基于光频双曲超材料的无标记远场超分辨显微成像

Label-free far-field subdiffraction imaging based on hyperbolic metamaterial

超分辨光学显微成像技术具有非接触、无损伤等优点。现有超分辨成像手段大多依赖荧光染料,限制其应用场合。近年来基于频谱平移原理的无标记远场显微成像手段被提出,但其分辨率受限于波导材料折射率。利用双曲超材料(hyperbolic metamaterials,HMM)的空间频率带通滤波特性,结合亚波长光栅,激发大面积均匀高频体等离激元(bulk plasmon polariton,BPP)照明场,得益于照明的高波矢量,物体的高频信息可以转移到传统成像系统的通带,为远场图像提供亚波长空间信息。基于该方法,采用0.85数值孔径标准物镜,532 nm波长下2.66k横向波矢的BPP照明中心距为100 nm双缝结构成像,横向分辨力提高至λ/5.32。进一步提高BPP的横向波矢可使分辨力提升至λ/7.82。该方法无需标记,便于与传统显微镜集成,为生物医学、芯片工业、材料科学等领域的应用提供了一种可视化的超分辨手段。

Super-resolution optical microscopy is an important technology due to the non-contact and nondestructive advantages.Currently,most of the super-resolution imaging methods rely on fluorescent dyes,which limited their applications.The label-free far-field microscopy imaging method based on the frequency shift effect has been proposed and developed in recent years.However,its spatial resolution is limited by the refractive index of waveguide materials.Based on the characteristic of optical spatial spectrum band-pass filtering in hyperbolic metamaterials(HMM),a large-area uniform bulk plasmon polariton(BPP)field with high spatial frequency can be achieved by combining with nano-scale gratings.Due to the large wave vector of the BPP illumination,the highfrequency information of the object can be transferred to the passband in traditional imaging systems and participate in super-resolution imaging.Illuminated by a BPP field with 2.66 kat a wavelength of 532 nm,a double-slit structure with a 100 nm-wide center-to-center distance has been resolved with a 0.85 numerical aperture standard objective based on this method.The lateral resolution is improved toλ/5.32.By further improving the transverse wave vector of BPP,it can be improved toλ/7.82.This design is label-free and conveniently integrated with traditional microscopes,which provides a visual super-resolution imaging method for applications in biomedicine,on-chip industry,material science,and other fields.