Semiconductor lasers confront a fundamental power-beam-quality trade-off, as larger apertures excite higher-order modes. We present the gain and index tailored (GIT) cylindrical ring laser (CRL), which decouples power scaling from modal degradation via a ring resonator supporting radial multimode emission around its full 360 degrees circumference while maintaining a single epitaxial axial mode. This ensures a diffraction-limited vertical Gaussian profile regardless of aperture size, circumventing traditional limitations and elevating the catastrophic optical damage threshold. Validated by custom modeling, prototypes (3-5 mm diameter) achieved 10-14 W pulsed power. Scalable via lateral expansion or stacking, the architecture enables high-brightness emission for industrial and directed-energy applications. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
We investigate the influence of transverse-electric-transverse-magnetic (TE-TM) splitting on the nonlinear response and bistability of resonantly driven spinor exciton-polaritons in a spatially homogeneous microcavity system. Using a coupled exciton-photon mean-field model, we find that TE-TM splitting significantly modifies the bistability threshold, hysteresis width, and spin composition of the steady states. In particular, TE-TM splitting counteracts the spin imbalance imposed by elliptically polarized pumping, leading to nearly equal populations of the two spin components and strongly suppressed degree of circular polarization in the steady state. The pump momentum plays a crucial role through its connection to the curvature of the lower polariton dispersion, resulting in distinct nonlinear regimes with different switching thresholds and dynamical responses. The intermediate branch within the hysteresis loop is unstable but may exhibit slow instability growth rates, giving rise to long-lived transient states. These results clarify how TE-TM splitting reshapes bistability and nonlinear spin dynamics in polariton systems and provide insight into the controlling polariton switching behavior through cavity anisotropy and pump parameters. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Metasurface-based terahertz (THz) emitters suffer from inefficient light-matter interaction in transmissive designs. Here, we propose and numerically demonstrate a high-efficiency broadband THz emitter based on a Fano-resonant Au-SiO2-Si metasurface absorber, realizing over 80% optical absorption around 375 THz and strong field confinement. Enhanced local fields amplify the second-order nonlinear response driven by the convective acceleration of surface electrons, resulting in broadband THz generation. Furthermore, THz amplitude and bandwidth can be flexibly changed by varying the polarization angle and pulse duration. These results provide an alternative approach for the high-performance and integrated broadband THz sources based on metasurfaces.(c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Fluoride glasses, known for their ultra-wide transparency window, have been extensively studied for mid-infrared supercontinuum generation. Orbital angular momentum (OAM) modes, characterized by unique helical phase structures, have found broad applications in optical communications, particle manipulation, and optical imaging. Supercontinuum generation based on OAM modes offers the potential to significantly broaden the spectral range, enabling operation across a wider set of wavelength bands. Photonic crystal fibers (PCFs), with their high refractive index contrast due to the periodic arrangement of air holes, allow for strong confinement of OAM modes and reduced mode leakage. In this work, we propose a ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) photonic crystal fiber designed for efficient OAM-mode supercontinuum generation. By launching a pulse with 700 kW peak power and 50 fs duration at 2150 nm, we demonstrate that the OAM1,1-mode supercontinuum spectrum extends up to 5500 nm with coherence exceeding 0.99 after 3.5 cm of propagation. Furthermore, the OAM4,1 mode generates a supercontinuum spanning from 1750 to 6640 nm without requiring a significant increase in peak pump power. Compared with conventional optical fibers, the proposed ZBLAN PCF achieves broader spectral coverage with lower peak power requirements and enhanced design flexibility. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
To address the low efficiency and heavy reliance on iterative optimization in conventional metasurface design, in this work, we propose an end-to-end inverse design framework based on a self-attention enhanced CVAEtransformer. By introducing a self-attention mechanism, we construct a neural network model capable of accurately predicting the electromagnetic response of metal-insulator-metal metasurface elements, simplifying the optimization process and improving design efficiency. On this basis, a conditional variational autoencoderbased inverse retrieval model is established to rapidly generate metasurface unit structures covering a full 0-2 pi phase range at specific operating frequencies. As a proof of concept, a beam deflection metasurface is designed and simulated, and the same framework is further employed to realize a terahertz metasurface with polarization-multiplexed holographic imaging functionality. Simulation results demonstrate that the proposed method enables the end-to-end generation of structural parameters without the need for multiple iterations and successfully reconstructs distinct holographic images under y-and x-polarization states. Compared with conventional parameter-sweep-based approaches, the proposed framework significantly improves design efficiency and shortens the development cycle under given target phase distributions, providing a new approach, to our knowledge, for efficient and automated metasurface design. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
In this paper, we report a device that integrates a metasurface with a resonant cavity micro-LED. We propose a theoretical formula that extends the one-dimensional generalized Snell's law to two dimensions for constructing a novel metasurface that, to our knowledge, has not been mentioned in the existing studies. Additionally, we employed the finite difference time domain (FDTD) method for the simulation. The function of this device is to modulate the outgoing light beam at any position within two-dimensional far-field space through the metasurface, thereby providing a theoretical basis and parameter guidance for subsequent experimental research. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Mid-infrared radiation at 5.23 μm is used to probe the population-inverted 5D5/2 → 6P3/2 transition in rubidium atoms, key to widely studied frequency up-conversion scheme that produces coherent blue light. We find that resonant probe light significantly changes the optical properties of the inverted medium that exhibits high optical gain. The gain has a complex sensitivity to factors such pump laser detuning, beam alignment, and atomic density. The results are an important step towards characterizing new optical field generation in alkali atoms.
Enhancing the outcoupling efficiency (OCE) of organic light-emitting diodes (OLEDs) requires mitigating losses from surface plasmon polariton (SPP) modes. While plasmonic losses are often discussed in the context of transverse magnetic (TM) modes, our work demonstrates that the emitter's dipole orientation and the operational wavelength are more dominant factors than previously recognized. To deconvolve this interplay, we employ threedimensional finite-element method (3D-FEM) simulations to visualize the system's behavior, complemented by rigorous two-dimensional (2D-FEM) simulations that quantify plasmonic losses for TM modes across the entire visible spectrum. Our results reveal a critical spectral design paradigm: a nanostructured grating acts as a highly selective, wavelength-dependent filter. It dramatically enhances OCE for vertical dipoles, but this enhancement varies drastically across the spectrum-from up to 70 times at 400 nm to less than 10 times at 750 nm. Conversely, the grating is often detrimental to the TM-polarized component of horizontal dipole emission. This finding establishes that optimal light extraction requires a tripartite co-design of the photonic nanostructure, the emitter's dipole orientation, and the target emission wavelength. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Self-accelerating Airy-type beams exhibit rich propagation dynamics in nonlinear media, where the stability and evolution of the beam strongly depend on the nonlinear response of the medium. However, how nonlocality influences the propagation and stability of Airy-derivative beams, especially for their higher-order derivatives, still remains unexplored. Here, we numerically investigate the propagation of generalized Airy-derivative beams in local and nonlocal nonlinear media. The derivative beam breaks up into multiple solitons in local media, while nonlocality suppresses this fragmentation and promotes the formation of breathing solitons. Extending the analysis to higher-order derivative beams, we find that their stronger initial oscillations result in enhancement of transverse acceleration and peak intensities. Compared with the local media, the nonlocal response reduces the peak intensity, postpones the position of the intensity maximum, and increases the transverse displacement. These results provide further insights into the dynamics of generalized Airy-derivative beams from local to nonlocal nonlinear systems, with potential applications in all-optical routing and photonic guiding. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
We systematically investigate analytically and numerically, to the best of our knowledge, two new types (first and second) of linear and nonlinear localized defect modes (LDMs) with a narrow central peak formed in the vicinity of a single defective waveguide inside a binary waveguide array. Under specific conditions for the propagation constant of the defective waveguide, the exact solutions for linear LDMs of both types are analytically derived. In the nonlinear regime, their profiles can be numerically calculated. The linear and nonlinear LDMs of the first type are always gap states and their amplitude components bn do not have the same sign when the waveguide position n runs, whereas LDMs of the second type are always out-gap states and their amplitude components always have the same sign when n runs. The linear stability analysis shows that all nonlinear narrow-peaked LDMs are stable except for nonlinear first-type LDMs with large peak amplitude when the nonlinear coefficient is positive. We also demonstrate that both linear and nonlinear LDMs of two types can be formed or numerically calculated exactly if the propagation constant of the defective waveguide changes. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Novel synthetic cathinones pose growing challenges to drug control and public health because of their rapid structural modification, high metabolic activity, and analytical difficulty. Here, terahertz spectroscopy was used to compare the solid-state absorption spectra of (R)-, (S)-, and racemic methcathinone in the 6-20 THz range under identical experimental conditions. The two enantiomers showed highly similar overall profiles but reproducible local differences at several characteristic bands, mainly in relative intensity and band profile, which may reflect differences in the solid-state environment under the present experimental conditions. The racemate exhibited additional local spectral changes. These results indicate that terahertz spectroscopy can reveal subtle spectral differences among methcathinone chiral forms and may support rapid screening and preliminary differentiation. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
In this work, the effect of silver (Ag) nanoparticles (NPs) on the spectroscopic properties of Er3+ ions embedded in a potassium barium borate glass (KBB) matrix was systematically investigated. Glass samples were prepared using the melt-quenching technique with varying Ag concentrations. Optical absorption and emission studies revealed notable modifications in spectral features due to the surface plasmon resonance (SPR) of Ag NPs. A pronounced enhancement of Er3+ luminescence is observed after annealing of Ag containing glasses, arising from annealing-assisted Ag NPs formation and modification of the local glass environment. Fluorescence lifetime measurements further confirmed strong interactions between Er3+ ions and Ag NPs. The Judd-Ofelt (J-O) analysis was performed to assess changes in the local field environment of Er3+ ions induced by Ag incorporation. The calculated intensity parameters (522, 524, and 526) exhibited systematic variations with Ag content, indicating modifications in site symmetry and ligand field strength. The derived radiative parameters are consistent with the observed luminescence enhancement, demonstrating that Ag NPs effectively modified both emission behavior and fundamental spectroscopic characteristics of Er3+-doped potassium barium borate glasses. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
The polarization dependence of the Lamb coupling constant C between the polarization eigenmodes of a spin-VECSEL is experimentally studied. A spatial separation of 20 & micro;m between the two eigenmodes in the active medium is set up to artificially decrease C and allow a robust simultaneous oscillation of the two eigenmodes, thus making measurable a slight change of C. The value of C turns out to be polarization-dependent. Indeed, a value of C = 0.70 f 0.03 for circular polarizations versus C = 0.86 f 0.03 for linear polarizations is found, corresponding, respectively, to C = 0.97 f 0.04 and C = 1.19 f 0.04 when the two eigenmodes are superimposed in the active medium. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. https://doi.org/10.1364/JOSAB.590264
The inverse design of metamaterials involves mapping (low-dimensional) spectral responses to (high-dimensional) geometries. In this design process, a "one-to-many" mapping problem may arise (similar spectra may correspond to multiple structures). Traditional generative models such as VAEs, GANs, and DDPMs have been widely applied to inverse design problems, but often fail to ensure tight spectrum-geometry consistency and may produce complex structures that are difficult to manufacture. To address these issues, we propose a spectrum-aligned latent diffusion framework (SA-LDM), augmented with a predictive neural network (PNN) and multiple manufacturability constraints, enabling on-demand intelligent design of meta-atoms with high degrees of freedom. A multi-scale cross-attention encoder for latent encoding and a spectrum-aware conditional gated fusion module in the latent diffusion process jointly enhance alignment between generated structures and target spectra. During inference, the model leverages the PNN to rapidly evaluate candidate spectra and applies manufacturability constraints, thereby directly selecting suitable and fabricable meta-atoms from a single-pass library. Moreover, the constraint set can be flexibly tailored to the application scenario, obviating the need for complex, repetitive, and time-consuming iterative optimization. Simulation results show that SA-LDM outperforms mainstream generative models in both spectral-matching accuracy and structural simplicity. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
This JOSA B feature issue showcases cutting-edge research by participants of the 2025 Photonics North conference held in Ottawa, Canada, in May 2025. This inaugural Photonics North feature issue comprises 31 articles from researchers in Canada and abroad that cover a broad scope of optics and photonics, including quantum light-matter interaction, biophotonics, advanced imaging and sensing, green photonics and energy, high power laser technology, ultrafast optics, nonlinear optics, nanophotonics, plasmonics, semiconductor photonics, photonic materials, photonics and artificial intelligence, as well as photonic theory, design, and simulations. This introduction provides a brief history of the Photonics North conference and an overview of the articles in this feature issue. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Synthetic dimensions have emerged as a powerful framework for exploring topological phenomena beyond real space. Here, we investigate the evolution of surface modes in three-dimensional periodic crystals by introducing a synthetic translation dimension associated with unit-cell translation. By combining the surface-parallel Bloch wave vector with the cyclic translation parameter, we construct a minimal two-dimensional synthetic parameter space that fully captures boundary spectral evolution. Remarkably, this surface-mode evolution persists even when multiple bulk bands are involved, extending beyond the single-band scenarios. We demonstrate that the existence and spectral flow of surface modes are independent of microscopic details and rely only on the topology of bulk bands. Our results are validated in both three-dimensional acoustic and photonic crystal platforms, underscoring the universality of the mechanism across classical-wave systems. These findings establish synthetic translation dimensions as a general framework for predicting and controlling surface-mode evolution in three-dimensional periodic media. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Active control of circular dichroism (CD) in the terahertz (THz) band is pivotal for advancing fields such as sensing, imaging, and communications. This paper presents a tunable chiral metasurface based on the naturally occurring hyperbolic material alpha-molybdenum trioxide (alpha-MoO3) and graphene, comprising a silver (Ag) substrate, an alpha-MoO3 layer, and a top graphene layer. A periodic elliptical aperture array with a specific rotation angle is designed within the alpha-MoO3 layer to break symmetry. Following geometric parameter optimization, the metasurface achieves a CD of 0.98 at 5.47 THz, corresponding to a quality factor (Q-factor) of 162. Crucially, dynamic control of the CD response is realized by tuning the Fermi level of the graphene layer. Further analysis of the x-y cross-sectional electric field distribution at the resonance frequency reveals that the CD response originates from the structure's selective absorption of left-circularly polarized (LCP) and right-circularly polarized (RCP) light. Moreover, the metasurface exhibits excellent robustness to variations in the incident angle. This work provides what we believe to be novel insights for developing chiral biosensors and tunable polarization modulators. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Transmissive metasurfaces, as a common type of electromagnetic metasurfaces, play a significant role in regulating incident electromagnetic waves in the frequency domain. However, most previously reported transmissive metasurfaces have only a single transmission band, and even the few with two transmission bands cannot simultaneously achieve both wide-angle transmission within the transmission band and out-of-band suppression between the two transmission bands across different incident angles. To address this limitation, we propose a dual-band bandpass transmissive electromagnetic metasurface that can operate simultaneously in the Ku and Ka bands with out-of-band suppression between the two transmission bands under dual-polarized incident angles from 0 degrees to 80 degrees, which has the potential to be applied to improve the anti-interference capability of frequency-division duplexing technology and enable full utilization of millimeter-wave spectrum resources. Our proposed metasurface contains two identical honeycomb patterns printed on both sides of a dielectric substrate with a relative permittivity of 20. Compared with common substrates, this substrate has a relatively higher permittivity, which can further reduce the unit cell size of periodic structures and thereby reduce the impact of higher-order mode effects on structural performance. Within the frequency band from 5 to 40 GHz, our proposed metasurface can generate two bandpass transmission peaks around 16.3 and 34.1 GHz for dual polarizations with incident angles from 0 degrees to 80 degrees. For substrates with lower permittivity, the bandpass transmission characteristic at high frequencies cannot be obtained due to higher-order mode effects. An equivalent transmission line circuit model of this metasurface is proposed to predict and analyze the simulated transmission performance at the two transmission peaks across different incident angles. The prototype has been fabricated and measured. Measured results are in good agreement with simulated results. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
This work reports a substantial enhancement in the third-order nonlinear optical response of (Sc,V )-co-doped TiO2 thin films synthesized by using pulsed laser deposition. Comprehensive structural and chemical characterization confirms the substitutional incorporation of Sc3+ and V5+ into the rutile TiO2 lattice, accompanied by the controlled generation of Ti3+ states and oxygen vacancies. Linear optical spectroscopy reveals a bandgap widening from 3.07 to 4.08 eV with increasing co-dopant concentration, which is ascribed to the synergistic effects of the Sc3+-induced upward shift of the conduction band minimum and Burstein-Moss filling. Using the Z-scan technique with 30 ps pulses at 1064 nm, we demonstrate that co-doping simultaneously enhances the nonlinear refractive index n2 (from 3.81 to 11.43 & times; 10-14 m2/W) while suppressing the two-photon absorption coefficient beta (from 5.0 to 1.58 & times; 10-8 m/W). The resulting third-order susceptibility chi (3) reaches 1.88 & times; 10-7esu, representing a significant enhancement relative to undoped TiO2. Critically, the figure of merit values (W <^> 3.78, T <^> 0.14) satisfy the stringent performance criteria required for low-loss, high-contrast on-chip photonic switches. These findings establish (Sc,V )-co-doped TiO2 as a defect-engineered oxide platform uniquely suited for integrated nonlinear optical applications. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Volume holographic gratings are periodic refractive index structures widely used in sensing and photonic devices. This paper develops a modeling and computational framework for predicting the copying accuracy of twodimensional gratings recorded in photopolymer materials using interference lithography. A previous mathematical model is generalized to describe material transport, polymer growth, and modulation of the refractive index during exposure, enabling, for the first time, a quantitative assessment of copying accuracy in holographic gratings. High-fidelity finite-element simulations were performed for different optical lattices produced by three-beam interference. The results show that the diffusion-polymerization ratio has a strong impact on pattern accuracy, modulation depth, and polymer distribution. In particular, diffusion-dominated regimes enable high copying accuracy, while polymerization-dominated conditions lead to significant distortions of the recorded structure. Furthermore, the model predictions are experimentally validated by good agreement in the measured diffraction patterns and efficiencies.
