured coupling efficiencies are -3.3 dB and -3.9 dB along the crystallographic Z and Y directions, respectively. The measured 3-dB bandwidths are broader than 54 nm and the back reflections can be suppressed down to -15 dB over 50 nm for both directions. The proposed Si-LN GCs are realized by only single-step Si etching, offering a practical solution for fast device prototyping in Si-LN photonic integrated circuits.

ALT Tight-binding photonics bridges condensed-matter physics and optics, providing a powerful framework for engineering band structures and topological phases with light. For photons, however, the vacuum is gapless, so resonators in air carry radiative tails that produce spurious long-range couplings. Here we embed resonators in a photonic band-gap vacuum (BgV), a photonic crystal whose band gap plays for photons the role vacuum plays for bound electrons. The BgV localizes each resonance exponentially, so designed short-range couplings define the lattice Hamiltonian. We thereby experimentally realize a faithful Benalcazar-Bernevig-Hughes Hamiltonian in an all-dielectric photonic crystal, resolving corner resonances and their orbitals in microwave measurements. Unlike the vacuum surrounding electrons, the BgV is itself designable, controlling relative couplings and closed-loop interference through its band dispersion and Bloch modes. Full-wave calculations and extracted models show that uni

ALT A charge in uniform motion carries a bound field that does not radiate. Transition radiation releases part of it at a boundary in space. We propose and analyze the case of radiation emission due to a boundary in time: a relativistic electron bunch passes through an aperture in a semiconductor (silicon) wafer, and while its bound field occupies the wafer, a femtosecond laser switches the semiconductor into an electron-hole plasma. The field is a valid solution of the old medium and not of the new one, so it is handed to the plasma as an initial condition for radiation emission at the plasma frequency. Because in temporal transition radiation (t-TR) the wavevector is conserved, and the frequency is not, the emission can appear in a spectral band that the bunch's own field does not populate. Every electron contributes in phase to the initial condition at the switching moment, so the emitted energy scales as N². We derive the field energy conversion at the temporal boundary and the resulta

ALT The spatial distribution of energy in silicon thin films under femtosecond laser irradiation is demonstrated to be influenced by the interaction between carrier-induced refractive index modulation and self-induced Fabry-Pérot resonances. We resolve three characteristic excitation regions such as interface-localized, binodal and multi-nodal regimes considering the analysis of silicon-on-insulator (SOI) configurations across thicknesses of 100, 230, and 350 nm. We report a nonlinear hotspot migration effect where the transient reduction of the refractive index stretches the internal standing wave, translating intensity antinodes toward the film volume during the pulse. Numerical results demonstrate that at higher fluences, plasma-induced extinction suppresses internal reflections, triggering a transition from resonance-mediated absorption to plasma shielding. These findings establish a physical basis for depth-resolved modification in laser nanomanufacturing, providing a dual-capacity fo

ALT Detecting chirality is essential in chemistry and biomedicine. Circular dichroism identifies chiral molecules through their differential absorption of circularly polarized light. However, its sensitivity is limited by vanishing absorption at low concentrations. Fluorescence-based methods have already enabled other optical techniques to reach the single-molecule limit and could, in principle, also extend chiral detection to reach this sensitivity regime. They are marred, however, by the combination of weak fluorescence signals and low polarization contrast. To overcome these limitations, we leverage high-index dielectric nanophotonics to simultaneously enhance both fluorescence and polarization for chiral sensing. We propose a reciprocity-based analytical framework for a chiral dipolar emitter coupled to a nanoantenna and reveal the different contributions and trade-offs governing the enhancement of circularly polarized fluorescence. Guided by this insight, we tailor achiral dielectric

ALT Orbital angular momentum (OAM) represents a fundamental degree of freedom (DoF) for understanding novel phenomena in solids and synthetic lattices. However, the generation and control of OAM in lattice systems remain challenging. Here, we experimentally observe valley-controlled OAM states in inversion-symmetry-broken photonic honeycomb lattices consisting of s- and higher-orbital sublattices. These OAM states manifest as chiral vortex arrays in real space. By selectively exciting s-orbital modes carrying no initial OAM at either the K or K' valley, we observe higher-orbital OAM modes generated via inter-orbital coupling in neighboring sites. Specifically, s-p orbital coupling generates OAM states with topological charge l=+1 or l=-1, while s-d orbital coupling yields higher-charge OAM states with l=+2 or l=-2. The sign of the topological charge is determined by the valley DoF, enabling deterministic control of vortex chirality across the entire array. Our theory further reveals that a

ALT At a spatially uniform, in-plane-isotropic time boundary, the transverse displacement of a spatiotemporal optical vortex changes sign with its topological charge, despite a charge-independent conversion weight. Radial spectral filtering couples to the vortex phase while preserving identical converted spectral intensities for opposite charges. For a narrow scalar Gaussian spectrum, the displacement follows the logarithmic slope of the spectral weight and occurs with zero mean transverse momentum. In a finite pumped GaAs waveguide, unequal attenuation during extraction adds angular deflection. Independent Maxwell–Drude simulations test this extraction-induced response and give ±42 mrad before detector filtering. Calculated centroid traces at multiple planes separate propagation-induced drift from position offsets.

ALT Reconstructing a gradient-index (GRIN) medium consists of determining a spatial refractive index distribution that produces a prescribed ray trajectory, an inverse problem in geometrical optics. Previous approaches have used geometrical symmetries and conserved ray quantities to address this inverse problem. Extending reconstruction to freeform media requires approaches that do not rely on these symmetries. Here, we present a three-dimensional point-wise method for reconstructing freeform GRIN media through the inverse application of local refraction. The method does not require geometrical symmetry, paraxial approximations, or prior knowledge of the iso-indicial surfaces, and is straightforward to implement. Reconstruction using two interface geometries demonstrates that different refractive index distributions can be obtained from the same prescribed trajectory function. The choice of interfaces thus provides an additional degree of freedom for optical design, subject to local refrac

ALT Optical frequency combs have transformed molecular spectroscopy by enabling broadband, high-resolution analysis, yet they are conventionally used as light sources to interrogate external samples. Here, we introduce an integrated microcomb sensing architecture that unifies resonantly enhanced evanescent sensing with multiwavelength molecular fingerprinting in a single ultrahigh-quality-factor silica microresonator. Gaseous analytes interact directly with the evanescent field of light recirculating within the resonator, enhancing sensitivity while encoding analyte-induced perturbations across the microcomb's collective spectral response. Rather than relying on a single optical resonance, we exploit distributed responses across multiple comb lines to generate multidimensional molecular fingerprints. Adding more comb lines systematically improves analyte discrimination, showing that the microcomb provides sensing information beyond what individual spectral channels offer. Using methane as

ALT Engineering local optical chirality in planar photonic structures offers a route to selective and enhanced light-matter interactions with chiral media. Here, we introduce periodic dielectric waveguides that support chiral evanescent fields through the interaction of two nearly degenerate waveguide modes. We develop a perturbation theory for such a waveguide covered by a chiral layer, relating chirality-induced modal coupling and propagation-constant corrections to measurable intermodal power conversion and differential transmission. Whereas modal detuning confines the chiral response of a symmetric waveguide to a narrow spectral range, mode hybridization in an asymmetric waveguide creates individual eigenmodes that carry nonzero local chirality over a broad spectral range. We show that modal dichroism in realistic lossy waveguides can produce a significant background differential transmission signal. Such a background, however, can be suppressed by comparing transmission through two as

ALT Quantum frequency conversion (QFC) enables optical interfaces between dissimilar quantum systems, but suppressing noise while maintaining high conversion efficiency remains challenging. Here, we demonstrate that adapted poling in thin-film lithium niobate (TFLN) waveguides reduces the pump-power requirement while shifting the dominant noise mechanism and its power scaling. In 2-cm-long waveguides, adapted poling enables maximum conversion efficiency at an on-chip pump power of 19±0.8 mW, reducing the required pump power by 8 dB and the total conversion noise by 14 dB relative to conventional periodic poling at their respective maximum-conversion operating points. Controlled measurements with different pump conditions and device configurations reveal a transition from predominantly quadratic noise scaling in periodically poled devices to predominantly linear scaling in adapted-poling devices. This transition accompanies a shift from noise dominated by cascaded second-harmonic generation

ALT Single-shot coherent Rayleigh-Brillouin scattering (CRBS) requires dual colour, frequency, and pulse duration agile laser systems, currently available only in laboratory layouts. In this work, we present a compact, portable, and robust next generation laser system that meets all of these requirements. Key features include an integrated master-slave seed laser design for stable frequency chirping, fiber-coupled acousto-optic modulator (AOM) gated pulse shaping for long-term thermal stability, and customized amplification stages in a rugged, portable enclosure which simplifiy the alignment and maintenance process. The system in this implementation can deliver up to 450 mJ per arm, chirp rates up to ∼22 MHz/ns, and arbitrary temporal profiles within ∼25 ns to ∼1 μs. This laser system is validated by measuring the neutral number density of an atmospheric plasma jet, and a two-dimensional temperature map is constructed, demonstrating lab-grade diagnostics for field deployment.

ALT Universal function approximation underpins neural networks' capacity to represent nonlinear relationships, but realizing this capability in optical hardware requires engineering the computational features encoded in light. Here, we show that wavelength diversity enhances optical function-approximation expressivity through wavelength-scaled Fourier features generated by a shared phase encoder, without increasing the number of input-encoded harmonics. Multiple wavelengths contribute to the representation of each output function rather than merely serving as independent computational channels. We establish theoretical scaling laws and approximation-error bounds, revealing that, for nondispersive encoders, the spectral endpoints determine the accessible computational bandwidth, while intermediate illumination wavelengths enrich the available harmonics within that bandwidth. Numerical studies demonstrate improved approximation of real- and complex-valued nonlinear functions, with a represen

ALT Conservative nonlinear waves generally undergo an irreversible process of thermalization toward the Rayleigh–Jeans (RJ) equilibrium state. Light thermalization has recently been experimentally investigated in the two-dimensional transverse spatial dynamics of multimode waveguides. Here, we consider the one-dimensional temporal dynamics of incoherent light propagating in a weakly birefringent single-mode fiber. We show that light thermalization is responsible for a self-polarization of the incoherent wave during its propagation. Within the framework of wave turbulence theory, we show that this phenomenon originates from a nonequilibrium process of adiabatic cooling: polarization fluctuations are continuously transferred toward the high-frequency tails of a local RJ equilibrium state, whose effective temperature decreases during propagation, thereby increasing the degree of light polarization. Moreover, in the absence of a high-frequency cut-off that would regularize the ultraviolet cata

ALT A membrane traversed by a dense array of nanochannels acts as a photonic metamaterial: with channels far smaller than the wavelength of light, the optical response is set by the architecture rather than by the constituent materials. Here each nanochannel is turned into a nonlinear optical meta-atom by filling anodic aluminum oxide (AAO) with benzil (BZL), a noncentrosymmetric molecular crystal, and the crystallization pathway programs their orientation. In free-standing membranes every channel solidifies independently, the orientations remain uncorrelated, and the effective second-harmonic generation (SHG) response is nearly polarization isotropic; its magnitude follows a core - shell model in which an optically inactive interfacial layer of 2.6 nm reduces the active volume of each meta-atom, reproducing on bare alumina the value previously found on alkyl-grafted silica and indicating a host-insensitive limit. Seeding crystallization from a bulk benzil layer instead aligns the meta-ato

ALT Silicon nitride has emerged as a key material for the advancement of future quantum communication and computational devices. However, challenges persist in establishing a comprehensive development process, spanning from fabrication to optical characterization, essential for advancing these devices to their next stage of potential. Maintaining control over the entire process, from start to finish, alongside device modeling, enables more efficient and timely iteration and optimization. Here we introduce a fabrication-to-benchtop process. We employ an in-house stoichiometric recipe for device fabrication and conduct comprehensive characterization of optical losses and material properties. Understanding and controlling the refractive index of the device are vital for predicting device geometries and group indices. Implementing the refractive indices of our fabricated devices, we simulate microring resonators and demonstrate their application in generating optical solitons.

ALT We describe the nanofabrication and loading of lithographically patterned, high aspect ratio 10 μm diameter silicon dioxide discs with thickness of 400 nm into an optical standing wave trap in vacuum. We obtain motional spectra of the center of mass motion of the discs using a combination of interferometric and imaging methods. The method is capable of high-efficiency loading and optical trapping using small numbers of objects, of the order of a few particles, with customized geometries and sizes compatible with wafer scale nanofabrication methods. Disc-like particles in optical traps have been identified as promising candidates for detectors of high frequency gravitational waves or as sensitive accelerometers.