ABSTRACT Understanding how defect configuration and site occupancy regulate luminescence remains a critical issue in multi‐site ceramic phosphors. Herein, theSr 2 CaTeO 6 double perovskite is employed as a material system to investigate the coupled effects of Eu 3+ site‐selective substitution and Na + charge compensation. Eu 3+ ions are introduced into A (Sr 2+ )‐ and B (Ca 2+ )‐sites, while Na + ions are incorporated via homo‐site and hetero‐site compensation to construct distinct defect configurations. The results reveal that the spatial distribution of compensating ions governs the local symmetry and lattice distortion around Eu 3+ emitters. Homo‐site compensation promotes Eu 3+ ‐Na + defect pairs, resulting in enhanced local distortion and asymmetric crystal fields, whereas hetero‐site compensation redistributes the electrostatic field and stabilizes the lattice. Consequently, tunable emission behavior is achieved, with A‐site substitution exhibiting red emission while B‐site substitution shows orange emission. Moreover, hetero‐site compensation significantly enhances thermal stability, as evidenced by higher activation energies and improved emission retention at elevated temperatures. Based on these findings, a comprehensive structure‐defect‐symmetry‐optical correlation is established. This work highlights the critical role of defect spatial configuration in ceramic phosphors and provides a fundamental strategy for designing high‐performance multi‐site luminescent materials.
ABSTRACT Invisibility cloaks are evolving beyond passive scattering suppression toward the active control of radar perception. However, on‐demand generation of electromagnetic environment illusions remains challenging. Passive metasurfaces are fixed after fabrication, whereas electrically reconfigurable metasurfaces usually require dense bias networks and continuous electrical holding power, which complicate large‐aperture integration and introduce steady‐state energy consumption. Here, we report an X‐band neuro‐driven mechanically programmable metasurface (NMPM) that generates prescribed electromagnetic signatures through mechanically retained coding states. To map target scattering profiles onto implementable mechanical configurations, we develop a calibration‐assisted, physics‐guided neural programming framework. This framework compensates for coupling‐induced model mismatch and addresses the non‐unique inverse mapping from desired electromagnetic responses to discrete array states. The generated states are physically written by rotating reflective meta‐atoms optimized for linearly polarized illumination, allowing the programmed configuration to be retained without continuous electrical bias. Microwave experiments on two representative target environments demonstrate that the NMPM reproduces the dominant main‐lobe directions and overall sidelobe envelopes of the target scattering profiles. Quantitative measurements yield cosine similarities of 94%–98%, with consistent agreement under the tested incidence‐angle and frequency variations. These results demonstrate a mechanically retained and algorithmically calibrated route toward adaptive radar deception, electromagnetic scene engineering, and reconfigurable sensing architectures.
ABSTRACT Nanophotonic structures enable transformative sensing in miniaturized platforms but are fundamentally constrained by their limited sensitivity across broad refractive index (RI) ranges. Here, we developed novel “propped” plasmonic nanoparticle lattices as a universal platform for elevated high‐quality surface lattice resonances (SLRs). This architecture decouples the SLRs from the substrate, enabling effective operation in arbitrary RI environments and achieving sensitivity exceeding 1000 nm/RIU (Δn = 0.02)—surpassing the theoretical periodicity‐correlated limit. By integrating functional materials, we further validate platform versatility through proof‐of‐concept detections of (1) gas concentration by integration of metal–organic framework films with > 40 nm resonance shifts and illustrate sensitivity (∼0.8 nm/%VOL) at room temperature; (2) polymer height dynamics (resolutions at ΔH/Δλ = 24.3 nm/nm of height change/wavelength shift); (3) pH alterations (pH sensitivity up to Δλ/ΔpH = 2.8 nm/pH of wavelength shift/pH change). This work redefines the limits of RI detection and establishes a scalable and viable platform for next‐generation nanophotonic sensors across diverse applications.
ABSTRACT Pancharatnam‐Berry phase gradients generated by spatially rotated meta atoms are widely used to control optical wavefronts with metasurfaces. Here, we develop a weak measurement method for characterizing the effective Jones matrix parameters of fabricated PB phase gradient metasurfaces. In the specified effective Jones model, the local polarization response is described by the amplitude ratio and phase difference, while the spatial rotation of the meta atoms determines the PB phase gradient. By scanning the imaginary part angle and real part angle, the spin dependent deflection is converted into a two dimensional centroid map. The amplitude ratio, phase difference, and phase gradient produce different spatial features in this map, providing information for their distinction and retrieval. For a fabricated metasurface with a known phase gradient, the amplitude ratio and phase difference are obtained by fitting the measured centroid response with the theoretical model. When all three parameters are unknown, three independently trained machine learning models retrieve the amplitude ratio, phase difference, and phase gradient from the same complete centroid map and its angular coordinates. These results establish two dimensional weak measurement as an optical approach for characterizing the effective parameters of PB phase gradient metasurfaces.
ABSTRACT The polarization‐dependent diffraction efficiency inherent to liquid‐crystal spatial light modulators (SLM) is exploited to create coaxial double‐focus laser beams. The axial separation and peak‐intensity balance between the beam foci are independently controlled by actively tuning the encoded quadratic phase hologram applied to the SLM and adjusting the input laser polarization. With this and exploiting the high reflectivity of silicon, internal micro‐interactions with counterpropagating infrared pulses have become accessible by only using a single focusing element. By comparatively probing ultrafast nonlinear excitation dynamics, we show that the added angular light components and the dual‐pulse nature of the cooperative interactions under the proposed configuration, immediately lead to an enhancement of the local excitation conditions in bulk silicon. We report on the achievement of near‐critical plasma densities reaching up to , a value inaccessible by conventional focusing. This opens the door to plasma‐optics experiments and material transformations at increased energy density levels, with three‐dimensional controllability inside silicon and other narrow‐bandgap materials.
