发表机构
Nanchang University; Institute for Advanced Study, Nanchang University; National Laboratory of Solid-State Microstructures and College of Engineering and Applied Sciences, Nanjing University（南昌大学; 南昌大学高等研究院; 南京大学固体微结构物理国家级实验室与工程应用学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用平带准BIC共振的3R-MoS2超表面，通过超晶胞对称性破缺实现宽带角、高效SPDC光子对产生，发射角扩展至±5°，产率提升数个数量级，为动量无关量子光源提供新策略。
AI 中文摘要
超薄光学共振超表面中的自发参量下转换（SPDC）为集成量子光源提供了一个有前景的平台。然而，传统共振受到陡峭的动量色散的限制，将光子对产生限制在狭窄的激发和发射角度内。在此，我们展示了一种用于高效、宽带角SPDC光子对产生的平带共振3R-MoS$_{2}$超表面。通过采用布里渊区折叠实现的超晶胞对称性破缺策略，我们在近红外波段获得了一种平带准连续谱束缚态（quasi-BICs）共振，该共振在宽入射角范围内保持稳健的品质因子。利用共振的强局域电场增强和3R-MoS$_{2}$的大二阶非线性极化率，该超表面将简并SPDC光子对产生率提升了数个数量级，相比同等厚度的未图案化薄膜。关键在于，近零的带色散将有效发射角扩展到$\pm 5^{\circ}$，且光谱漂移可忽略不计（约0.1 nm），并具有高方向容差。在有限光谱带宽的脉冲激发下，光子对产率保持较高，展示了与准BIC共振的强光谱锁定，以抵抗泵浦失谐。这项工作建立了一种与动量无关的量子光源的通用策略，为无扫描量子鬼成像和空间频率量子处理开辟了新途径。
英文摘要
Spontaneous parametric down-conversion (SPDC) in ultrathin optical resonant metasurfaces offers a promising platform for integrated quantum light sources. However, conventional resonances suffer from steep momentum dispersion, limiting photon-pair generation to narrow excitation and emission angles. Here, we demonstrate a flatband-resonant 3R-MoS$_{2}$ metasurface for high-efficiency, broad-angle SPDC photon-pair generation. By implementing a supercell symmetry-breaking strategy via Brillouin zone folding, we achieve a flatband quasi-bound states in the continuum (quasi-BICs) resonance in the near-infrared regime that maintains a robust quality factor across a wide range of incident angle. Exploiting the strong local electric field enhancement of resonance and the large second-order susceptibility of 3R-MoS$_{2}$, the metasurface boosts the degenerate SPDC pair-generation rate with orders of magnitude enhancement over an unpatterned film of identical thickness. Crucially, the near-zero band dispersion extends the effective emission angle to $\pm 5^{\circ}$ with negligible spectral drift $\sim 0.1$ nm and high directional tolerance. Under pulsed excitation with a finite spectral bandwidth, the photon pair yield remains high, demonstrating strong spectral locking to the quasi-BIC resonance against pump detunings. This work establishes a versatile strategy for momentum-independent quantum light sources, opening new avenues for scan-free quantum ghost imaging and spatial-frequency quantum processing.
