Advanced Photonics Research最新文献

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.

Using glancing angle deposition (GLAD), this study fabricated chiral zirconium nitride structures with triangular and L-shaped geometries on quartz substrates with thicknesses between 172 and 344 nm. Some films are sputtered at room temperature while others were heated to 300 °C during deposition. Circular dichroism (CD) spectroscopy confirmed optical chirality in all GLAD fabricated films, with clockwise and counterclockwise deposited films exhibiting mirror image CD spectra. A single peak around 280 nm is observed for all films deposited at glancing incidence. Additionally, increasing the deposition time per triangular side redshifts the CD peak, demonstrating tunability of the optical response. X-ray diffraction reveals that heating induces crystallinity into the films with a Zr₃N₄ (011) peak at 28.5°, Zr₃N₄ (111) peak at 30.6°, and a ZrN (200) peak at 39.8°. SEM confirms tilted columnar growth in both heated and unheated films. Finite element simulations using COMSOL Multiphysics reproduce the main CD features, including a strong peak at ≈280 nm.

Micro-electro-mechanical system (MEMS) actuator arrays integrated into the gap of split-ring resonators (SRRs) that are capacitively coupled to a spoof-surface-plasmon-polariton (SSPP) waveguide are numerically designed and experimentally fabricated. Owing to its compact size and lightweight structure, the microbridge exhibits high-speed operation with a mechanical resonant frequency of 1.505 MHz in air. The microbridges are capacitively actuated by embedded lead electrodes and grounded microbridge arrays. When an alternating current (ac) voltage V_ac of 30 V is applied, a maximum phase shift of 2.55° is achieved at 6.65 GHz, whereas a direct current (dc) voltage V_dc of 140 V results in a maximum phase shift of 2.96° at 7.95 GHz. Theoretical analysis and numerical simulations reveal that the voltage-induced deformation of the microbridge alters the dispersion properties of the SSPP waveguide and perturbs the local electric field beneath the bridge, thereby enabling phase modulation of the guided microwave signal. These findings demonstrate the capability of the device to function as an active phase modulator for integrated microwave circuits, with potential applications in 5 G/6 G communication systems and time-varying metamaterials.

The growing demand for advanced data storage and signal processing technologies has intensified the search for novel materials with tunable optical and electronic properties. Chiral 2D perovskites have emerged as promising candidates due to their unique ability to selectively absorb and emit circularly polarized light, as well as to interact with polarizable currents. To exploit these properties in applications, chiral 2D perovskites should be integrated as thin films in various device architectures, yet the means to control their crystallization and film formation processes remain underdeveloped. This study demonstrates that additive engineering can be applied to control the microstructure and strain in chiral 2D perovskite thin films. It is shown that the addition of small amounts of hypophosphorous acid to the precursor solution of (R-3BrPEA)₂PbI₄ chiral perovskites results in the dissolution of colloids, leading to a significant increase in the grain size and a release of lattice strain. Consequently, the intensity of their photoluminescence is significantly enhanced, demonstrating that grain boundaries and strain lead to nonradiative recombination losses in chiral 2D perovskites. The findings motivate the exploration of novel additive engineering approaches to improve the optoelectronic quality of chiral 2D perovskite thin films.

Terahertz (THz) metamaterial absorbers (MAs) exhibit significant potential in imaging, communication, sensing, and energy harvesting. For these applications, achieving broadband absorption within an ultrathin profile is crucial. However, realizing this objective while preserving high performance remains a key challenge. In this work, a compact THz MA based on a four-lobed fan-shaped corrugated structure supporting spoof localized surface plasmons is presented. The design of the four-lobed structure facilitates multiresonance coupling, while the use of indium tin oxide for both the patterned structure and ground plane introduces ohmic loss. The proposed design achieves over 90% absorption from 0.75 to 2.16 THz, corresponding to a relative bandwidth of 97%, with a thickness of only 25 μm (relative thickness of 0.067$��{\lambda }_L�$, where $��{\lambda }_L�$ is the wavelength at 0.75 THz). The absorber maintains stable performance for both transverse electric and transverse magnetic (TM) polarizations under oblique incidence angles up to ±60°, indicating strong angular and polarization robustness. These results may stimulate further advancements in the development of compact and optically transparent absorbers that combine broadband operation with minimal thickness, thereby enabling new possibilities for practical THz devices.