Optics letters最新文献

Here, we report the group theory-based inverse design of meta-atoms for a dielectric metasurface in GaAs with predictable optical linear response and third harmonic generation (THG). Six sharp Fano resonances have been observed with a corresponding polarization dependence as predicted by group theory and the meta-atom's symmetry in the D_2h point group. THG has been observed for two modes under x-polarization excitation and one mode for y-polarization, in agreement with theoretical symmetry predictions. The polarization-dependent THG aspect ratio was observed to reach as high as 10⁸. Through strategic structural or symmetry-preserving perturbations, it was shown that the THG can be enhanced or reduced by a factor of 7. The highest THG conversion efficiency was estimated to be 3.1 × 10^-7 at the pump intensity of 1.51 MW/cm². This high THG conversion efficiency indicates that our group theory approach to modal engineering opens a new path, to the best of our knowledge, toward optical nonlinearity tuning in dielectric metasurfaces.

Copper (I) thiocyanate (CuSCN) is a highly promising hole-injection layer (HIL) for optoelectronic devices due to its excellent hole mobility, optical transparency, and solution-processability. However, challenges related to defect states and film quality persist. This study presents a simple strategy for air-induced surface chemical restructuring of CuSCN films, effectively reducing surface defects and increasing covalent character. Results show that quantum-dot light-emitting diodes (QLEDs) fabricated with air-processed CuSCN HIL demonstrate approximately two-fold improvements in both brightness and efficiency compared to devices made in nitrogen atmospheres. These findings offer valuable insights for the development of cost-effective, high-brightness QLEDs, applicable across various transport layer systems.

The ability to shape materials into precise three-dimensional geometries is crucial for advanced light-emitting functional devices. While laser nanoprinting enables the fabrication of custom 3D nanostructures, its reliance on two-photon polymerization (TPP) typically demands photoinitiators. This requirement complicates the integration of luminescent units, as their compatibility with the photoinitiators must be carefully managed. Herein, we introduce an aggregation-induced emission (AIE)-dye resin, in which the AIE dye serves a dual role as photoinitiator and emissive unit, enabling direct printing of arbitrary 3D nanostructures. This approach bypasses the traditional compromise between high-resolution patterning and luminescence performance.

We propose a scheme based on synthetic-flux-induced topological edge modes for realizing Hong-Ou-Mandel (HOM) interference between spatial polarization modes in a long-period grating waveguide. By engineering the relative modulation phase of the gratings, a tunable synthetic magnetic flux is generated, enabling controlled conversion between the TE and TM modes and forming an effective mode lattice. At a flux of π, the coupled-waveguide system supports compact, highly localized topological edge modes. Harnessing these boundary states, we achieve HOM interference with near-unity visibility that is insensitive to propagation distance and robust against variations of the coupling coefficients. These results may provide a route for fault-tolerant on-chip photonic quantum circuits.

We report on the development of a packaged optical whispering-gallery-mode (WGM) resonator exhibiting low vibration sensitivity. The fractional frequency shift is measured to be on the order of 10^-10/g along the vertical axis and 10^-11/g along the horizontal axis. The resonator, operating in the optical domain with an intrinsic quality factor of Q∼10⁹, is employed for laser frequency stabilization. The resulting laser exhibited a relative frequency stability 3×10^-12 level at 10 ms integration time. These results highlight the potential of optical WGM resonators as compact, mechanically robust frequency references for precision photonic systems.

On-chip photonic systems are essential for next-generation information processing, where multi-way beam splitting can significantly enhance parallelism and processing capacity. Conventional splitters suffer from polarization and wavelength dependence, limited integration density, and poor uniformity. Here, we develop a femtosecond-laser-based quasi-parallel scanning technique to fabricate 3D multi-way splitters with high uniformity (up to 92.62%) and broad bandwidth (750-1050 nm). This approach offers a promising solution for future optical computing, sensing, on-chip communication, and quantum photonic systems.

Understanding the three-dimensional organization of brain microstructure is essential for revealing the functional relationships between neurons and glial cells. We have constructed a Fourier Light Field Fluorescence Polarization Microscopy (FLF-FPM) system that can reconstruct the volumetric distribution of six Stokes-derived polarization parameters, enabling scan-less three-dimensional tomographic imaging of fluorescence intensity and polarization. Applied to ex-vivo mouse brain samples stained with GFP, NeuN, and Iba1, the system reveals distinct depth-dependent polarization signatures for each fluorophore label, reflecting both their intrinsic emission characteristics and tissue scattering effects. FLF-FPM provides a compact, low-cost, and quantitative approach for characterizing cellular morphology, layer-specific organization, and local optical anisotropy in thick brain tissue, offering a new, to the best of our knowledge, platform for investigating the structural basis of neural function.

A femtosecond optical parametric oscillator (fs-OPO) based on type-I (o→e + e) noncollinear phase matching in the yz plane of bismuth triborate (BIBO) crystal is demonstrated, which breaks the bandwidth (700-1900 nm) limit set by collinear phase matching. The pumping source is provided by the second-harmonic (SH, 520 nm) wave of a homemade 1040-nm Yb:fiber femtosecond laser with a pulse duration of 177 fs and a repetition rate of 100 MHz. Experimentally, the wavelengths can be tuned from 626 nm to 3051 nm (626-1026 nm for signal and 1067-3051 nm for idler) by adjusting the angle of the BIBO crystal, which, to the best of our knowledge, is the widest wavelength tuning range for any BIBO-based femtosecond OPO. At the wavelength of 713 nm, the highest average power of 1.3 W is obtained, with a conversion efficiency of 37.1%. If both signal and idler powers are counted in, the total efficiency is 52%, which is a new benchmark. In addition, the compressed pulse duration is measured to be 108 fs at 788 nm, with a time-bandwidth product (TBP) of 0.46. The beam quality factors M² of 788 nm laser are measured to be Mx2=1.38 and My2=1.18, respectively.

Polarization converters for the generation of structured light beams, in particular, optical vortices, are widely used in various fields of science and applications. The search for affordable and adaptable (reconfigurable) systems that allow efficient conversion remains relevant. This paper discusses the formation of a polarization converter through optical modification of a thin layer of an amorphous azobenzene-containing polymer by exposure to a laser beam. Such a material exhibits optical anisotropy due to the redistribution of absorbing fragments caused by light-induced trans-cis transitions. It is shown that under the action of a light beam with an axially symmetric polarization distribution, a corresponding distribution of the induced optical axis is created with a high degree of locality. The induced anisotropy persists up to the melting point and can be rewritten by subsequent exposure to light.

Photon-number superposition states are a valuable resource for quantum information processing and can be deterministically generated using advanced quantum-dot (QD) platforms. Here, we propose a twin-field quantum key distribution (TF-QKD) protocol that employs photon-number superposition states of the form 1-t|0⟩+e^iϕt|1⟩. Numerical simulations show that the protocol outperforms existing laser-based TF-QKD schemes in secret-key rate and transmission distance, surpasses the repeaterless bound, enabling secure communication beyond 210 km under experimentally achievable conditions. A key advantage is its direct compatibility with existing QD technology. As integrated, solid-state, on-demand single-photon sources, QDs inherently provide high stability, scalability, and photon indistinguishability, making them well suited for deployment in large-scale quantum networks. Overall, our work demonstrates a practical pathway toward high-performance long-distance TF-QKD and highlights the broader potential of solid-state non-classical light sources for quantum networking architectures.