新加坡国立大学刘小钢团队近日通过子晶格重构实现超过500阶的光学非线性响应。2025年6月18日出版的《自然》杂志发表了这项成果。

材料对具有显著光学非线性的刺激的响应能力对于技术进步和创新至关重要。尽管已经开发出非线性超过60的光子雪崩上转换纳米材料，但进一步增强仍然具有挑战性。研究组提出了一种通过重建子晶格和扩展雪崩网络将光子雪崩非线性增加到500以上的方法。结果证明，主体材料中的镥替代会引起显著的局部晶体场畸变。这些扭曲加强了交叉放松，这是控制数量积累的关键过程。 

因此，光学非线性被显著放大，能够通过单束扫描显微镜进行亚衍射成像，实现33 nm（约为λ_Exc的1/32）和80 nm（约为λ_Exc的1/13）（其中λ_Exc是激发波长）的横向和轴向分辨率。此外，该研究表明，光子雪崩纳米晶体内部存在区域差异，其中光子雪崩性能在单个纳米粒子水平上因不同区域而异。这种效应，再加上极端的光学非线性，使纳米发射器能够使用简单的仪器以超出其物理尺寸的分辨率进行可视化。这些进步为超分辨率成像、超灵敏传感、片上光开关和红外量子计数开辟了新的可能性。

附：英文原文

Title: Optical nonlinearities in excess of 500 through sublattice reconstruction

Author: Chen, Jiaye, Liu, Chang, Xi, Shibo, Tan, Shengdong, He, Qian, Liang, Liangliang, Liu, Xiaogang

Issue&Volume: 2025-06-18

Abstract: The ability of materials to respond to stimuli with significant optical nonlinearity is crucial for technological advancement and innovation1,2,3. Although photon-avalanche upconversion nanomaterials with nonlinearities exceeding 60 have been developed, further enhancement remains challenging4,5,6. Here we present a method to increase photon-avalanche nonlinearity beyond 500 by reconstructing the sublattice and extending the avalanche network. We demonstrate that lutetium substitution in the host material induces significant local crystal field distortions. These distortions strengthen cross-relaxation, the key process governing population accumulation. As a result, the optical nonlinearity is significantly amplified, enabling sub-diffraction imaging through single-beam scanning microscopy, achieving lateral and axial resolutions of 33nm (about 1/32 of λExc) and 80nm (around 1/13 of λExc), respectively (where λExc is the excitation wavelength). Moreover, our research shows regional differentiation within photon-avalanche nanocrystals, in which photon-avalanche performance varies across different regions at the single-nanoparticle level. This effect, coupled with extreme optical nonlinearity, enables visualization of nanoemitters at resolutions beyond their physical size using simple instrumentation. These advancements open new possibilities for super-resolution imaging, ultra-sensitive sensing, on-chip optical switching and infrared quantum counting.

DOI: 10.1038/s41586-025-09164-y

Source: https://www.nature.com/articles/s41586-025-09164-y