Mode Profile Research Articles

Robust multiresonant nonlocal metasurfaces by rational design

Abstract Dielectric metasurfaces supporting optical resonances have become a promising platform for quantum and nonlinear optics. However, resonant metasurfaces remain limited in their capacity to independently control the behavior of many distinct resonances despite efforts in computational optimization and inverse design. In this work, we overcome longstanding limitations by introducing a generalized rational design paradigm based on symmetry. Specifically, we use symmetry-broken metasurfaces with periodic “quadromer” lattices comprised of four nanostructures per unit cell to enable extensive control of multiple optical resonances. The rationally designed metasurfaces are readily fabricable, and we experimentally demonstrate metasurfaces that support up to four high Q-factor resonances with deliberately chosen free-space polarizations, spectral separations, and mode profiles. Our design paradigm may unlock new applications for multiresonant metasurfaces in quantum and nonlinear optics, optical sensing, and augmented reality displays.

Predicting battery degradation profiles of IoT device usage modes through Machine Learning utilization models

Predicting battery degradation profiles of IoT device usage modes through Machine Learning utilization models

Spatiotemporal imaging of nonlinear optics in van der Waals waveguides.

Van der Waals (vdW) semiconductors have emerged as promising platforms for efficient nonlinear optical conversion, including harmonic and entangled photon generation. Although major efforts are devoted to integrating vdW materials in nanoscale waveguides for miniaturization, the realization of efficient, phase-matched conversion in these platforms remains challenging. Here, to address this challenge, we report a far-field ultrafast imaging method to track the propagation of both fundamental and harmonic waves within vdW waveguides with femtosecond and sub-50 nanometre spatiotemporal precision. We focus on light propagation in slab waveguides of rhombohedral-stacked MoS2, a vdW semiconductor with large nonlinear susceptibility. Our method allows systematic optimization of nonlinear conversion by determining the phase-matching angles, mode profiles and losses in waveguides without prior knowledge of material optical constants. Using this approach, we show that both multimode and single-mode rhombohedral-stacked MoS2 waveguides support birefringent phase matching, demonstrating the material's potential for efficient on-chip nonlinear optics.

Ultra-miniaturized Bloch mode metasplitters for one-dimensional grating waveguides.

We present, for the first time, to our knowledge, power splitters with multiple channel configurations in one-dimensional grating waveguides (1DGWs) that maintain crystal lattice-sensitive Bloch mode profiles without perturbation across all output channels, all within an ultra-miniaturized footprint of just 2.1 × 2.2 μm2. This novel capability reduces the need for transition regions, simplifies multi-channel configurations of 1DGWs, and maximizes the effective use of chip area. The pixelated metamaterial approach, integrated with a time-domain heuristic algorithm, is utilized to concurrently achieve broadband operation, optimized dispersion control, and minimal loss. We experimentally demonstrate that the 1 × 2 and 1 × 3 metasplitters achieve average minimum losses per channel of 3.80 dB and 5.36 dB, respectively, which are just 0.80 dB and 0.59 dB above ideal splitting. The measurements for both designs demonstrate a 1 dB bandwidth of 15 nm, with excellent uniformity across all output channels. These versatile metasplitter designs can serve as fundamental building blocks for ultrahigh-bandwidth, densely integrated photonic circuits and in scenarios where slow light is essential.

Cyclic Evolution of Synergized Spin and Orbital Angular Momenta.

Spin angular momentum (SAM) and orbital angular momentum (OAM)are fundamental physical characteristics described by polarization and spatial degrees of freedom, respectively. Polarization is a feature of vector fields while spatial phase gradient determines the OAM ubiquitous to any scalar field. Common wisdom treats these two degrees of freedom as independent principles to manipulate wave propagations. Here, their synergy is demonstrated. This is achieved by introducing two orthogonal p-orbitals as eigenbases, whose spatial modal features are exploited to generate OAM, and the associated orbital orientations provide means to simultaneously manipulate polarizations. Through periodic modulation and directional coupling, a full cyclic evolution of synchronized and synergized SAM-OAM is realized. Remarkably, this evolution acquires a nontrivial geometric phase, leading to its representation on a Möbius strip. Experimentally, an acoustic cavity array is designed, whose dipole resonances precisely mimic the p-orbitals, with pressure fields featuring the spatial characteristics and velocity fields the vectorial orientations. Based on this synergy, a spin-orbital-Hall effect is further showcased, highlighting the intricate locking of handedness, directionality, spin density, and spatial mode profile. This study unveils a fundamental connection between SAM and OAM, promising avenues for their novel applications in trapping, coding, and communications.

Reliable wavelength detection method of sapphire fiber Bragg gratings using added multimode fiber

Sapphire fiber Bragg gratings (SFBGs) are promising high-temperature sensors, which can be applied to measure temperature and strain in extreme environments. However, the multimode operation of SFBGs is susceptible to disturbance, leading to unreliable wavelength detection. Here, we propose by using added multimode fibers (AMMF) and tracing the longwave edge of reflection envelope to enhance the stability of wavelength detection for SFBG. The near-field profiles of transmission modes are investigated in sapphire fiber with different lengths of AMMF. It is found that the mode-field distribution of sapphire fiber can be improved by using AMMF with a length of 1000 m, which results in a reduction of relative standard deviation (RSD) from 57 % to 10 %. Then, the signal-to-noise ratio (SNR) in the reflection spectrum of SFBG is improved to 16 dB by polishing inclined end faces of sapphire fiber using the removal mechanism of hard-brittle materials. Furthermore, we detect the wavelengths of both the longwave edge and peak on the reflection envelope, which reveals lower fluctuations (i.e., SD = 0.02 nm) of the longwave edge, since lower-order modes are more stable during transmission. The effect of external disturbances (i.e., torsion and vibration) on demodulation of SFBG is also evaluated, with a maximum fluctuation of 0.06 nm (SD = 0.01 nm). A temperature experiment is carried out with the assembly and polynomial fitting curves with high fitness are obtained. Thus, our proposed methods enhance the reliability of wavelength detection in the reflection spectrum of SFBG, which is beneficial to improving the sensing performance of SFBG-based sensors.

Photonic modes in twisted graphene nanoribbons

This study investigates the behavior of photonic modes in twisted graphene nanoribbons (TGNRs) using an analytical approach based on solving the fully covariant vector boson equation. We present a model that demonstrates how helical twisting in TGNRs significantly affects the evolution of photonic modes. Our analytical solutions yield detailed expressions for mode profiles, energy spectra, and decay characteristics. We find that increasing the twist parameter shortens the decay times (τns) for damped modes, indicating enhanced photonic coupling due to the twisted geometry. Conversely, longer nanoribbons (NRs) exhibit increased decay times, showing a length (L)-dependent effect, where τns∝L/c, with c representing the speed of light. These findings may enhance the understanding of light control in nanostructures and suggest potential applications in tunable photonic devices, topological photonics, and quantum optical systems.

Double-slot micro-ring resonators with trapezoidal subwavelength grating as ultra-sensitive biochemical sensors

Silicon-based refractive index sensors are of significance in the detection of gases, biological substances and chemical compounds. Among these, optical microcavities can confine the optical field to the micrometre-scale region, and possess the advantages of high Q factor, small size and easy integration. In this paper, a trapezoidal subwavelength grating (SWG) is introduced into a slot micro-ring resonator, and the mode splitting is employed to enrich the supported standing wave modes and optimize the spatial profiles of the resonant modes. The modes’ Q factor is improved and the high sensitivity and low detection limit is achieved. The optimal trapezoidal subwavelength grating double slot micro-ring resonator (T-SWGDSMRR) structure is obtained by designing the structural parameters and analyzing their effects on the sensing performance parameters and spectral characteristics. The T-SWGDSMRR, designed for detecting the glucose solution, demonstrated a low detection limit of 3.3×10−5 RIU and an ultra-high Q factor of up to 100825, accompanied by a refractive index sensitivity of 424 nm/RIU. Finally, a cascaded double micro-ring sensor is proposed using the vernier effect, through cascading the T-SWGDSMRR with a referential ring, the sensitivity is enhanced to 12828 nm/RIU, and the limit of detection is 3.12×10−6 RIU.

Novel Insecticidal Benzo[4,5]imidazo[1,2-b]pyrazole Derivatives Identified through Ring-Closure Scaffold Hopping on Fipronil.

A series of innovative benzo[4,5]imidazo[1,2-b]pyrazole scaffold containing compounds were rationally designed through a ring-closure scaffold hopping strategy and synthetized with an intermediate derivatization approach. Physicochemical properties analysis indicated the potential pesticide-likeness of the target compounds. The optimal target compound A14 showed relatively good insecticidal activity against P. xylostella, with an LC50 value of 37.58 mg/L, and demonstrated lower acute fish toxicity compared to fipronil. Docking binding mode analysis demonstrated that compound A14 bound to GABAR through a H-bond between the amide group and the residue of 6'Thr. The differences in binding modes between benzo[4,5]imidazo[1,2-b]pyrazole target compounds and fipronil may be a key factor for the reduced insecticidal activities. The elucidated binding mode and SAR profile lay a foundation for the further structural optimization of insecticidal benzo[4,5]imidazo[1,2-b]pyrazole derivatives.

Preparation of a trans-free fat blend to substitute partially hydrogenated oil

Partially hydrogenated oil (PHO) possesses a mild flavor and exceptional processing characteristics, making it historically the primary choice for creamer. The discovery of health problems of trans fatty acids has accelerated the development of alternative fats. This study aimed to develop an optimal PHO alternative fat by physical blending. Based on the correlation between physicochemical properties and sensory attributes, soybean oil, fully hydrogenated palm kernel oil, and fully hydrogenated soybean oil (45/45/10, w/w/w) were selected to make the alternative fat. The fat blend exhibited a solid fat content (SFC) curve identical to PHO, along with similar melting crystallization behavior, crystal nucleation pattern and growth mode, viscosity (705 mPa s), and taste profile. Pearson correlation analysis was used to further clarify the correlation between properties and tastes. The result showed that the SFCs and fatty acid compositions have strong correlations with tastes. It provides a reference scheme for preparing fats with ideal tastes.

The symmetry change of the transverse modes in ring-LD end-pumped Nd:YVO[formula omitted] laser with an étalon

A straightforward method for converting the symmetry of a diode end-pumped laser with an annular pump beam has been proposed. By introducing an étalon into the cavity, we observed a change in the spatial symmetry of the transverse mode profile from rectangular to cylindrical both in degenerate and non-degenerate ranges. A simulation of the transmittance distribution of the beam through the étalon after filtering is given. Our experimental results indicate that this method of altering the symmetry maintains relative stability during the tilting of the étalon.

NetAScore: An open and extendible software for segment-scale bikeability and walkability

Systematic and reproducible analyses of walkability and bikeability are crucial for efficient and effective interventions to promote active mobility. Previous methods for segment-based walkability and bikeability are limited in applicability due to high data requirements, a constrained set of aspects considered, or are not openly available and adjustable. The lack of transparency, limited reproducibility, and the high effort required to re-implement customized and extended variants of such methods inhibit wider application and retard knowledge gain. The open source software NetAScore aims to fill this gap. It is based on open and widely available data, provides default mode profiles for modeling utilitarian bikeability and walkability, and is designed for customization. General applicability and suitability of the software and its underlying models were shown in two evaluation studies. Source code and documentation are available on GitHub and via doi.org/10.5281/zenodo.7695369.

Impact of thickness and saturation direction over magnetostatic mode energies and profiles in Ni80Fe20 antidots

Abstract The magnetization dynamics of square arrays of circular antidots fabricated on Si(001) substrates using deep ultraviolet lithography with a 248 nm exposing wavelength have been studied. The effects of thickness (40 nm and 80 nm) and the in-plane direction of the applied magnetic field on the magnetostatic mode energies were investigated through ferromagnetic resonance experiments and micromagnetic simulations for both thicknesses. The experimental results and the simulations allowed the determination of nature of the magnetostatic modes nature measured at angles of 0° and 45° between the applied magnetic field and the axis of the square array. Notably, in this geometry, the main modes do not disapear when the sample is rotated; instead, the localization of the modes follow the rotation of the applied field, with a variation in measured intensity directly related to the surface area occupied by the localized mode.

Non-Hermitian mode management in periodically modulated waveguide amplifiers

We propose an efficient mode management scheme in active nonlinear multimode fibers based on non-Hermitian potentials in the longitudinal direction with an antisymmetric transverse profile. The proposal takes advantage of the nonlinear saturation toward particular mode configurations, which can be tuned by the non-Hermitian potential. We demonstrate flexible control of the beam profile within the parameter space of the applied potential with various possibilities, such as improving the beam quality by condensing photons to the lowest order Hermite mode, exciting higher order modes, or engineering a desired mode profile as a combination of modes. The effect is also analytically predicted using a mode-expansion approach, showing good agreement with the full model calculations based on the complex Ginzburg–Landau equation. This study was performed for 1D planar guiding structures, yet the results can be extended to 2D fibers and could be very useful in applications of fiber amplifiers and lasers.

High responsivity zero-biased Mid-IR graphene photodetector based on chalcogenide glass waveguide

Graphene’s unique properties have made it a promising material for high-performance photodetectors due to its interesting features including broadband absorption, fast speed, and strong photothermoelectric effect. Here, an optimized waveguide photodetector incorporating double graphene layers with two cores is presented to boost the responsivity (∼twice), at Mid-IR range. The proposed structure operates in the zero-bias regime to eliminate the dark current issue associated with the zero bandgap nature of graphene and leads to lower noise equivalent power. The presented photodetector operating based on split gates to electrostatically induce the p-n junction in graphene channels, operates based on the photothermoelectric effect and provides responsivity, NEP, and 3 dB bandwidth of 6.3 V/W, 0.34 nW/Hz1/2, and 1.54 GHz, respectively for the detection at λ = 5.2 μm. The feasibility of the proposed structure is proved according to recent experimentally demonstrated photodetectors. Hence, the obtained results are reliable, in practice. The study has been accomplished by numerical simulation of mode profiles and solving the heat equation to extract the characteristics of the proposed photodetector. The zero-power consumption and tunability of the proposed structure make it a promising candidate for sensing, industrial, defense, and environmental monitoring applications with high accuracy.

Resonant Metasurfaces with Van Der Waals Hyperbolic Nanoantennas and Extreme Light Confinement

This work reports on a metasurface based on optical nanoantennas made of van der Waals material hexagonal boron nitride. The optical nanoantenna made of hyperbolic material was shown to support strong localized resonant modes stemming from the propagating high-k waves in the hyperbolic material. An analytical approach was used to determine the mode profile and type of cuboid nanoantenna resonances. An electric quadrupolar mode was demonstrated to be associated with a resonant magnetic response of the nanoantenna, which resembles the induction of resonant magnetic modes in high-refractive-index nanoantennas. The analytical model accurately predicts the modes of cuboid nanoantennas due to the strong boundary reflections of the high-k waves, a capability that does not extend to plasmonic or high-refractive-index nanoantennas, where the imperfect reflection and leakage of the mode from the cavity complicate the analysis. In the reported metasurface, excitations of the multipolar resonant modes are accompanied by directional scattering and a decrease in the metasurface reflectance to zero, which is manifested as the resonant Kerker effect. Van der Waals nanoantennas are envisioned to support localized resonances and can become an important functional element of metasurfaces and transdimensional photonic components. By designing efficient subwavelength scatterers with high-quality-factor resonances, this work demonstrates that this type of nanoantenna made of naturally occurring hyperbolic material is a viable substitute for plasmonic and all-dielectric nanoantennas in developing ultra-compact photonic components.

Dynamical phase-field model of cavity electromagnonic systems

Cavity electromagnonic system, which simultaneously consists of cavities for photons, magnons (quanta of spin waves), and acoustic phonons, provides an exciting platform to achieve coherent energy transduction among different physical systems down to single quantum level. Here we report a dynamical phase-field model that allows simulating the coupled dynamics of the electromagnetic waves, magnetization, and strain in 3D multiphase systems. As examples of application, we computationally demonstrate the excitation of hybrid magnon-photon modes (magnon polaritons), Floquet-induced magnonic Aulter-Townes splitting, dynamical energy exchange (Rabi oscillation) and relative phase control (Ramsey interference) between the two magnon polariton modes. The simulation results are consistent with analytical calculations based on Floquet Hamiltonian theory. Simulations are also performed to design a cavity electro-magno-mechanical system that enables the triple phonon-magnon-photon resonance, where the resonant excitation of a chiral, fundamental (n = 1) transverse acoustic phonon mode by magnon polaritons is demonstrated. With the capability to predict coupling strength, dissipation rates, and temporal evolution of photon/magnon/phonon mode profiles using fundamental materials parameters as the inputs, the present dynamical phase-field model represents a valuable computational tool to guide the fabrication of the cavity electromagnonic system and the design of operating conditions for applications in quantum sensing, transduction, and communication.

A potential algicidal bacterium against Spirogyra gracilis blooms: identification, algicidal activity, algicidal mode, and metabolomic profiling

A potential algicidal bacterium against Spirogyra gracilis blooms: identification, algicidal activity, algicidal mode, and metabolomic profiling

Watt-level cladding-pumped bismuth-doped fiber laser operating near 1.31 [formula omitted]m

We report, to the best of our knowledge, the first CW bismuth-doped fiber laser operating at around 1.31 μm with an output power of >1 W utilizing a cladding-pumping configuration with multimode semiconductor laser diodes emitting at a wavelength of 793 nm. The Bi-doped fiber (BDF) serving as an active medium of the laser was based on a pedestal-index design, where P2O5−SiO2 glass core surrounded by P-doped cladding. The BDF construction offers advanced gain characteristics and an increased mode size (∼13 μm). The fiber preform was fabricated by the conventional modified chemical vapor deposition (MCVD) method combined with all gas-phase doping technique. The BDF with low-index polymer coating provided sufficient cladding peak absorption at 750 nm belonging to bismuth active centers associated with phosphorus atoms (BACs-P) that allowed to develop a continuous-wave laser with a linear cavity configuration and enable a maximum slope efficiency of ∼ 4% with respect to the absorbed pump power. In addition, near-field spatial intensity distribution of optical beam has good quality (M2<1.13) and close to Gaussian mode profile in x and y directions. The perspectives for optimization of BDF design and laser system configurations based on such fibers for further power scaling are discussed.

A person-centered, transdiagnostic schema and mode profile approach to predict outcome in time-limited schema group therapy

Objective This study employs a person-centered transdiagnostic approach to examine how schema and mode profiles predict symptom severity reduction in schema group therapy for patients with personality disorders and enduring clinical syndromes. Method We analyzed symptom reduction in 248 patients across three formats of manualized, time-limited schema group therapy. Latent profile analysis and mixed multilevel modeling were used to determine the extent to which schema/mode classes predict symptom reduction, and whether the inclusion of individual schemas and modes enhances these predictions. Results No significant differences in treatment outcomes were found across the group modalities. A three latent profile solution for schemas and modes showed external validity with clinical variables and demonstrated that declines in symptom severity varied by schema and mode class, even after adjusting for baseline symptom severity. Adding the Vulnerability to Harm schema and Vulnerable Child mode to the model increased the explained variance. Conclusion Patients with more severe personality problems show more substantial symptom reduction. Both schema and mode profiles significantly contribute to predicting post-treatment symptom levels. Understanding these profiles may help therapists tailor interventions more effectively, consistent with Young’s theoretical model. Trial registration: ISRCTN.org identifier: ISRCTN17262253.