Advanced Photonics Research最新文献

Hermite–Gaussian (HG) modes are an orthogonal set of solutions to the paraxial wave equation possessing distinct spatial intensity variations, which are important in many optical applications. Here, anisotropic second- and third-harmonic HG beam generation is demonstrated with ultrathin niobium oxide diiodide (NbOI₂) grating holograms to produce the nonlinear HG₀₁ and HG₁₀ modes. It is shown that the generated second-harmonic HG modes exhibit a high anisotropy ratio reaching a large value of 14.95, while the simultaneously generated third-harmonic HG modes have an anisotropy ratio up to 4.85. The relative magnitudes of the second- and third-order nonlinear susceptibility tensor elements of NbOI₂ crystal are extracted by analyzing the polarization-dependent nonlinear emission. These demonstrations provide new opportunities for building functional polarization-sensitive nonlinear optical devices used for future integrated photonic chips, optical computing, and optical communication.

Metasurfaces offer precise manipulation of light through engineered subwavelength nanostructures. However, metalenses are challenging to design such that they simultaneously achieve wide field of view (WFOV), achromatic focusing at red (R), green (G), and blue (B), and high numerical aperture (NA). Here, an RGB-achromatic bilayer metalens capable of wide-angle imaging with a field of view of 80° and a NA of 0.65 is proposed. Utilizing silicon nitride bilayer meta-atoms, the metalens maintains consistent focal lengths across RGB even at oblique incident angles up to 40°. Simulation results verify superior achromatic focusing and reduced coma aberration compared to conventional hyperbolic metalenses. This approach significantly enhances practical applicability of metalenses in digital imaging and display systems.

The rapid advancement in optoelectronic devices has sparked intense interest in wide-bandgap semiconductors for UV and X-ray detection. While Ga₂O₃ has emerged as a promising material for photodetection, a quantitative understanding of the relationships between material properties, device structures, and detection performance remains challenging. This analysis reveals that among different types of UV photodetectors, phototransistors and avalanche devices can achieve superior responsivity (up to 10⁷ A W⁻¹) and detectivity (up to 10¹⁸ Jones), while for X-ray detection, structures based on Ga₂O₃-derived materials demonstrate the highest sensitivity (up to 10⁹ μC Gy_air⁻¹ cm⁻²). Insights into their gain mechanisms and performance characteristics for various X-ray detectors, especially with heterojunction and cold cathode designs are provided. In summary, this systematic comparison of growth conditions, device structures, and detection capabilities provides a valuable reference for future developments in Ga₂O₃-based UV and X-ray detection systems.

Lanthanide-activated CsPbX₃ perovskites (Ln³⁺:CsPbCl₃) hold immense promise for the development of next-generation solid-state lasers. Realizing their full potential hinges on achieving controlled lanthanide concentrations with homogenous distribution throughout the perovskite host—a considerable material processing challenge that hinders widespread application. This work introduces a robust, scalable mechanochemical synthesis for producing both singly doped Ln³⁺:CsPbCl₃ (Ln³⁺ = Pr³⁺, Nd³⁺, Ho³⁺, Er³⁺, Yb³⁺) as well as co-doped Ln^3+(I)/Ln^3+(II):CsPbCl₃ (Ln^3+(I)/Ln^3+(II) = Nd³⁺/Yb³⁺, Ho³⁺/Pr³⁺, Er³⁺/Pr³⁺) microcrystalline powders. Complementary structural characterization techniques (e.g., X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and X-ray fluorescence) directly quantify doping concentration and confirm homogeneous Ln³⁺ distribution throughout the powders. Detailed photoluminescence (PL), PL excitation, and PL lifetime measurements reveal distinct emissive and absorptive states in the visible to short-wave infrared (IR) stemming from the dopants. Melt-grown crystals, derived from mechanochemically prepared powders, exhibit enhanced PL lifetimes compared to their source powders and are transparent at IR emission wavelengths. Overall, this mechanochemical approach allows for considerable control over dopant incorporation, yielding powders that are well-suited for the melt-growth of rare-earth-doped single crystals and the future development of halide perovskite-based solid-state lasers.

Due to their remarkable performance and exceptional color purity, the multiresonance thermally activated delayed fluorescent (MR-TADF) materials are prioritized in the research of narrowband organic light-emitting diodes (OLEDs). However, the atomic numbers of elements such as carbon (C), boron (B), and nitrogen (N) used for B–N-based MR-TADF system are relatively small, which offers limited spin-orbit coupling (SOC) strength. Furthermore, the singular short-range charge-transfer (SRCT) characteristics of MR-TADF emitters also result in the small SOC matrix elements between singlet and triplet excited states. Both lead to a slow reverse intersystem crossing (RISC) process, which constrains their further development in OLED devices. This review focuses on the molecular design strategies aimed at enhancing the SOC, including heavy atom and long-range charge-transfer (LRCT) strategies, with the objective of systematizing knowledge in this domain to facilitate the prosperous development of MR-TADF emitters with high RISC rates. Finally, the challenges and prospects in this area are discussed comprehensively at the end of the review.

Poly(ethylene terephthalate) (PET) films are widely used in flexible electronics and optoelectronics, where mechanical durability and optical performance under strain are essential for device reliability. This study investigates the effects of cold-drawing amorphous PET under ambient conditions on its optical and molecular characteristics, using ultraviolet–visible (UV–Vis) and Raman spectroscopy. It examines how varying strain levels, from 0% (unstretched) to 30%, affect transparency, vibrational modes, and molecular reorganization. UV–Vis absorbance measurements, performed ex-situ after strain release, reveal persistent changes in light transmission, including up to 100% increased absorption in the UVA and visible regions, particularly following large deformations. Raman spectra show that strains above 5% cause irreversible shifts in vibrational lines and increased full width at half maximum (FWHM). These spectral changes suggest partial molecular reorientation and emerging structural order, consistent with prior reports on cold-drawn amorphous PET. The phonon mode coupled with C-O stretching [O-CH₂] shows the strongest response to mechanical stress. This work provides insight into strain-induced optical and structural changes in PET, informing strategies to improve the performance of PET-based devices in strain-sensitive applications such as organic solar cells (OSCs), organic light-emitting diodes (OLEDs), and flexible sensors.

Liang Wu, Xi Zhang, Yi Fu, Kai Kang, Xin Ding, Jianquan Yao, Zhiyong Wang, Jiaguang Han, Weili Zhang, Adv. Photonics Res. 2022, 3, 2200033, https://doi.org/10.1002/adpr.202200033

The published version lacks acknowledgment of the core funding from: This research was funded by the National Natural Science Foundation of China (61735010, U2230114), and the National Key Research and Development Program of China (2022YFA1203502, 2017YFA0700202).

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Perfect Absorption

Interferenceless perfect absorption holds significant potential for applications in photodetection, photovoltaics, and medical diagnostics. In article number 2400187, Yibin Tian, Rujiang Li, and co-workers present an innovative composite metamaterial made of hexagonal boron nitride and lithium fluoride layers. The proposed design achieves broadband interferenceless perfect absorption, independent of the polarization of the incident light field, and across a wide range of incident angles.

The 5-year survival rate for pancreatic cancer remains below 10%, primarily due to challenges in early diagnosis stemming from the pancreas’ deep anatomical location, nonspecific early symptoms, and limited sensitivity of current diagnostic methods. Conventional serum biomarkers like carbohydrate antigen 125, carbohydrate antigen 199, and carcinoembryonic antigen exhibit minimal expression during early disease stages, rendering standard assays inadequate for trace quantification and prone to high false-negative rates. This study presents a groundbreaking toroidal terahertz (THz) metasurface biosensor designed to transform biomarker detection. Leveraging gold nanoparticles (AuNPs) to amplify THz signals, the platform achieves enhanced sensitivity through antigen-AuNPs composite probes and optimized surface functionalization that maximizes antibody immobilization while minimizing nonspecific binding. Computational simulations demonstrate a sensitivity of 97.6 GHz/RIU (refractive index unit). Experimental validation reveals distinct frequency shifts for three pancreatic cancer biomarkers within the clinically critical 1–1000 pg mL⁻¹ range, accompanied by linear dose–response relationships. This ultrasensitive biosensor overcomes longstanding barriers in detecting early-stage pancreatic cancer markers, enabling precise ultra-low concentration quantification, a transformative advancement for early screening and dynamic treatment monitoring.

The second-harmonic generation (SHG) susceptibilities of few-layer SnSe with ferroelectric stacking are investigated using both experimental and theoretical approaches. Theoretical calculations predict a maximum bulk SHG susceptibility of 2444 pm V⁻¹ at 1.2 eV, which is three orders of magnitude larger than that of typical nonlinear crystals. Experimentally, a maximum value of 1424 pm V⁻¹ at 1.19 eV in close agreement with the theoretical prediction is measured. The anisotropic SHG patterns observed experimentally align with theoretical predictions based on the material's point group symmetry. The photon-energy dependence of SHG patterns is also measured within the range of 1.19 to 1.55 eV to explore the relative strengths of various SHG susceptibilities. Notably, the measured $��{\chi }_{�y�y�y�}^{��\left(�2�\right)��}�$ is significantly larger than the theoretical value of bulk AC-SnSe, likely due to the strain effects and the mixing of ferroelectric and antiferroelectric stacking configurations in the practical SnSe few-layer samples.