Advanced Photonics Research最新文献

Capacitive Mems Actuator Arrays

In their Research Article (10.1002/adpr.202500228), Van Minh Nguyen, Yoshiaki Kanamori, and co-workers present a SSPP waveguide integrated with SRR metamaterial and MEMS actuator arrays with electric field confinement in the gap below the micro-bridge. The notch-band in the microwave transmission characteristic shifts due to the micro-bridge’s deflection leading to a phase shift of the guided microwave.

Persistent luminescent materials are essential for advancing energy-efficient lighting, bioimaging, and sensing technologies. However, improving their optical performance remains a key challenge. Here, the integrating of Ag and Au plasmonic nanoparticles (NPs) on the surface of consolidated SrAl₂O₄:Eu²⁺,Dy³⁺ ceramics enhances both photoluminescence intensity and the persistent afterglow through increasing the light concentration and charge transfer between the NPs and the luminescent matrix. The ceramics are sintered via hot isostatic pressing, achieving >99% theoretical density with controlled surface roughness optimized for nanoparticle deposition. Functionalization of plasmonic nanostructures is achieved through solid-state dewetting of thin metallic films followed by thermal annealing. This process generates discrete NPs with strong localized surface plasmon resonances. Finite element simulations reveal a hole-sphere-like growth for plasmonic NPs after the solid-state dewetting process, as well as a stronger local electric field enhancement around NPs at the excitation wavelength, correlating with experimental results. This work demonstrates an effective route for tailoring long-persistent phosphors and offers new perspectives for the design of advanced optoelectronic materials.

Energy transfer between a donor-acceptor pair of J-aggregated dyes, which are spin-coated onto the mirrors of a tunable Fabry–Pérot microresonator, is studied. It is found that both donor and acceptor are strongly coupled to the optical modes of the resonator and form hybrid light–matter states (polaritons). The shapes of the fluorescence spectra show efficient energy transfer from donor to acceptor, which are separated up to 11 μm. Within the same measurement, the energy transfer efficiency appears to be independent of donor–acceptor separation. The observed fluorescence features are well explained by a phenomenological Hamiltonian, which models the emerging polariton modes and rate equations.

Electron injection stability is crucial for organic semiconductors. Although phenanthroline (Phen) derivatives are stable and efficient electrode modification materials, their air stability is underexplored, and the impacts of environmental factors on Phen-modified electrodes are not well understood. This study investigates the degradation of Phen-modified organic light-emitting diodes (OLEDs) by monitoring temporal changes in the light-emitting area under ambient air exposure without encapsulation. The results demonstrate that Phen modification stabilizes electron injection under room-temperature and atmospheric-pressure conditions. The degradation behavior is consistent with Fick's law of diffusion. A strong correlation between the degradation rate and relative humidity indicates a mechanism wherein water molecule diffusion governs the degradation process. The film densities of Phen derivatives are calculated using molecular dynamics simulations. High-density modifier films may physically hinder water diffusion, suppressing degradation. These findings highlight the potential of Phen-based materials to enable high-performance organic electronics with efficient electron injection and enhanced stability under minimal encapsulation.

Ultrabroadband absorption across the long-wave and ultralong-wave infrared (LWIR/ULWIR) spectrum is essential for applications ranging from thermal imaging to spectroscopy, yet remains a persistent challenge. Herein, a refractory metamaterial absorber (MMA) composed of four vertically tapered silicon nitride (Si₃N₄) rods on a tungsten substrate is proposed. Finite element method (FEM) simulations show that the MMA achieves an absorbance of over 90% from 7.15 to 31.62 μm, with a relative bandwidth of 126.23%. Notably, the absorbance peak of the MMA is up to 99.97%, 97.92%, 98.42%, and 99.96% at 7.653, 9.045, 16.762, and 26.731 μm, respectively. An equivalent circuit model corroborates these results and elucidates the underlying impedance matching. The ultra-broadband performance arises from synergistic coupling of multiple resonant modes, including waveguide resonance (WGR) with higher-order, Fabry–Pérot (F–P) cavity resonance (FPCR), local surface/propagating plasmon resonance (LSPR/PPR), as well as intrinsic losses of Si₃N₄ material. The MMA also exhibits wide-angle stability, maintaining high efficiency for incidence up to 50° under both TE and TM polarizations. It's simple, tunable geometry and fully dielectric composition facilitate fabrication and ensure high-temperature resilience. This design offers a robust platform for advanced infrared systems, including thermal energy harvesting and spectral imaging.

Nonlinear optical materials designed for mid-infrared applications gain increasing interest in photonics and quantum-optical research. However, many of these materials remain unexplored in the broad mid-infrared range due to the limited availability of suitable equipment. Silver thiogallate (AgGaS₂) is one of the widely known nonlinear crystals used in mid-infrared frequency-conversion applications. While its transmission and refractive indices are well characterized up to 10.6 μm, dispersion properties beyond this wavelength remain unreported. In this work, a quantum-optical approach is employed to determine the refractive indices of AgGaS₂ across an extended mid-infrared wavelength range. Correlated photon pairs are generated in the crystal, where one photon in a pair is generated at a near-infrared wavelength and the other in the mid-infrared. Due to the correlations, detecting the spectrum of the near-infrared photons allows inferring the crystal's dispersion properties in the mid-infrared region up to 21 μm, without the need for infrared light sources or detectors. Sellmeier equations are further proposed that accurately describe both ordinary and extraordinary refractive indices across the entire transparency range of the crystal. The results are consistent with previously reported data below 10 μm and demonstrate the suitability of AgGaS₂ for frequency-conversion processes over an extended wavelength range.

Herein nonlocal metasurfaces of parallel bars stitched to cubic rectangles containing structural and symmetry perturbations with a coupling of localized Mie resonance in meta-atoms and Bragg modes in photonic crystals are reported. Two Fano resonances have been identified that maintain ultrahigh Q-factors at incident angles of light up to 5°. Increasing the symmetry of the meta-atoms results in Fano resonances with Q-factors increased by a factor of 26, compared with the metasurfaces with a single bar stitched to a cubic rectangle at the incident angle of 5°. Due to nonlocal coupling of Bragg scattering and Mie resonance, the Q-factor maintains almost a constant at 5° of incidence, while it varies with structural or symmetrical perturbations at 0°.

Metasurfaces have emerged as an ultrathin, versatile method for manipulating terahertz surface plasma waves that are critical for subwavelength optical control but are very challenging to be excited and characterized. This review presents recent advances in terahertz surface plasmon waves, focusing on three functional areas: excitation through resonant coupling, beam shaping through phase gradient design, and complex field encoding using metaholography. To validate and analyze these phenomena, near-field scanning terahertz microscopy (NSTM) is recently developed as a powerful tool for mapping the field distribution of surface plasmon waves, spin- and polarization-sensitive responses, and vector wavefront structures with subwavelength resolution. Representative metasurfaces architectures are highlighted, including periodic and nonperiodic resonators, dynamic phase modulators, and multiplexed holographic encoders, and summarize how their performance can be directly observed through the NSTM platform. Together, these studies demonstrate the synergy between metasurfaces design and near-field characterization. The integration of reconfigurable metasurfaces with an advanced near-field scanning platform will be key to realizing high-capacity, tunable terahertz photonic devices.

A symmetry-protected bound states in the continuum (BIC) mechanism based on borophene metamaterials, achieving broadband coherent perfect absorption (CPA) with dual-band absorption peaks in the near-infrared waveband, is proposed. Through coupled mode theory analysis incorporating near-field and far-field coupling effects, structural parameter optimization enables synchronized strong critical coupling states for both absorption bands. Benefiting from weak angular dispersion induced by the flat-band characteristics of deep subwavelength periodic structures, the system demonstrates high stability in absorption efficiency and resonant wavelengths under wide-angle incidence (within 60°). Under coherent beam excitation, the system not only achieves CPA states but also realizes absorption switching functionality via precise control of the inter-beam phase difference. Notably, dynamic carrier density modulation significantly broadens the CPA operational bandwidth, effectively overcoming the narrowband limitations inherent to conventional CPA systems. This study establishes a novel theoretical framework and implementation strategy for advancing multifunctional tunable absorbers and all-optically controlled devices.

Hyperspectral imaging in the visible spectrum offers significant potential for diverse applications, but is often constrained by bulky hardware and limited robustness in low-light conditions. To overcome these challenges, a simulation-based proof-of-concept for a metasurface-encoded single-pixel hyperspectral imaging system (MESH) is presented, in which structured spatial modulation is combined with a compact set of 50 broadband metasurface filters designed using a binary pattern generation strategy to ensure low interfilter correlation. Hyperspectral datacubes comprising 301 channels from 400 to 700 nm are reconstructed via a sparsity-constrained optimization algorithm, while a physics-enhanced deep learning model is further introduced to enable fast and accurate recovery. Simulation results demonstrate that MESH achieves a spectral resolution of 1.17 nm. Even at a total compression ratio of 2.1%, the deep learning model maintains high reconstruction quality, with a peak signal-to-noise ratio of 30.96 dB, structural similarity of 0.8526, and spectral angle mapping of 0.0742 rad, indicating accurate intensity recovery, structural preservation, and spectral integrity. The present study provides a simulation-based verification of feasibility and design guidelines, laying the groundwork for future experimental validation of the MESH system, which is expected to further demonstrate its practical applicability and performance for deployment in low-light and resource-constrained environments.