Advanced Photonics Research最新文献

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.

Successful tuning of the metal-to-insulator transition (MIT) near room temperature for VO₂ thin films has been previously reported via a variety of methods, from strain and defect engineering to energy band restructuring. In this study, a nanocomposite VO₂ design is integrated on glass substrates resulting in tuning the transition, morphology, and optical and electrical properties. Specifically, VO₂-Au nanocomposite and VO₂ thin films are grown using pulsed laser deposition on glass with a ZnO buffer layer. The variations in film composition and buffer layer result in unique morphology, phase change properties, and optical properties. Notably, the introduction of the ZnO buffer layer results in a redshift of the surface plasmon resonance wavelength and unique epsilon-near-zero characteristic for the buffered films. Overall, this work discusses the effect on the tuning of the MIT and optical properties through a novel multifaceted approach using both defect engineering and energy band restructuring. These VO₂ and VO₂ nanocomposite films integrated on amorphous glass substrates show promise for future applications in sensing, thermochromics, and optical switching.

The scalable fabrication of high-performance nanowire (NW) photodetectors remains a critical challenge for the integration of nanoscale optoelectronics into practical technologies. This work presents a simple, rapid, and cost-effective method for the deterministic assembly of single germanium (Ge) NWs between electrode pairs using a modified dielectrophoresis (DEP) setup. By introducing a voltage-divider configuration with a series resistor, the method enables self-limiting NW alignment, eliminating the need for nanoscale electrodes or extensive pre-optimization. Devices fabricated via this approach exhibit high responsivity—exceeding 6 × 10⁵ A W⁻¹ at both 700 and 1550 nm—among the highest reported for single Ge NW photodetectors. This enhanced performance is attributed to asymmetric Schottky junctions and possible optical resonances within the NWs. The method enables the rapid production of single-NW photodetectors with tunable properties, offering a versatile platform for low-cost optoelectronic device manufacturing and advancing the feasibility of NW-based sensing, imaging, and communication technologies.

Plasmonic nanostructures can show a magnetic response in addition to an electrical one by guiding the plasmonic displacement current along a circular loop, inducing a magnetic dipole. Achieving a magnetic response at optical frequencies requires composite nanostructures with multiple elements to prevent saturation effects. A composite nanostructure consisting of three nanorods is presented that form a split-ring resonator with two additional gaps. The optical behavior of this nanostructure is investigated with both numerical simulation and experimental fabrication and measurement. Moreover, it is demonstrated that adding a nanorod below the central element facilitates an additional dark magnetic mode that causes a Fano resonance in the structure, increasing the magnetic near-field enhancement and the overall magnetic response of the nanostructure.

Intelligent characterization of van der Waals semiconductors is an essential process for industrial manufacturing and laboratory fabrication. A combination of microscopic images and artificial intelligence models is an efficient way for wafer-scale layer number identification of van der Waals semiconductors. This methodology overcomes the bottleneck of the conventional manual layer number counting approach, which requires a long period of manual inspection and induces high error rates when distinguishing layers with similar appearance. Here, a convolutional architecture that involves a fused network of ResNet-Inception with Attention Layer (RIAL) is developed for accurate multiclass classification of randomly distributed layers of chemical vapor deposition (CVD)-grown van der Waals semiconductors. RIAL model is first validated on the single-label datasets CIFAR-10/100, and subsequently fine-tuned on the custom-built microscopic image datasets of CVD-grown MoS₂. To compare with semantic segmentation, U-Net with Attention Layer (UNAL) is further implemented for pixel-wise classification of multiclass semiconductors. The quantitative analysis of RIAL and UNAL illustrates the versatility of attention convolutional network models in the wafer-scale identification of van der Waals semiconductors.

Passively phased coherent laser systems have been extensively studied for their potential to reduce design complexity in applications requiring high radiance. In this letter, the experimental demonstration of a five-element angled laser diode array coupled to a slab waveguide cavity integrated onto a single chip in a monolithic FIRE configuration is presented. Using this configuration, the common FIRE cavity performs coherent combination of the individual lasers in the array, providing high inter-element coupling and reduced edge losses to allow single supermode operation. Quasi-continuous-wave operation and high-visibility fringes in the far field (V = 98%) that demonstrate excellent coherence of the laser array are experimentally demonstrated.

Quasi-nondiffracting (QND) optical beams are well known for their long-range propagation and self-healing capabilities. Shrinking their beam width down to the mesoscale regime can open up many new applications in microtechnology, but the complexity of the beam-forming platform remains the major hindrance to its realization. In contrast, the photonic nanojets (PNJs) boast simple platforms for their generation and inherently small beam size, but their utilization has been limited mainly to near-field applications. This work aims to hybridize the QND and PNJ beam concepts, eventually realizing microscale, self-healing QND beams using a simple, PNJ-style platform. To that end, the microscale cuboids made of low-index dielectric materials are dually utilized, first to generate two self-decelerating corner-diffraction beams and then to superpose them into a long-range (10λ–100λ) microbeam. The QND–PNJ hybridization concept and model will contribute synergistically to the study and application of the microscale optical beams.

Zero-dimensional (0D) perovskite derivatives A₄PbCl₆ (A = Li, Na, K, Rb, Cs) are promising for optoelectronic applications due to their unique properties. However, synthesizing pure-phase samples is challenging, and the impact of A-site cation substitution remains less explored. Addressing these challenges, first-principles calculations based on density functional theory (DFT) are employed to investigate the electronic and optical properties of A₄PbCl₆ perovskite derivatives. The calculations reveal that the substitution of A-site cations not only modifies the lattice parameters but also alters the distribution of the local electrostatic field within the crystal. These changes lead to variations in the electron density around the Cl and A atoms, thereby tuning the electronic structure and optical properties of the system. Specifically, Cs₄PbCl₆ exhibits the highest extinction coefficient in the ultraviolet (UV) region, indicating enhanced optical activity, while K₄PbCl₆ shows greater transparency due to its lower extinction coefficient. The results not only elucidate the impact of A-site cation substitution on the properties of 0D perovskite derivatives but also provide essential theoretical insights for the rational design of new optoelectronic materials, particularly for UV detection and transparent applications.